Characters / Cells at Work!

Inside every human body, there are roughly 37.2 trillion cells, each and every one working hard to maintain a healthy and effective system 24/7. And they all take their jobs very seriously.
Welcome to the inside of a human body.

Characters (or anthropomorphic representations of real cellular organisms) in Cells at Work! Beware of potential spoilers.

---

Cells in general

• Absurdly Dedicated Worker: All the cells will keep doing their jobs to make sure the body stays alive, no matter what happens.
• Anthropomorphized Anatomy: A manga/anime about Anthropomorphic Personifications of the cells inside a human body.
• People Farms: Cells are manufactured in facilities and raised by other cells until they are old enough to do their jobs.
• You Are Number 6: Each individual cell has a title and individual number. This is as close as they get to having names.

Main Characters

Red Blood Cell / Erythrocyte (AE3803)

^{Click here to see her as an Erythroblast}

Voiced by: Kana Hanazawa (Japanese), Cherami Leigh (English)

A red blood cell, often referred to as simply Red Blood Cell or AE3803. Like all red blood cells, her job is facilitating respiratory exchange and delivering nutrients throughout the body. She is new to her job and often gets lost or makes mistakes, but is nevertheless determined to do her best.

---

• Affectionate Gesture to the Head: Rather than a head pat, she playfully pokes the Platelet Leader in the cheek.
• All of the Other Reindeer: As a young erythroblast, her classmates teased her because of her tendency to get lost easily.
  Male Erythroblast: I bet that girl's gonna lose her way and get eaten up!
  Young AE3803: (frightened) Don't say that!
• Apologizes a Lot: She desperately apologizes to whoever she disturbs or tries to help her whenever she's lost.
• Astonishingly Appropriate Appearance: The protagonist red blood cell, who fittingly has a bob of bright red hair. No other red blood cell is seen with this hair color. According to flashbacks, she was chosen at birth to be a red blood cell by the Hematopoetic Stem Cells because of her hair color.
• Attention Deficit... Ooh, Shiny!: One reason she gets lost so often is because she stops to play with the Platelets, then forgets what she was doing and follows them wherever they are going, much to the chagrin of her kouhai.
• Audience Surrogate: Most of the time, Red Blood Cell asks various questions that the audience might have about the new types of cells they happen to meet.
• Blush Sticker: Not that noticeable, but she sports these to reflect on her Plucky Girl nature.
• Butt-Monkey: She has No Sense of Direction, combined with her clumsiness, and being a magnet for bacterial attacks. Poor girl can't catch a break.
• Comical Overreacting: Often lets loose a shrill scream when things go awry.
• Cool Big Sis: Acts as a sister to the Platelets, all too happy to set aside some time to play with them.
• Cute, but Cacophonic: She is prone to extreme freak-outs whenever she is startled.
• Cute Clumsy Girl: She often messes up, getting lost all the time, entering places she isn't supposed to, and sometimes crashes into others. This leads her to get flustered a lot and often she will freak out.
• Cuteness Proximity: Practically turns to mush whenever the Platelets are around.
• Damsel in Distress: She doesn't possess any weapon or way to defend herself (though in Chapter/Episode 1, she manages to pull a Bare-Handed Blade Block on Pneumococcus), so she's always at the mercy of hostile organisms in the body. Justified, as she is not a cell made to protect the body, but to transport oxygen. However, Red Blood Cells are great at running away, and AE3803 manages to improve at dodging bacterial attacks to the point where they can't lay a single claw on her.
• Defiant Stone Throw: She throws her nucleus (hat) against the 'Pseudomonas aeruginosa' when she was an Erythroblast. It doesn't do much damage, but lets her escape enough for U-1146 to find and defend her.
• Determinator: As klutzy and out-of-her-depth as she may be in many situations, she embodies the true spirit of a Red Blood Cell by never faltering once in her job to carry oxygen.
  • Exaggerated in Episode 8 where she is not only tries to get her job done, but is also determined to do it by herself without the help of White Blood Cell or Senpai Red Blood Cell, with both of them seeing her emanating a fiery Battle Aura showcasing her undying determination.
  • Exemplified best when she continues to trudge through a raging blizzard, brushing with death as the entire body undergoes hypovolemic shock.
  • And then again in the manga finale, where her undying devotion to service despite the cytokine storm helps to calm others.
• Failed a Spot Check: In episode 8, she somehow misses U-1146 above a sign that says "Straight ahead," in which the latter was deliberately helping her fulfill her tasks.
• Forgotten First Meeting: Turns out Red Blood Cell and White Blood Cell already met each other when they were still an erythroblast and a myelocyte (basically child cells) when a bacteria attacked the bone marrow they were staying in. However, they only met that once, so they don't remember each other's faces when they meet again as adult cells. Red Blood Cell considers the possibility White Blood Cell was the same myelocyte, but she dismisses it as that would be too much of a coincidence.
• Gut Feeling: Red Blood Cell's strand of hair tends to stand up straight if something bad is about to happen.
• Heroic Bystander: Red Blood Cells are not designed to combat bacteria and lack weapons^note That is to say, the only bacterial defense they do have IRL, would likely be something of a Suicide Attack, Heroic Sacrifice, or Dangerous Forbidden Technique at best and are taught to run on sight from any pathogens they encounter. Given her tendency to find herself getting caught up with pathogens, she has since become White Blood Cell's Sidekick of sorts and assists him however she can. She's also not completely defenseless: able to perform a Bare-Handed Blade Block on Pneumococcus, and even as an erythroblast she throws her hat at a Pseudomonas aeruginosa's eye to escape from it.
• Heroic Wannabe: As an erythroblast, she aspired to become a fully developed erythrocyte.
• His Name Really Is "Barkeep": Her full name is "Red Blood Cell AE3803".
• Hot-Blooded: Pun aside, once she feels she's had enough of relying on others she fully intends to finish her tasks without any help. Her friends even notice this.
• Idiot Hair: She has a strand of hair sticking out from the side which at times twitches with emotion. It's been around since the day she was born. On an interesting note, Red Blood Cell's strange ahoge and tendency to get lost may imply that she is a sickle red blood cell. However, it is not confirmed.
• I Just Want to Be Normal: She's all too conscious of how directionally challenged she is and would love nothing more than to be an efficient Red Blood Cell just like everyone else.
• Meaningful Appearance: All red blood cells wear berets that are shaped exactly like the real-life cells they represent. They wear similar hats as erythroblasts, with the only major difference being a pom-pom on top that represents the nucleus, which is pulled off when an erythroblast "graduates" to become a red blood cell.
• Meaningful Name: Her name AE3803 is a hexadecimal color for a shade of red.
• Meido: As with her fellow Red Blood Cells, she wore a Meido uniform as a child, up until she graduated from cell school.
• Naïve Newcomer: Is new to her job and it definitely shows. This benefits the story as it allows her to ask questions about the human body for the sake of the young audience's education.
• Nice Girl: As sweet-tempered as she is clumsy, and one of the few to outright thank White Blood Cell and his kind for their hard work.
• No Sense of Direction: She is hopelessly bad at traveling the body from the time she was an erythroblast, and regularly needs either White Blood Cell or AA5100, her Red Blood Cell senpai, helping her. She gets better as time goes on.
• Out of Focus: There are a few chapters throughout the series where Red Blood Cell does not make an appearance at all. She is most notably absent for nearly the entirety of Volume 3 (Chapters 11-14), where the focus is the supporting characters, and Volume 5 (Chapters 20-25), which covers the Lactic Acid Bacteria and Cancer Cell 2 arcs. Her usual role in Volume 5 as The Watson and Supporting Protagonist is taken by Ordinary Cell instead.
• Plucky Comic Relief: Her main shtick of No Sense of Direction plus her being a magnet for trouble is often the main source of comedy.
• Plucky Girl: Even after facing germs on a daily basis, getting lost, or nearly dying, she will determinedly bring oxygen to the cells in need.
• Red-Headed Hero: Her bright red hair is taken note of when she is born, and ultimately decides her job in the body.
• Red Oni, Blue Oni:
  • Puns aside, she's the more emotional and excitable red to White Blood Cell's more serious blue.
  • She's also the red to her much more methodical, serious, and professional kouhai's blue.
• The Scream: Frequently does this when she gets berated by other cells or encounters harmful invaders in the body, to the point where it's practically a Running Gag.
• Security Cling: To Senpai RBC when AE3803 gets introduced to NT4201, AE3803's new Kohai. It's too the point where AA5100 is grimacing in pain at the amount of force she's being clung to.
• Seen It All: By the time she is tasked to train a kouhai, she has spent so much time around White Blood Cells that their various shenanigans have become this to her, in contrast to the bewilderment of said kouhai seeing such behavior for the first time.
• Ship Tease: For whatever reason; despite being cells, belonging to the same body, etc., U-1146 and AE3803 have lots of affectionate interactions.
• Supporting Protagonist: Downplayed example. Both she and White Blood Cell share roles as protagonists, but her role in the body is more of a civilian/support function, whereas White Blood Cell fills the more traditionally heroic role of protecting civilians and defeating enemies. Additionally, she is also completely absent from a few chapters, whereas White Blood Cell has appeared in every chapter so far.
• Sweet Tooth: Since red blood cells don't have nuclei,^note and thus don't have mitochondria with which to produce energy they ingest glucose as a source of energy. This translates to Red Blood Cell being fairly fond of sweets.
• Tempting Fate: At the beginning of chapter 15, when AA5100 warns her that going alone in the body is a bad idea, she responds that the possibilities of a red blood cell running into danger is minimal. Not only does she end up attacked by a random bacterium, but after being saved by a monocyte, she comes face to face with the group of Staphylococcus Aureus.
• Tomboy and Girly Girl: The tomboy to Macrophage's girly girl because of her more masucline manner of dress and lacking the same feminine charm. In a twist, she's the one lacking in combat prowess and frequently in need of saving.
• Unskilled, but Strong: Has the innate determination to be an exemplary red blood cell, but is held back by her lack of experience navigating the body.
• Unstoppable Mailman: No matter how bad the situation is she never, ever gives up on delivering her package. Not even during hypovolemic shock or cytokine storms.
• Wall Run: Red Blood Cells are very skilled at running from danger, moving so fast that she can run along the walls.
• The Watson: Serves as this to White Blood Cell and other characters, asking questions and receiving explanations about the various cellular organisms and organs encountered.

White Blood Cell / Neutrophil (U-1146)

^{Click here to see him as a myelocyte}

Voiced by: Tomoaki Maeno, Tomo Muranaka (as a myelocyte) (Japanese), Billy Kametz, Erica Mendez (as a myelocyte) (English)

A White Blood Cell. Is usually referred to as Neutrophil or U-1146. Like all white blood cells, his job is to patrol the body and take down any invading organisms. U-1146 is aloof and stoic, but cares very much about the other cells.

---

• Amazing Technicolor Population: He and the rest of the Neutrophils have unnatural white skin, as much as the uniform they wear and their hair. He and the ones of his type are noticeably the only characters of the setting presented like this, since the other cells have a more realistic skin color.
• The Artifact: His name and character design indicates the fact that he (and his colleagues) were originally intended as the personification of all white blood cells, before all different types of white blood cells got their own personifications. Nowadays, his design is accepted as the personification of neutrophils.
• Beware the Nice Ones: Generally calm and nice, but as soon as invaders show up inside the body he can quickly switch into a murderous rage until all the threats have been neutralized.
• Big Brother Instinct: Has a very soft spot for the Platelets, offering them drinks and carrying them whenever there's trouble. Leader-Chan even calls him "Big Brother".
• Big Damn Heroes: He is usually the one to save AE3803 from trouble. Expect for him and his allies to pull this off once a chapter.
• The Big Guy: Like all defensive cells, his job is to protect the organism, fighting off all harmful cells with deadly force, and is also quite imposing in size.
• Blade Enthusiast: His main way of dealing with enemy bacteria and viruses are knives, which is a trait shared by all Neutrophils. They have two variants of them; some smaller ones designed to be thrown at the enemies that are equipped at the belt (that are rarely used, since it's necessary to have practice with them to avoid hitting fellow neutrophils), and six bigger knives (inspired by Russian "antiterror" knives) equipped at the legs and the hips, that are primarily used for combat.
• Blood Is the New Black: U-1146 is practically never seen without bacterial cytoplasm on his jumpsuit when a germ invasion is happening.
• Blood Knight: Quite literally. He and his kin are bloodthirsty fighters who live only to destroy the body's many invaders.
• Bromance: With U-4989. Typically seen together in their White Blood Cell squad. Additionally, U-4989 appears to care very deeply about U-1146, as seen in Chapter 27 of the manga.
• Casual Danger Dialogue: He happily agrees to Red Blood Cell's request to give an overview of immune cells to Kohai Red Blood Cell... while he's busy tearing apart and killing a germ.
• Catchphrase: The White Blood Cells share "Antigen sighted!" and "Die, germs!" as catchphrases when working. The former is for when they encounter a bacteria, and the latter is for when attacking.
• Character Focus: The second season of the anime adapts the volumes of the manga where Erythrocyte was largely Out of Focus in favor of the rest of the side characters. This effectively makes the Neutrophil the actual main character of the season. This gets reflected in the ED, where while it starts off as a large group shot, it slowly zooms in to focus on Neutrophil who's in the center.
• Childhood Friends:
  • With Eosinophil. They grew up in the same bone marrow.
  • Also with U-4989, U-2048 and U-2626. Asides from being classmates in Cell School and patrolling the same region as adult cells, there is also a picture of the four of them that was taken in a picture booth, complete with "BFFs" and sparkling eyes filters.
• Clothing Damage:
  • His clothes are often splattered with blood whenever he and his teammates fight bacteria and viruses. An omake shows that they could request new uniforms whenever their uniforms are torn.
  • Played for Laughs when he is activated by seeing embarrassing pictures of his past given by Dendritic Cell.
• Colour-Coded Characters: Taken to great extremes. He and other neutrophils don't only wear white clothes (the meaning of the color being purity and justice according to the extra material of volume 3), but they are also white themselves.
• Color Motif: White. This is The Artifact of being originally standing for all white blood cells.
• Combat Pragmatist: Not above using some tricks or calling reinforcements to beat opponents giving him a hard time.
• Creepy Good: Often seen as such, especially by Senpai Red Blood Cell and other non-immune cells. Despite his unnerving appearance, cold demeanor and unrelenting lust for the cytoplasm of pathogens, he does it all for the body's benefit and treats the other cells with professional courtesy.
• Cross-Popping Veins: While normally laid back and calm, even White Blood Cell gets ticked off at NK Cell and Killer T Squad Leader's bickering.
  T Cell Squad Leader: Stuff your sour grapes! I told you going off on your own was dumb!
  NK Cell: Shut your face dumbass! You two blockheads couldn't even spot that Cancer cell taking a stroll in public!
  Neutrophil: Cut it out you two! This isn't the time or place!
• Cuteness Proximity: Even he is charmed by the absolute adorableness of the Platelets.
• Detect Evil: Has the ability to detect invasive organisms such as bacteria thanks to a signal that emerges from the back of his cap when he's near them. All the Neutrophils have this.
• Determinator: He refuses to give up from fighting until the enemy is dead. Shown in Episode 10 while hanging for dear life from a cliff, he declares that even if the body is failing he won't give up in killing the Bacillus Cereus.
• Diving Save: With Memory B-Cell, Red Blood Cell and Senpai Red Blood Cell in episode 5 of the anime, when they're confronted by the Steroid. (In the manga, he's blasted along with them.)
• Due to the Dead: Numerous times, he is shown praying for all the dead cells who are killed by him and other white blood cells during virus attacks, as he laments that they had to be killed for the sake of the body.
• Eating the Enemy: He eats the pathogens he kills to identify them, and as a source of food (although they apparently don't taste good). White Blood Cells are also equipped with sprays that melt microbes down into more digestible parts.
• Eat Me: Pulls this strategy against the leader Vibrio bacteria in the fourth episode.
• Establishing Character Moment: The first chapter shows who he is and how he operates: he's very competent at his job, an overall okay guy to have around, and a bit socially isolated from non-immune cells.
• Face of a Thug: He normally has a very serious expression with a Thousand-Yard Stare, Creepy Shadowed Undereyes and with his face covered in shadows, but he is actually a nice fellow when not dealing with outside invaders. All of the Neutrophils have this, but he is recognizable from his partners due to the lock of hair covering his right eye.
• Fashionable Asymmetry: The very thing that distinguishes him from his peers is a lock of hair that covers his right eye.
• Fire-Forged Friends: With Killer T Cell Squad Leader and NK Cell during the Cancer arcs.
• Forgotten First Meeting:
  • Turns out Red Blood Cell and White Blood Cell already met each other when they were still an erythroblast and a myelocyte (basically children cells) when a bacteria attacked the bone marrow they were staying in. However, they only met that once so they don't remember each other's faces when they met again as adult cells.
  • He also once met Basophil when he was still a myelocyte. He was under the impression that Basophil was an Eosinophilic Band Cell.
• Friend to All Children: Always shows his soft side whenever he interacts with the Platelets.
• Good Is Not Soft: Around friendly cells he is a very decent guy, especially compared to most other immune cells, but put him near a pathogen and he won't hesitate to pepper his attack with vicious insults. Even when he took the time to show a moment of compassion toward Cancer Cell by hearing out his final words, he remained stone-face throughout and reminded him quite frankly afterward that he still must be killed for the sake of the body's safety.
• Go Through Me: Has done this many times, putting himself in harm's way to protect other defenseless cells. The first instance dated all the way back to when he was a kid myelocyte where he saved young Red Blood Cell back when she was an Erythroblast.
• Harmless Electrocution: Is electrocuted by Staph A's fibrin when she uses coagulase to incapacitate them. While severely wounded and dazed, he is still alive by the end of the ordeal.
• High-Pressure Emotion:
  • When he's exposed to embarrassing photos of his past.
  • Additionally, when he realized his beloved Band-Cell Senpai was actually still alive as Basophil and had heard all the embarrassing admiration U-1146 had made about him.
• His Name Really Is "Barkeep": His full name is "White Blood Cell U-1146, Neutrophil Division".
• Hitman with a Heart: Will kill germs without remorse, but has shown his soft side to other cells he knows, especially AE-3803. He also shows concern to his teammates and even understands Cancer Cell's plight which endears him to the latter.
• Humble Hero: Whenever he is thanked for his efforts in protecting the body and the other cells, he answers that he's simply doing his job.
• I Did What I Had to Do: He feels sorry for Cancer Cell, but has to kill him for the sake of the body. Cancer Cell understands this reasoning, but will not go down without a fight.
• Karaoke Box: According to one of the embarrassing photos of Dendritic Cell, he enjoys karaoke in his free time. In the photo, he is caught by Basophil, of all people.
• Kid Hero: Even back when he was a myelocyte, he tried to defend Erythroblast (young Red Blood Cell) from a bacteria in the bone marrow, with nothing but a toy rubber knife as his weapon.
• Kill It Through Its Stomach: Does this to an unfortunate Vibrio parahaemolyticus bacteria who has the bad idea to eat him in chapter 5.
• Light Is Good: Wears (and is) entirely white, and, behavior and appearance aside, he is a decent cell who fights for the well-being of the body and its inhabitants. Applies to the rest of the neutrophils as well.
• Like Brother and Sister: With Eosinophil, his childhood friend from cell school. As adult cells, they both regard each other fondly, and have shared mutual experiences.
• Mood-Swinger: According to U-4989 in chapter 26, he's the most emotional in the squad, swinging from joy to sorrow over trivial matters. In the beginning of the chapter, U-1146 vows to do his job without emotion and spends the rest of it excitedly watching the platelets work and yelling words of encouragement to Backwards-Cap platelet.
• Mr. Exposition: Typically provides answers and explanations to Red Blood Cell's questions regarding the different cells they meet.
• Non-Standard Character Design: Compared to everyone else, White Blood Cell looks like he belongs to a completely different anime, with featureless black eyes lacking light and unnaturally white skin while everyone else has a more realistic skin tone.
• No Social Skills: He has his moments, such as during episode 1, when AE3803 thanked him for saving her:
  "{Stoically} No need to thank me. I was only doing my job.
  [Beat]
  "No, I mean You're welcome."
• Not Helping Your Case: It is difficult for AE3803 to convince others that he's not a savage thug when he's tearing apart pathogens with his bare hands and teeth.
• Not Quite Dead: During the Cancer cell fight, Neutrophil is seen going motionless and seemingly dies under some rubble. It turns out he is just resting though.
• Not So Above It All: Although he tries to maintain a professional soldier-like manner, he does soften up and act friendly towards Red Blood Cell.
• Not So Stoic:
  • While he usually keeps a calm and almost aloof demeanor, he's smitten by the Platelets like everyone else.
  • He has a habit of breaking out rather lovely smiles whenever he's enjoying his downtime with Red Blood Cell.
  • He was a lot more emotional back when he was a Myelocyte, yelling out his catch phrases at the top of his voice.
  • He lost his cool demeanor when Dendritic Cell throws an embarrassing pic at him.
• Only Sane Man: He doesn't get involved in the squabbles of Killer T Squad Leader and NK, and tries to serve as a mediator to break up their fights.
• Precocious Crush: As a myelocyte, he greatly admired Basophil as a band cell, going so far as to give him leftover food and mourning his (seeming) loss.
• "The Reason You Suck" Speech: Along with U-4989, U-2048 and U-2626, he taunts the campylobacter on their faults, before assaulting them.
• Red Oni, Blue Oni: The calmer and more serious blue to Red Blood Cell's overemotional red.
• Rousing Speech: To NK Cell when she gets weakened by stress.
  Neutrophil: "NK!! Don't stop believing in yourself! We're pros! We've trained for this! If we work together, we can defeat any enemy!! Put your heart into it!! Get up!! Get up and run!!"
• Seeker White Blood Cells: White Blood Cells are quick, brutal, and efficient in their line of work.
• Sensitive Guy and Manly Man: The Sensitive Guy to Killer-T's Manly Man. He enjoys hanging out with other cells in the body and would like for them to understand and not be afraid of the immune cells, a sentiment which earned him a punch in the face when shared with Killer T. He has an especially big soft spot for AE-3803, to the point where he is willing to set time aside from his work to help or talk to her, something that Killer T wouldn't be caught dead doing. Downplayed, however, as he's still just as much of a tough-as-nails soldier as Killer T ever was and never once lets his soft side interfere with that.
• Series Mascot: While he and Red Blood Cell more or less share equal protagonist status, White Blood Cell is the one to consistently appear on the covers of the manga volumes.
• Ship Tease: For whatever reason; despite being cells, belonging to the same body, etc., U-1146 and AE3803 have these kind of interactions.
• Slasher Smile: The White Blood Cells are normally laid-back people, but when they encounter a bodily invader, they turn into ruthless, psychotic killers.
• So Proud of You:
  • His reaction when the directionally challenged Red Blood Cell finally manages to navigate the entire circulation system on her own.
  • He shows this again when he sees how determined Red Blood Cell is to be a good senpai to her kouhai.
• The Squad: Seems to form a squad, or patrols the same sector as U-4989, U-2048 and U-2626. This makes sense in terms of effective cohesion, as the four of them have been together since childhood.
• Stalker without a Crush: Ship Tease bordering on Stalker with a Crush levels aside, he followed AE3803 across her journey to complete a circulatory cycle, guiding her without being seen and protecting her from enemies. He even defends her from Killer-T Cell when he scoffs at her efforts.
• The Stoic: He is serious and professional most of the time, the only exceptions being when he is dealing with invaders or when he sees the Platelets.
• Stunned Silence: While not quite silence, Neutrophil is only able to utter "Eh? Eh?" in astonishment after being punched by Killer T Squad Leader.
• Super-Persistent Predator: It's in his nature as a White Blood Cell, but his microbe-detecting receptor and his ability to transmigrate through cell tissue allow him to chase germs to the ends of the body.
• Surprisingly Elite Cannon Fodder: Neutrophils are the first line of defense of the immune system and they are not expected to last long against external threats. U-1146, however, thanks to both experience and luck (as well as his professionality and determination), manages to survive every kind of deadly situations (including some incidents where numerous other neutrophils have died, like the pimple incident in chapter 14), making him a tough individual of his kind.
• Taking the Bullet:
  • In episode 8, he blocked a bacteria's spikes with his arm to protect AE3803.
  • In chapter 23, he took a surprise attack meant for Killer/Memory-T. This allowed Cancer Cell to capture him in a container making him unable to help NK and Memory-T from Regulatory-T's beatdown.
• Tranquil Fury: Combined with a Death Glare when he finally catches up with the Bacillus Cereus. He takes his sweet time killing the bacterium.
• Two Guys and a Girl: With Killer T Squad Leader and NK. Acts as the mediator of the group.
• What the Hell, Hero?: To NK Cell when she tricks Killer T Squad Leader into running into antibody fire.
• When She Smiles: While he is serious most of the time, he can put some nice smiles from time to time. One example being chapter 10, when he explains to Killer T Cell that it would be nice if, someday, red blood cells and cells of the immune system would get along well despite their differences.
• White Shirt of Death: His stark white hair, skin, and clothes make the blood that gets spilled onto them look very obvious.
• Worf Had the Flu: He had a hard time catching the Bacillus Cereus thanks to suffering heat stress. Once he was able to cool off, he has no trouble dispatching it.

Immune System

Killer T Cell (Squad Leader)

^{Click here to see him as a T-Cell Trainee}

Voiced by: Daisuke Ono, Mariko Higashiuchi (as a thymocyte) (Japanese), Robbie Daymond, Kimlinh Tran (as a thymocyte) (English)

A Killer T Cell. Like other cells of his ilk, he is responsible for killing infected, cancerous, or otherwise damaged cells. Sometimes referred to as Killer T Cell Squad Leader, as he's usually seen leading other T-Cells. He is rather harsh and takes his job very seriously.

---

• Authority Sounds Deep: He's a Frontline General who fights off invading germs and his voice is so deep that he borders on being a raspy one
• Being Personal Isn't Professional: He gets angered at White Blood Cell upon hearing the latter get all sappy and admiring the work of Red Blood Cell. He punches White Blood Cell to the ground and lectures him that as immune cells, they are assassins who would never hesitate to kill and should never partake in sentimental activities like other cells do. However, it's implied that this is mostly because he's jealous of other immune system cells for being able to get along well with civilian cells.
• Berserk Button: Having embarrassing pictures of himself as a T Cell trainee being shared, when NK pushes him into the water/making him run into a cart, when he sees Neutrophil getting along with "non-immune" cells, to name but a few.
• Calling Your Attacks:
  • Has one when he was a kid, which he is embarrassed when Helper-T shouted it in his test.
    Helper T Cell: "Ultimate Secret Technique! Antigen Super Pummeling Smashing Fist!"
    Killer T Cell: "How the hell did you know that?"
  • He's shown to have prepared another called attack in the Return of Cancer Cell arc:
    Killer T Cell:"T-Cell Perforin Cannon Punch!"
• Captain Smooth and Sergeant Rough: The latter in this case, as a subordinate of Helper T Cell. Killer T Squad Leader tends to be loud and brash with his fellow Killer T Cells and downright harsh with the naive cells under his trainee. This is in stark contrast to the more "refined" Helper T Cell.
• Childhood Friends: While not exactly friends, he was in the same graduating class at Thymus school along with Helper T Cell and Regulatory T Cell.
• Crossdresser: Can be seen in a dress in one of Dendritic Cell's photos.
• Cross-Popping Veins: Put him and NK together, and you get this quite often.
• Curtains Match the Windows: Has dark yellow eyes and blond hair.
• Dark Is Not Evil: Despite wearing black and being kind of an ass, he fights for the well-being of the body and its inhabitants. Applies to the rest of Killer T Cells as well.
• Diving Save: Does this for Neutrophil and NK during the Cancer II Arc. Explained by Killer T being able to predict Cancer Cell's attacks.
• Drill Sergeant Nasty:
  • Is this to Naive Cells. He calls his trainees maggots and throws one of them into a window on the second floor of a building from the ground, and also belittles Naive Cell when he's unable to kill even one influenza cell.
  • Additionally, his training regimen includes of at least 1,865 pushups, 2,466 sit-ups and 3,580 pull-ups.
    Killer T Cell: "We don't need wimps in the T Cell squad!!! T Cells are the last resort of the immune system! Do you take that seriously maggots!!?! You think a last resort can be weak?!! Train hard you morons!!!
• Emergency Weapon: Kinda inverted in a way: Killer T mainly uses his fists to eliminate foreign threats, but he pulls out a knife when trying to kill Cancer Cell.
• Fire-Forged Friends: With Neutrophil and NK Cell during the Cancer arcs.
• Frontline General: He's commander of the T-cells and fights with them on the frontlines unlike Helper T-Cell who gives orders from behind a desk.
• Good Is Not Nice: Despite his rude behavior and abrasive personality, he plays an important role inside the immune system and is a professional who tries his best to defeat threats that can damage the body.
• Good Old Fisticuffs: Unlike other immune cells, T-cells like him, Effector, Helper, and Regulator fight with their bare fists.
• Gratuitous English: Killer T Cell uses one or two when addressing Naive T Cell. His subordinates do so more often.
  Random T Cells: "Yes sir!"
• Green-Eyed Monster: He's not jealous at all that White Blood Cell can have such a friendly relationship with civilians like Red Blood Cell. Nope, no siree.
• Hand Blast: His "secret attack" move is essentially using the force of his punch to generate a wave the size and shape of an enormous fist.
• Hard Work Hardly Works: Averted. His determination in staying at boot camp and becoming a full fledged T-Cell pays off. Although he did get Helper-T's help at the positive selection test.
• Headbutting Heroes: This with NK Cell and Helper T Cell. Based on their shared origins as NK/T Progenitors, this could also be construed as Sibling Rivalry.
• Large Ham: Extremely hammy and makes sure to let his presence be known when charging at invading pathogens.
• Lightning Bruiser: Can hit fast and hard enough to make an Influenza Virus go splat. After promoting to a Memory Cell, he can punch fast enough that even Cancer Cell cannot dodge his attack.
• Megaton Punch: At Thymus, Killer T was tricked into practicing a move that did not exist. He managed to perfect this imaginary technique and used it on Cancer Cell to devastating effect.
  Killer T Cell: "Take THIS! T Cell Perforin Cannon Puuunch!!"
• Mildly Military: The T Cells seem to be this as opposed to the White Blood Cells being policemen, though the former are dressed more like SWAT officers than soldiers.
• My Significance Sense Is Tingling: When Dendritic Cell is showing Naive T-Cell embarrassing old photos of the older T Cells from their younger days, at the same time, the T Cells immediately start getting goosebumps and chills.
  Killer T Cell: It feels like the dark past that we sealed away has been released!!
• Not Quite Dead: During the Cancer cell fight, Killer T Squad Leader is seen going motionless and seemingly dies under some rubble. It turns out he is just resting though.
• Not So Above It All: Despite his no-nonsense attitude and professionalism, he gives up and joins the Ordinary Cells in their badminton play at the end of chapter 11.
• Prescience by Analysis: When he becomes a Memory T Cell against Cancer Cell the Second, having previously battled against Cancer Cell.
• Rank Up: The Killer T Cell is shown to have been promoted to Memory T Cell during the Lactic Acid Bacteria Arc. NK and U-1146 still calls him Killer-T.
• Rule of Pool: Killer T Cell gets kicked into a pool... of large intestinal fluid by none other than NK Cell.
• Sensitive Guy and Manly Man: The Manly Man to U-1146's Sensitive Guy. He believes that every immune cell should be able to strike without remorse and that being friends with other cells will not let them do their jobs properly. He also is very ruthless in killing enemies, and during training, he threatens his team to be sent to the spleen if they fail.
• Sergeant Rock: Is referred to as a Killer T Cell squad leader (Chapter 19), basically embodies the trope as a whole.
• Sitcom Archnemesis: He has this dynamic with NK Cell despite both being Immune Cells that protect the body. Usually Killer-T is the target of NK's harassment, though he will fight back when provoked enough. But when push comes to shove, they can work together quite well, as seen in the Return of Cancer Cell arc.
• Took a Level in Badass:
  • His backstory is basically this. He was at first a weak and fearful Naive T Cell, but training and experience eventually shaped him into one of the biggest badasses of the immune system.
  • He undergoes another one when he is promoted to Memory T Cell in the second Cancer arc, being able to throw a punch that shoots shockwaves in the shape of a fist.
• Training from Hell: Throws one of his trainees into a window. Justifies this to Helper T Cell by saying he doesn't want wimps for fighters, incapable when they actually have to fight bacteria. In a way, this is Truth in Television, as, in a body that's healthy, only a small fraction of immature T-Cells should actually survive the "training" they get in the thymus. Additionally, his training regimen includes at least 1,865 pushups, 2,466 sit-ups and 3,580 pull-ups.
• Tsundere: A platonic Type A (Harsh). A Drill Sergeant Nasty who belittles the idea of immune cells befriending non-immune cells, but it’s obvious he’s in denial about his own desire to have non-immune cell friends.
• Two Guys and a Girl: With Neutrophil and NK. Acts as a foil to NK.
• Volleying Insults: Hand slipping and senility with NK Cell.
  NK Cell: Oops! My hand slipped!
  Killer T Squad Leader: My bad, my foot slipped!
  NK Cell: Sorry! My elbow slipped!
  Killer T Squad Leader: That's too much slipping! You going senile or what?
  NK Cell: You're one to talk!
  Killer T Squad Leader: I'm gonna kill you!
  NK Cell: Huh! I'd like to see you try it!
• Would Hit a Girl: Dishes out some pretty vicious blows to NK Cell during their fight. To be fair, she started it.

Macrophage / Monocyte

^{Click here to see her as a Monocyte}

Voiced by: Kikuko Inoue (Japanese), Laura Post (English)

A Macrophage cell, referred to as Macrophage. A type of white blood cell, she has many roles within the immune system, and is depicted as a sweet and motherly woman in a maid outfit who wields a meat cleaver with terrifying ease.

---

• Action Girl: Oh so much. Just ask those outside organisms butchered by her.
• Astonishingly Appropriate Appearance: Macrophage is very tall and wears a large hoop skirt; real macrophages are very large compared to other cells.
• Badass Teacher: Macrophages are also in charge of teaching and training young erythroblasts as they differentiate and mature into red blood cells. Combined with their combat skills, they also serve as their protectors. This is true of real life Macrophages, which are antigen presenting cells, and thus help 'teach' the body to create antibodies and other means of destroying a specific pathogen.
• Beware the Nice Ones: She might be one of the kindest characters in the series, being protective and motherly, but she's one of the most powerful immune cells around and can cut up germs with ease.
• BFS: Her weapon is a giant meat cleaver. It's thick enough for her to leave it standing upright despite not having a pointed head.
• Big Damn Heroes:
  • In chapter 15, when the neutrophils are about to be killed by the fused form of the Staphylococcus aureus, she and other macrophages emerge from the blood stream (as monocytes) just in time to finish the bacterium and save the day.
  • In episode 7 of the anime, just as Killer T Cell, NK Cell, and White Blood Cell look done for at the hands of Cancer Cell, she throws her cleaver and hits one of his wings, signalling the arrival of The Cavalry.
• Big Eater: Extra material from chapter 21 about phagocytosis reveals that she eats a lot of germs. This likely alludes to how her name literally means "big eater" in Greek.
• Catchphrase:
  • As a Macrophage: "Ara ara..." / "Oh, my...", as well as "Minasan..." / "Everyone..."
  • As a Monocyte: "Nice."
• Cool Big Sis: In addition to being a caretaker to the young erythroblasts, she's also very motherly and protective to pretty much every cell she comes across.
• Curb-Stomp Battle: She and her squad give one to the Staphylococcus aureus of chapter 15. The poor bacterium didn't stand a chance...
• Cute and Psycho: A very beautiful woman... who is also very enthusiastic in killing whatever thing invades the body.
• Dance Battler: She spins and twirls gracefully as she cuts and smashes bacteria invaders up, all with a sweet smile on her face.
• Dissonant Serenity: She doesn't drop the maid mannerism while in the middle of butchering a whole Zombie Apocalypse.
• Do-Anything Soldier: She functions as a soldier, janitor, daycare worker, teacher, cook, and even a spy!
• The Dreaded: Best shown in chapter 15. The revelation that they're dealing with Macrophages is enough to get all but one of the surviving Staphylococcus aureus to flee in terror.
• Eating the Enemy: The cleaver is not merely for show. Microbes that are too large for other white blood cells to eat are cut by Macrophage into smaller pieces and thrown into a cooking pot for consumption.
• Girl with Psycho Weapon: A maid dragging around a giant, crooked meat cleaver. Other Macrophages are shown wielding equally psychotic weapons like axes or hammers.
• Hazmat Suit: Macrophages wear these when they occupy their alternate role as monocytes and patrol the blood stream.
• Hidden Buxom: She's quite well-endowed, and how she and the other Macrophages manage to hide their figures while in Monocyte mode is anyone's guess. Justified since Hazmat equipment is quite bulky and feature concealing, and in her own words, "a maiden has to have a secret or two".
• Hollywood Acid: Monocytes carry sprays that easily dissolve bacterial invaders.
• Improvised Weapon: In "Common Cold," the Macrophages' weapons are replaced with sports equipment, including a tennis racket and surfboard. They use them anyway to eradicate the cold-infected cells.
• Kicking Ass in All Her Finery: Slaughters bacteria with a meat cleaver while wearing a maid dress with a huge poofy skirt.
• Lady of War: Never ceases to be the embodiment of feminine charm, even when brutally slaughtering hordes of pathogens. Taken to hilarious extremes in episode ten, in which every blow the macrophages deal against the invading army of Staphylococcus bacteria is punctuated by cherry petals and anime sparkles.
• Master of All: "All" is an overstatement, but the sheer diversity of the roles she can perform is still astounding. Even more astounding is that she is also extremely good at every single thing she can do. This is actually Truth in Television, as real life Macrophages perform numerous jobs and are incredibly versatile.
• New Job as the Plot Demands: She's a daycare worker, a cleaner, and also an assassin. While it's not emphasized, she also plays a role in gathering information on antigens, making her a spy as well! Justified, as real life Macrophages are incredibly versatile cells that perform numerous roles.
• Ninja Maid: The macrophages are depicted as gentle women in maid dresses who are constantly smiling. They also wield large weapons like machetes and can easily slaughter bacteria and other invaders.
• Older Than They Look: Assuming it's the same one, this particular Macrophage was shown to have been around since AE3803 was an erythroblast and when Killer T Squad Leader, Regulatory T Cell and Helper T Cell were young Killer T Cell Trainees. It appears that she also taught NK Cell when the latter was a Cell School student.
• One-Man Army: She can easily kill groups of enemies all by herself, as shown when she easily kills many influenza-infected cells without a sweat. Now imagine a crowd of macrophages ganging up on bacterial invaders...
• Perpetual Smiler: She's virtually always seen smiling.
• Samus Is a Girl: When she's patrolling the blood vessels, she takes the role of a Monocyte. As in, those guys in the Hazmat Suits that completely obscure their faces, figures, and gender. Monocytes patrol the bloodstream after maturing in the bone marrow and become macrophages after going outside the bloodstream and into a nearby tissue. AE3803 is flabbergasted when she finds that out.
• Silk Hiding Steel: Appears very demure, polite, elegant, and wears elegant dresses. Also one of the most powerful and combat-effective cells in the entire body when it comes to fighting harmful organisms.
• Sword Drag: Does it with her meat cleaver in the beginning of episode 3.
• Unflappable Guardian: Nothing anyone does seems to break her normal demeanor. Someone swapped all her weapons for sports equipment? She's strong enough even without her weapons, so this might be a nice change of pace. Trying to blackmail her with embarrassing photos of her past? How nice, a lovely trip down memory lane.
• Tomboy and Girly Girl: Within the context of the Immune System, she's the girly girl to NK's tomboy — NK being far rougher in demeanor than she is, and often butt-heads with other immune cells.

Helper T Cell / T Lymphocyte

^{Click here to see him as a T Cell Trainee}

Voiced by: Takahiro Sakurai, Mikako Komatsu (as a thymocyte) (Japanese), Ray Chase, Erika Harlacher (as a thymocyte) (English)

A Helper T Cell, sometimes referred to as Helper T or Helper T Commander. He is responsible for coordinating the immune response to specific threats.

---

• Artistic License – Biology: From a real life perspective, Helper T Cells do not directly combat pathogens and only direct other immune cells to the site. However the Cells at Work version of Helper T Cell is revealed to be quite capable of combat himself and at one point was strong enough to beat up Killer T Cell. (Then again, these cells go through the same training as all the other T Cells do...)
• Asskicking Leads to Leadership: He didn't become commander by being a slouch. He graduated at the top of his class at Thymus School and can still lay a beatdown if the time comes.
• Berserk Button: Having embarrassing pictures of himself as a T-Cell trainee being shared.
• Captain Smooth and Sergeant Rough: The former in this case, as the superior of Killer T Cell. Helper T is rarely seen outside of his office, and gives orders from behind a desk. He is often seen drinking tea and eating snacks. This is in stark contrast to the rougher behavior of Killer T Cell Squad Leader.
• Childhood Friends: While not exactly friends, he was in the same graduating class at Thymus school along with Killer T Cell and Regulatory T Cell.
• Headbutting Heroes: This with Killer T Cell. Based on their shared origins as NK/T Progenitors, this could also be construed as Sibling Rivalry.
• Hidden Badass: He used to be one of the best T Cell trainees, and could easily beat up the now Killer T Cell. However, as a Helper T Cell, he is never involved in combat, and spends most of his time drinking tea in the control room. However he hasn't really lost his combat skills, it's just that he rarely has the chance to show it.
  • Chapter 12 emphasizes this by referring to Helper T's physique as "loose," compared to Killer T's "Flex."
    Killer T Cell: "You're just sipping tea when we're putting our lives on the line out there!"
    Helper T Cell: "Oh come oooooooon. Office work is pretty hard. You wanna try it? You wanna swiiitch?"
  • But right after this exchange, Helper T Cell shows that he hasn't lost all his combat moves as he and Killer T Cell gang up on Dendritic Cell in the hopes of confiscating (and burning) all the embarrassing photos of their Thymus school days.
• Jerk with a Heart of Gold: Was this during his time as a thymocyte. He was rude and abrasive with his partners, but still gave advice to the thymocyte who would become the Killer T Cell Squad Leader after seeing his desire to become stronger. Not applied to his current status as Helper T Cell, as he is now polite and professional.
• Non-Indicative Name: Is depicted as a commander rather than a 'helper'. Truth in Television as many cell biologists have stated the naming of Helper T Cells is very misleading and not representative of their actual function.
• Officer and a Gentleman: Drinks tea often, dresses and functions like a commander, and spends all his time in the office.
• Stronger Than They Look: He looks and acts like an intellectual nerd, but as a trainee, he was actually stronger than Killer T Cell.
• Sweet Tooth: He's often seen eating cookies with his tea, and puts lots of sugar into his drink.

Regulatory T Cell

^{Click here to see her as a T Cell Trainee.}

Voiced by: Saori Hayami (Japanese), Erica Mendez (English)

A Regulatory T Cell, who acts as an assistant to Helper T Cell. This is reflective of their real-life role as immune system modulators. She is sometimes called Ms. Regulatory T Cell.

---

• Abnormal Limb Rotation Range: Is apparently able to rotate her entire body to the side at a 120 degree angle to the right. Aforementioned action was accomplished within a split second, and without moving her feet.
• Action Girl: She survived the Training from Hell when she was a kid. This is shown in full force in the Return of Cancer Cell arc, as she's able to beat up both Killer-T and NK Cell.
• Broken Record: "No you mustn't attack a cell."
• Childhood Friends: While not exactly friends, she was in the same graduating class at Thymus school along with Helper T Cell and Killer T Cell.
  Regulatory T Cell: "Those two... ...really haven't changed a bit..."
• Curtains Match the Window: Has blonde hair and yellow eyes.
• Emotionless Girl: Does just about everything deadpan, even as a T Cell Trainee. She retains the same attitude in the Cancer Cell II Arc, but she's shown to be Not So Stoic right before she dodges Killer T's attack.
• Excuse Me While I Multitask: During the Cedar Pollen Allergy arc, she can be seen holding three phones at once, two in one hand, and one against her head.
• Face–Monster Turn: She protects Cancer Cell the Second under the impression that he's a regular cell. However, she realizes her mistake when Memory T Cell manages to land a giant hit. This is representative of the way real life regulatory T cells are attracted and trafficked to cancerous tumors, hindering the body's immune response to cancer and creating poor prognosis in many cancers.
• Girl Friday: Acts as the more level-headed assistant and aide to Helper T Cell.
• High-Speed Missile Dodge: Does this when Killer T unleashes his "T-Cell Perforin Cannon Punch". Literally bends over by a full 120 degrees to her right without moving her feet, to avoid being hit by Killer T's attack.
• Hypercompetent Sidekick: While commander Helper T Cell is no slouch, no one was expecting just how much ass Regulatory T Cell was able to kick during the Return of Cancer arc. She's able to fend off attacks from NK and Killer T Squad Leader simultaneously, two of the more competent and lethal immune cells.
• Kick Chick: Uses her hands exclusively for blocking, while snapping out kicks to attack, including flip kicks and handstand kicks.
• Magic Skirt: Doesn’t show anything, despite her high-kicking fighting style.
• Not So Stoic: Regulatory T Cell deflects much of the attacks on Cancer Cell by Killer T quickly, efficiently and according to herself, without emotion. However when Killer T announces that he's about to unleash his T-Cell Perforin Cannon Punch, she has a flashback to her time in Thymus School as a classmate of Killer T, when he was initially "taught" the move. After this flashback, she drops her stoic expression and dodges the attack, allowing Cancer Cell the Second to be hit by the attack. Whether this was out of self-preservation or genuine emotional influence is up to the reader, though it is very much implied to be the latter.
• Number Two: She tends to be the one who assists Helper-T cell in emergency situations.
• Obstructive Bureaucrat: A literal example when she physically obstructs and blocks attacks from Killer T Cell and NK Cell to defend Cancer Cell 2, since she believes him to be a normal body cell, and is obligated by her role to protect such cells.
• Ojou Ringlets: Has two long ones on either side of her face. Had them ever since she was a T Cell Trainee.
• Prim and Proper Bun: She wears her hair in a bun, fitting with her calm and professional demeanor.
• "The Reason You Suck" Speech: Gives one to Killer T Cell when he tries to get past Regulatory T Cell in order to attack Cancer Cell the Second.
  Regulatory T Cell: Yes... You've always been the same. Bad at strategy... and swayed by emotion. Unable to feed off victory, nor to rise above defeat. You've always been like that. You will never defeat me. Your struggle is futile. Give up and cease your attacks.

Eosinophil

^{Click here to see her as an Eosinophilic Myelocyte}

Voiced by: M.A.O. (Japanese), Kayli Mills (English)

An Eosinophil Cell. Referred to as Eosinophil. Unlike other types of white blood cells, she's ineffective at killing bacteria and other pathogens (and is initially insecure about it), but can expertly eliminate parasitic organisms.

---

• Action Girl: She can't kill a bacterium to save her life, but when it comes to eliminating parasites, she has no rival.
• Adaptational Badass: While the manga depicts her as an immune cell completely specialized for dealing with parasites, she can fight a cancer cell without any problems in the anime. Maybe the anime made this decision because Cancer is essentially a giant parasite, so Eosinophil would do just fine. This actually has some real life basis, as research does suggest Eosinophils may play a role in the body's anti-cancer response.
• Aw, Look! They Really Do Love Each Other: When she decides to take on the Anisakis worm on her own, the other cells try to stop her, stating that while they did make fun of her, no one actually wants her to die on what they believed to be a Suicide Mission.
• Childhood Friends: With Neutrophil. They grew up in the same bone marrow.
• Crippling Overspecialization: She excels at slaying parasites, but is completely incapable of slaying even a single bacterium (which appear in the body much more frequently).
• Curb-Stomp Battle: Gives an awesome one to the Anisakis worm. She slays it with just one hit of her weapon!
• Curtains Match the Window: Has blonde hair and yellow eyes.
• David vs. Goliath: This basically defines her job description. When facing bacteria around her size that can be killed by any other white blood cell, she's completely hopeless, but against giant parasites that are almost invincible to other white blood cells, she can near effortlessly bring them down.
• Deathbed Confession: As a child, she secretly noted down difficult phrases in her books and wrote poetry. She quietly admits she still does it as an adult. She notes how difficult it was to admit it, even in the face of her death.
• Determinator: Despite knowing that she can't beat them, she never retreats when bacteria or other non-parasitic organisms are attacking the body, giving her best to try to defeat them. Unfortunately for her, in these cases, she ends up defeated and saved by other white blood cells.
• Eating the Enemy: The narration mentions she can do phagocytosis (a process when cells like neutrophils eat and delete bacteria and other external agents) just like the neutrophils. She, however, mentions that her phagocytosis is very weak. This is kind of reflected in her physical build: she's very thin and lightly built.
• Embarrassing Old Photo: She gets incredibly shy when she gets praised. Apparently, she doesn't like people to see this side of her, as she quickly snaps after she realizes how she is behaving in front of the other cells after she defeats the anisakis, and Dendritic Cell has a photo of her blushing while being praised as a part of his embarrassing photo collection.
• Forgotten First Meeting: She doesn't recognize Basophil as the sempai she admired when she was still a myelocyte. To be fair, she was under the impression that Basophil was an Neutrophilic Band Cell.
• Girlish Pigtails: Her hairstyle features two blonde twintails. It's very cute.
• Glass Cannon: Is pretty weak and gets knocked over after being struck twice by a lesser bacteria. However she is able to one-shot Anisakis when the parasite appears.
• Heroic Self-Deprecation: Eosinophil as pretty low self-esteem, which probably resulted from foreign bacteria and other cells looking down upon her and mocking her for her inability to effectively combat threats.
  Eosinophil: "It's fine. I know that I'm weak. Thanks for saving me."
• Hero with Bad Publicity: She works hard to protect cells from invading pathogens, and those cells like to whisper behind her back about how useless she is for failing every time. Fortunately, they change their tune once they see how effective she is against parasites; they all sing her praises and thank her for saving them.
• High-Pressure Emotion: When she realized her beloved Band-Cell Senpai was actually still alive as Basophil and had heard all the embarrassing admiration Eosinophil had made about him, her entire face turns bright red. Additionally, this happens whenever she gets praised.
• Like Brother and Sister: With Neutrophil, her childhood friend from cell school. As adult cells, they both regard each other fondly, and have shared mutual experiences.
• Luminescent Blush: Sports both this and Blush Sticker while being praised after defeating the anisakis at the end of chapter 5/episode 4.
• Not So Stoic: She always has a serious and melancholic expression (due to being mocked by other cells due to her uselessness when she fights against non-parasitic threats), but gets very shy and happy when she is praised.
• Precocious Crush: When she was still a myelocyte, she greatly admired Basophil as a band cell, going so far as to read difficult books with him and mourning his (seeming) loss. She also considered him to be very handsome.
• Prongs of Poseidon: Her weapon of choice is a bident, and based on the Anisakis she ends up facing, the parasites she's made to face have an aquatic beast theme to them.
• Smurfette Principle: She is tangentially a part of U-1146's gang, and is the only girl in their group.
• This Looks Like a Job for Aquaman: The chapter that introduces Eosinophil shows that while she's not very good at fighting bacterial infections, she excels at dealing with larger threats like multicellular parasites.
• Took a Level in Badass: As a myelocyte, she was terrified of the bacteria puppets she trained against. Thanks to the guidance of U-1146 and gang, as well as Basophilic Band Cell, she was able to overcome her fears and fight bravely against bacteria (though she's not very good at it).

Basophil

^{Click here to see him as a Basophilic Band Cell}

Voiced by: Tomokazu Sugita (Japanese), D.C. Douglas (English)

A Basophil Cell. Referred to as simply Basophil. He is supposed to be a type of White Blood Cell yet no one is sure what exactly his job is, but he is good at giving wordy, long-winded speeches.

---

• Cold Ham: He speaks in a bombastic and poetic way, but never raises his voice, even when outside organisms are attacking the body.
• In the Hood: His outfit features a raincoat that covers his head with a hood.
• Killed Mid-Sentence: Non-fatal example in chapter 16. Just when he was giving Mast Cell a motivational speech when she was doubting herself after the complaints that the Ordinary Cells gave her previously in the chapter (in his own particular way, of course), he is blown away by the gust of a dengue-infected Langerhans Cell (along with Eosinophil) before he can finish his speech. He still manages to motivate Mast Cell, who saves the day at the end.
• Oracular Urchin: Due to his function being poorly understood, he's depicted as a creepy hobo who spouts poetic phrases about current events. Despite this, his ramblings are given a great amount of weight.
• The Paragon: To Neutrophil and Eosinophil. For the former, Basophil taught him to think more deeply about his purpose in life. For the latter, Basophil taught her to note difficult phrases in her books, and influenced her to write poetry, even as an adult. For the both of them, Basophil's (seeming) sacrifice encouraged them to step forward into battle, despite the odds and certainty of the outcome.
• Parasol of Pain: He always carries an umbrella (to cover himself from the histamine that Mast Cell releases), that is also implied to be his weapon of choice.
• Pretty Boy: He has a delicate figure and long eyelashes. Eosinophil calls him handsome when they first met.
• The Reveal: He is the mysterious band cell senpai that a young U-1146 and Eosinophil befriend in chapter 27.
• Rousing Speech: Gives one to Mast Cell in chapter 16 in order to motivate her after she was doubting herself after the numerous complaints that other cells gave to her due to her way of acting. Of course, being Basophil, his long speech is confusing and ambiguous. Eosinophil interprets this as a way of telling Mast Cell to follow her own beliefs.
• Sesquipedalian Loquaciousness: His long-winded speeches sound like this, causing much confusion amongst other cells and forcing them to create their own interpretations of his messages.
• What, Exactly, Is His Job?: All that's known for certain is he's supposed to be a type of White Blood Cell, but to what purpose is unclear.

Natural Killer Cell (NK)

^{Click here to see her as a Cell School student}

Voiced by: Toa Yukinari (Japanese), Morgan Berry (English)

A Natural Killer Cell. Often referred to as NK.

---

• Action Girl: Any time NK encounters foreign organisms or cancer cells. It's emphasized by how she's often drawn with some serious muscle tone on her.
• Aloof Dark-Haired Girl: She has short black hair and is considered a wild card by other cells and prefers to fight alone.
• Amazonian Beauty: She has a well-built muscular body, even if nowhere near the level of Killer T Cells, but those muscles do nothing to prevent her from being just as attractive as the other "young adult female"-looking cells, though with more of a handsome feel than a cute or beautiful one.
• Ass Kicking Pose: Does this often in the second cancer cell arc. Is called out for it by Killer T Squad Leader.
  Killer T Squad Leader: "Hey!! Untie us first before you strike a pose!!"
• Berserk Button: Seeing a picture of herself in a maid outfit from her childhood is enough to reinvigorate her from stress, sending her into a rage against anyone who might have seen the photo.
• Blush Sticker: Has this right after defeating Cancer Cell, as result of her laugh.
• Bomb Whistle: Right before she lands on Killer T Squad Leader.
• Chuunibyou: Implied to be one based on photos of her youth and while off-duty.
• Cross-Popping Veins: Put her and Killer T Squad Leader together, and this will happen quite often.
• Curb-Stomp Battle: Once she is properly activated with laughter (after throwing Killer T Cell to B Cell's antibody gun, mocking him), she defeats Cancer Cell easily with one strike of her saber.
• Curtains Match the Windows: Has dark gray eyes and black hair.
• Deadpan Snarker: Her default state.
• Death Glare: Gives Killer T a terrifying one after he dumps a bucket of water on her head.
• Dissonant Laughter: During the duel with the cancer cell, NK activates herself by laughing.
• Elegant Gothic Lolita: Dresses like one as a Cell School student.
• Fire-Forged Friends: With Killer T Cell Squad Leader and Neutrophil during the Cancer arcs.
• Gray Rain of Depression: Has her own cloud when she has trouble killing an antigen-shifted influenza virus.
• Hand Gagging: Gives a rather forceful one to Neutrophil and Killer T Squad Leader at the same time, with her elbow and hand respectively.
• Headbutting Heroes: This with Killer T Cell. Based on their shared origins as NK/T Progenitors, this could also be construed as Sibling Rivalry.
• High-Pressure Emotion: When Dendritic Cell exposes embarrassing images from her youth, NK goes completely red. Same when Neutrophil catches her bemoaning about the aforementioned event.
• Jerk with a Heart of Gold: Is cold, aloof and rude to her allies, and belittles Ordinary Cells. However, she cares about the well-being of the body, is genuinely shocked and worried about her allies when they get injured, and even tolerates the presence of the Lactic Acid Bacterium and helps it find its way back home.
• Just Toying with Them: Immediately sees through Cancer Cell's disguise, and plays along with him so that she can fight him one on one.
  NK Cell: "I worked really hard to keep from laughing at your little act! You gotta try harder to make it worth my ti-"
• Laser Blade: NK's saber becomes this after she gets activated by Dendritic Cell.
• Luminescent Blush: Sports this when she is laughing.
• Machete Mayhem: NK's way of dispatching cells with her saber, essentially.
• Motive Rant: NK, tired of hearing Ordinary Cell's complaints about why immune cells must kill bacteria, delivers a rant to him and goes so far as to state that all the other cells would be long dead if immune cells weren't around. This speech shocks even Neutrophil, who chides NK.
• Noblewoman's Laugh: Gives Killer T Cell Squad Leader an "Ohohoho" while dragging away Cancer Cell.
• Not Quite Dead: During the Cancer cell fight, NK is seen going motionless and seemingly dies under some rubble. She's just resting though.
• Old Shame: In-Universe. According to NK's reaction herself, she's implied to be a macrophage fangirl.
• One-Man Army: NK has a habit of working alone, brushing off (sometimes forcefully) assistance from other immune cells. Holds her own fairly well against foreign organisms and cancer cells. This is because she doesn't want other immune cells going up against something out of their league and ending up in harm's way.
• Power Glows: Has one when activated by laughter.
• Prescience by Analysis: NK herself explains that this is how she's so effective against Bacterium and Cancer Cells. This is seen a bit in the intro to the anime where NK casually slashes at bacteria, sometimes without even looking at them.
• Sitcom Archnemesis: Has this dynamic with Killer-T Cell despite being Immune Cells. She usually goes out of her way to make his life miserable even in the face of danger. Although when faced with a tough enemy they can have an unspoken truce to defeat said enemy.
• Slasher Smile: She makes a rather scary one in chapter 22 when she sees a photo of her past in a cell school uniform (thrown by Dendritic Cell), threatening to kill anyone who has seen the photo.
• Surrounded by Idiots: NK thinks this internally, when dealing with Neutrophil, Killer T Squad Leader and Ordinary Cell. Neutrophil even points out to Ordinary Cell that NK is especially sharp.
  NK Cell: "They're morons, all of them."
• Tank-Top Tomboy: She wears a black tank top and shorts, fitting for a tomboyish Action Girl.
• Tomboy: Dresses and acts boyishly.
• Tomboy and Girly Girl: She's the tomboy to the Macrophage's girly girl. Unusually for this trope, Macrophages may be the only cells that rival her in badassery.
• Tomboy with a Girly Streak: If her past is anything to go by, she enjoyed wearing feminine clothes, like lolita outfits.
• Trauma Button: The shock of seeing a photo of her younger self in a Cell School uniform causes her to attack her own allies, break her weapon, eat the aforementioned photo, and turn into a broken record.
  Neutrophil: N-NK, what happened...?
  B-Cell: You cracked your precious saber...
  NK Cell: *eats photo* I'll kill anyone who saw it... I'll kill anyone who saw it...
• True Sight: Of a sort. In contrast to T Cells, NK Cells do not need antigen presentation and just kill cells (or rather, order them to) if they sense that the cell isn't displaying the MHC-1 protein, which is also where they get their name from. This is neatly represented in the anime by T Cell not being able to see through Cancer Cell's disguise, but NK Cell being primed to confront him as she had already sensed something off about him (i.e him not displaying the aforementioned protein in real life).
• Unsportsmanlike Gloating: Tricks Killer-T into running into B-Cell's antibody fire, and laughs for a full three panels. Somewhat justified, as laughter activates her, allowing her to finish off the cancer cell.
• Volleying Insults: Hand slipping and senility with Killer T Squad Leader.
  NK Cell: Oops! My hand slipped!
  Killer T Squad Leader: My bad, my foot slipped!
  NK Cell: Sorry! My elbow slipped!
  Killer T Squad Leader: That's too much slipping! You going senile or what?
  NK Cell: You're one to talk!
  Killer T Squad Leader: I'm gonna kill you!
  NK Cell: Huh! I'd like to see you try it!
• Two Guys and a Girl: With Neutrophil and Killer T Squad Leader. Acts as a foil to Killer T.
• Worf Had the Flu: She was unable to kill a new strain of Influenza Virus cause of stress. An old photo from Dendritic Cell snapped her out of it.

Memory B Cell

Voiced by: Yūichi Nakamura (Japanese), David Vincent (English)

A Memory B Cell. Often referred to as Memory Cell, or simply Memory.

---

• Absent-Minded Professor: Ironically is this, despite having Memory in his name. Consults notes often and forgets or has a delayed reaction regarding immunization and identification.
• Chuunibyou: Of the "Desperately trying to convince everyone they're a wizard" variety during the "Aquired Immunity" chapter. While his dream about Mumps makes him *think* he's a prophet, it comes across as a kid trying to open a supposedly-uncooperative (read: entirely nonexistant) Third Eye.
• Comical Overreacting: His reaction to almost any and all occurrences in the body.
• Failed Attempt at Drama: He dramatically drops an ominous-sounding prophecy to White Blood Cell...before realizing that he forgot it, so he has to run back and get his notes before reattempting the dramatic announcement. White Blood Cell humors him.
• Head Desk: Starts banging his head against the wall in Episode 12, when he realizes he can't remember a thing. Does this to the point of actual bodily injury.
• Ironic Name: Is called Memory B Cell, but in his own words, he "can't remember a thing".
• Nervous Wreck: The presence of Cedar Allergens is enough to make him Freak Out. He even continues spouting nonsensical prophesies even if it looks like B-Cell took care of the mess. He does, however, have good reason to be that way, since everything he described came to pass.
• Properly Paranoid: Initially, he looks like a deranged weirdo spouting words without any sense about some apocalyptic prophecy recorded by the previous Memory Cells. His worry ends up being right when the things he says turn out to be a prediction of the allergic reaction, that causes lots of destruction.
• Prophecies Are Always Right: All the pieces of information that he remembers and predicts always end up happening. Justified, since the "prophecies" he has are actually reactions of the body or medical processes that happen regularly in the body and that were recorded by previous Memory Cells before him.
• Seers: Apparently, he obtains the ability to predict the future in chapter 13, as he has a prophetic dream involving a meteor shower, cells fighting each other and a messenger from the outside world. Subverted later in the chapter when it's revealed it's actually a memory from a vaccination against the mumps virus that happened long ago (the messenger from the outside being the vaccine, the meteor shower being the capsules where the weakened mumps-infected cells are contained, and the cells fighting each other being the cells of the immune system defeating the weakened viruses easily).
• The Smart Guy: Is expected to remember viruses and their counters, and is often seen reading books. His workstation is filled with articles and publications.
• Those Two Guys: With B Cell. Justified, as his memories of antigens are required to create the antibodies that B Cell shoots. Both of them share the same workspace, and apparently (based on Dendritic Cell's photos), they were roommates in cell school.
• Torches and Pitchforks: On the receiving end of a very downplayed example by the Ordinary Cells at the end of chapter 13, after B Cell reveals that the reason why the white blood cells went through so much troubles against an enemy that they should had defeated easily is because he was so centered in predicting his vision that he wasted time to reveal that they already had antibody information to deal with the mumps.

B Cell

Voiced by: Shoya Chiba (Japanese), Erik Kimerer (English)

A B Cell^note given his function, he is most probably a plasma cell.. An energetic young man responsible for employing antibodies against foreign substances.

---

• Ammunition Backpack: His antigens are depicted as chem sprayers, complete with a tank of fluid on his back.
• BFG: His main weapon. It shoots antibodies. Interestingly enough, he seems to be the only cell who possesses a firearm of any sort.
• Captain Oblivious: B-Cell once cheerfully talked about how Memory Cell screwed up his job, resulting in a hard fight against the mumps virus, right after they conquered the invasion. In front of the exhausted normal and immune cells. With Memory Cell nearby... Cue mob chase.
• Grease Monkey: B Cell dresses like one and is generally good-natured. He's also strong enough to wield the various Antibody devices. He can be seen tinkering with his gear at his workstation and uses a different gun every time he appears.
• Interservice Rivalry: With Mast Cell. Both blame each other for the allergic reactions after doing their respective jobs.
• Let Me at Him!: In anime, he's ready to fight Mast Cell about her histamine overload, especially since he was initially blamed for the allergy disaster.
• Little Useless Gun: He attempts to kill an Antigen-Shifted Influenza virus with a handgun version of his antibody gun, which does absolutely no damage to the virus.
• Luminescent Blush: He has this after being embarrassed by Dendritic Cell.
• Macross Missile Massacre: He apparently has the ability to release many missiles out of his backpack when he's activated, as shown in chapter 22.
• Making a Splash: His antibodies are portrayed as water, making his BFG some kind of water gun.
• Screw This, I'm Outta Here: As soon as the influenza evolves to influenza A and realizes his antibodies don't cause any harm to it, he leaves the battlefield with the excuse that he needs to develop new antibodies. Be it justified or not, his allies don't buy his reason.
• Short Range Guy, Long Range Guy: He's the long ranged BFG wielder to the rest of the short range immune cells who fight up close with blades or fists.
• Those Two Guys: With Memory Cell. Justified, as B Cell's ability to fight relies entirely upon Memory Cell's records of antigens in order to create antibodies to shoot. Both of them share the same workspace, and apparently (based on Dendritic Cell's photos) were roommates in cell school.
• Torches and Pitchforks: On the receiving end, after it's believed he caused the allergic reactions.
• Unfriendly Fire: Accidentally shoots Killer T during the cancer arc. In his defense, NK had misled Killer T to run in the direction of B Cell's fire.
• Volleying Insults: With Mast Cell. The scene is expanded in the anime:
  B-Cell: Overproduction of histamines did the damage but nice try!
  Mast Cell: I did my job exactly how the manual said to!
  B-Cell: Well, then you must have read the manual wrong! Don't you know how to do your job without taking direction, Fatty Fat Cell?
  Mast Cell: I can't believe you'd call me that! Especially when the "B" in "B Cell" stands for "bonehead" ^note  A Woolseyism of Baka !
  B-Cell: What did you just say!?
  Mast Cell: I called you a bonehead, bonehead!
  B-Cell: Well, bring it on, then, you fatty!
• Worf Had the Flu: Gets overran by cells infected with the mumps virus due to needing to have the antigen presented first (something he explicitly says) ^note  This is equivalent to not having ammunition to shoot with . When Memory B cell gets better, he gets rid of them easily.
• You Are Fat: Calls Mast Cell a "Fatty Fat Cell" much to her chagrin.

Mast Cell

Voiced by: Ayako Kawasumi (Japanese), Maureen Price (English)

A Mast Cell. She plays an important role in the allergic response.

---

• Destructive Saviour:
  • She ends up producing too much histamine after being confused by the elevated number of IgE that B Cell released previously. This does take out most of the Cedar Allergens, at the cost of causing an allergic reaction (that, in the scale of the setting, has apocalyptic results). Justified due this being a Foregone Conclusion, since that is the usual response to allergies, something that U-1146 lampshades.
  • It seems her actions tend to cause mayhem more often than not, thing that garners her the animosity of Ordinary Cells, who tend to be victims of the histamine she releases.
• Heroic BSoD: Has a small one in chapter 16 after the complaints she receives from Ordinary Cells makes her to have doubts of her actions. Thankfully, she snaps out of it thanks to Basophil's speech.
• I Am Big Boned: Takes serious offense to getting called "Fat Cell" by B-Cell.
• Interservice Rivalry: With B-Cell. Both blame each other for the allergic reactions after doing their respective jobs.
• I Resemble That Remark!: After Mast Cell starts releasing large amounts of Histamine in response to a minor threat, some cells come into her office to complain about her hysterical nature. Mast Cell responds by throwing a violent temper tantrum.
• Never My Fault: Played for Laughs at the end of chapter 16. Just when she is about to apologize to the Ordinary Cells for the daily troubles she causes during her job, she angrily tells them that she didn't do anything wrong after rethinking the situation. Once again, an argument between her and the Ordinary Cells happens.
• Nightmare Face: Pulls a terrifying one when a Ordinary Cell calls her hysterical in chapter 16.
• Non-Indicative Name: Also known as "fat cells," though they have nothing to do with fat.^note The Germans who first discovered this cell called them "Mastzellen," or "fattening cells" since they were first thought to be a nutrient transporter, but when brought to Japan, it was translated to Himan Saibou, or "fattened cell." Calling her this is a major Berserk Button for her.
• Office Lady: Her workplace is apparently an office. It is implied that she lives (or at least sleeps) in there too.
• Rousing Speech: She gives herself one when she carries out procedure.
• Stealth Pun: Mast Cell is extremely busty, referencing mastos, the Greek word for breast (the name actually comes from the German word for fattening, as it was once believed Mast Cells provided nutrients to other cells).
• Throw the Book at Them: Starts hitting B-Cell with her manual when he goes too far in his insults.
• Torches and Pitchforks: On the receiving end, after it's believed she caused the allergic reactions.
• Volleying Insults: With B-Cell. The scene is expanded in the anime:
  B-Cell: Overproduction of histamines did the damage but nice try!
  Mast Cell: I did my job exactly how the manual said to!
  B-Cell: Well, then you must have read the manual wrong! Don't you know how to do your job without taking direction, Fatty Fat Cell?
  Mast Cell: I can't believe you'd call me that! Especially when the "B" in "B Cell" stands for "bonehead"!
  B-Cell: What did you just say!?
  Mast Cell: I called you a bonehead, bonehead!
  B-Cell: Well, bring it on, then, you fatty!

(Former) Naive T Cell / Effector T Cell

Pre-activation.

Post-activation.

Voiced by: Mutsumi Tamura (as Naive T Cell), Kenji Nomura (as Effector T Cell) (Japanese), Laura Stahl (as Naive T Cell), Chris Tergliafera (as Effector T Cell) (English)

A Naive T Cell, later an Effector T Cell. Referred to as Naive.

---

• Anime Hair: As Naive T Cell, he has a blond forelock of hair that's just barely visible under his hat, but as Effector T Cell it grows significantly and sticks straight up.
• Big Ol' Eyebrows: As Effector T Cell, his eyebrows are a lot bigger.
• Brought Down to Normal: Played for Laughs at the end of the third episode of the anime, where he reverts to Naive T Cell after being defeated by the Ordinary Cell infected of influenza A in one punch. Doesn't seems to stick for much, however, as he is portrayed as Effector T Cell in his following appearances.
• Call-Back: During the chapter featuring the Rhinovirus, this guy clearly shows up as Effector T Cell and stands out from the other Killer T Cells. He makes more appearances in the Thymocyte and Second Cancer stage arc, too.
• The Cavalry: He returns to the battlefield after being activated, to turn the tide of the battle against the Influenza.
• Expy: Effector T Cell is a pretty obvious one to the various protagonists of JoJo's Bizarre Adventure, from his overall design, his over the top manliness, use of Megaton Punches, and chanting "ORA ORA ORA" when attacking.
• Me's a Crowd: After becoming activated, he undergoes cell division.
• Muscles Are Meaningful: Sported very big Jojo-like muscles after activating to an Effector-T Cell. And it is the real deal, as his presence is the key of fighting the Influenza Virus (though B-Cell did half of the work too).
• Never Bring a Knife to a Fist Fight: Used a tiny little knife as his weapons before taking his level in badass. After that, all he needs are his guns.
• Not So Above It All: Gladly plays badminton with the Ordinary Cell who lives right next to the T Cell base in the Pharynx.
• One-Man Army: Becomes this after being motivated by Dendritic Cell and gaining confidence in himself. Additionally, the fact that he duplicated himself after turning into Effector T-cell would technically make him this two-fold, with him ending up being an army of armies, even if only temporarily.
• Sleeves Are for Wimps: After evolving into Effector T Cell, his already-short sleeves are torn off at the shoulders.
• Took a Level in Badass: A very spectacular example. Thanks to the motivation Dendritic Cell gives to him, he goes from a wimpy weakling to a mountain of muscles straight out of JoJo's Bizarre Adventure or Fist of the North Star who destroys his enemies by punching them!
• Well-Trained, but Inexperienced: Even after implicitly surviving harsh training in the thymus, Naive T Cell screams in terror and runs when an influenza virus comes. After a pep talk by Dendritic Cell, he becomes Effector T Cell and returns to take out the virus.
• The Worf Effect: While he easily wipes out the Influenza B virus, a single Influenza A sends him flying with a slap, causing him to revert to Naive and showing off how much more powerful the evolved virus is.

Dendritic Cell

Voiced by: Nobuhiko Okamoto (Japanese), Griffin Burns (English)

A Dendritic Cell, whose job is to notify other immune system cells of bacterial invasions and viral infections, as well as to provide Power Ups to T Cells.

---

• Agent Peacock: Sports a disco-like police outfit when he is activated by the Lactic Acid Bacterium.
• Alcohol Hic: In the Cytokines chapter, the polysaccharides made for Dendritic Cell by the Lactic Acid Bacteria is depicted as alcohol, and when activated, he wobbles and hiccups.
• Astonishingly Appropriate Appearance: He wears a green uniform, works out of a tree, and has a small plant sticking out of the side of his hat. Dendritic cells get their name from the branch-like dendrites (not the same as the ones produced by neurons) they generate.
• Blackmail: This is one of the ways he gives a Power-Up to other immune cells—by showing Embarrassing Old Photos of them that would make the cells shiver even when the act was done many millimetres away. This is used to represent the action of cytokines.
• Communications Officer: Transfers information from Macrophages to Helper T Cell, as seen in Episode 3.
• Cool Shades: Sports a pair when he's activated by the polysaccharides of one of the lactic acid bacteria. Along with a BDSM whip, for some reason...
• Embarrassing Old Photo: Dendritic Cell weaponizes these as part of his role in the immune system (as well as for his own amusement). Cytokines are represented as very embarrassing photos that activate the Immune Cell who sees them into destroying stronger enemies. He has thousands of said pictures in his collection.
• The Gadfly: Absolutely loves messing with the other immune cells by revealing photos of their often embarrassing youth.
• Knowledge Broker: Has information on most other cells. Some of that information is probably best left unread.
• Long-Lived: The Dendritic Cell is depicted as looking the same age he does in the present in the flashback to Helper and Killer T's childhood. And he clearly knows more than the other immune cells would want him to know.
• Nice Guy: In general, he's very friendly, polite, and kind to his comrades. In particular, he delivers a heartwarming speech to a sobbing Naive T-Cell, allowing him to activate into an Effector T-Cell.
• Power-Up: One of his primary functions is providing these to the various immune cells. Sometimes he can do it as encouragement, other times it's downright blackmail!
• Psychotic Smirk: Sports a very creepy one, while asking a favour to one of the lactic acid bacteria. The favour is for the bacterium to produce polysaccharides to activate him and help the other cells against the new influenza.
• Rousing Speech: He's capable of encouraging Naive T Cells using these, awakening their killer instinct.
• Say It with Hearts: His dialogue ends with hearts when he's activating (blackmailing) the immune cells with embarrassing photos of them.
• Stronger Than They Look:
  • While he looks rather average, when he's activated, is strong enough to defeat an influenza-infected cell in one kick.
  • Even when not activated, he's nimble enough to dodge Killer T Cell and Helper T Cell coming after him. All the while wearing a dirty grin on his face.
• Troll: To almost sadistic degrees. He adores messing with other cells by showing embarrassing photos of their youth, and enjoys the mayhem his actions cause way too much.

Langerhans Cell

Voiced by: Motomu Kiyokawa (Japanese)

A sub-species of Dendritic cell.

---

• Brainwashed and Crazy: Undergoes this after picking up a mask left behind by a mosquito bite which attaches itself to his head.
• Cool Old Guy: He's kind to AE3803 in his introduction, and he attempted to prevent her from being sucked by the mosquito proboscis. He was out of reach, but it retracted before she could be taken.
• Evil Old Folks: Played with. They are all depicted as old men with fancy clothes and facial hair, and they serve as the antagonists in chapter 16, but the evil part is only due to brainwashing.
• Named After Somebody Famous: Langerhans cells were named after the scientist who identified them, Paul Langerhans. The caption/narration explaining this cell notes that it should not be confused with the islets of Langerhans, also named after the scientist but are pancreatic regions that have nothing to do with dendritic cells.
• Pokémon Speak: Langerhans Cell speaks normally, but he and the other infected cells can only say "deng" after being taken over by the dengue fever masks.
• We Hardly Knew Ye: The first Langerhans Cell we're acquainted with is killed in the same chapter he's introduced, due to being infected by the Dengue virus. However, they weren't all killed, since one Langerhans Cell who evaded the virus is shown at the end of the chapter.

White Blood Cell / Neutrophil Squad (U-2048, U-2626, U-4989, U-2001)

Voiced by: Kensuke Satou (U-2048), Junichi Yanagita (U-2626), Kentaro Kumagai (U-4989), Akinori Egoshi (U-2001) (Japanese), Christian La Monte (U-2048), Lucien Dodge (U-2626), Sean Chiplock (U-4989), Zachary T. Rice (U-2001) (English)

A quartet of recurring Neutrophils. They are identified by their hair styles, U-2048 having straight hair, with both eyes unobstructed; U-2626 having hair covering his eyes; U-4989 having uncombed hair, with both eyes unobstructed; and U-2001 having a buzz cut.

---

• Adorably Precocious Child: As myelocytes, they took to training very well, mobbing a large cloth training puppet with the rest of his squad.
• Bromance: U-4989 with U-1146. Close friend to aforementioned character, and is distraught when harm comes to U-1146.
  U-4989: Dummy! You big dummy!! I told you a million times not to mess around like that!! Seriously! I'm not gonna care anymore!! I'm not!!
  U-2626: Calm down, No. 4989!
• The Cavalry: To Ordinary Cell, when he was captured by opportunistic and harmful bacteria in the intestines.
• Childhood Friends: With U-1146 and Eosinophil. They were classmates in Cell School and were raised in the same Bone Marrow, and with the former, they patrol the same region as adult cells. There is also a picture of the four of them that was taken in a picture booth, complete with "BFFs" and sparkling eyes filters.
• Harmless Electrocution: Are electrocuted by Staph A's fibrin when she uses coagulase to incapacitate them. While severely wounded and dazed, they’re still alive by the end of the ordeal.
• Help, I'm Stuck!: Whilst transmigrating, they get stuck between a couple buildings, and need the other neutrophils to pull them out.
• Improvised Weapon: U-4989 is shown to use these Once an Episode. Some examples include a box of steamed buns, his knife tied to a pipe as a makeshift spear, and wearing acid-proof enamel cookware as armour. He also used branches as a (playing) weapon as a myelocyte.
• Funny Background Event: U-4989 has been seen doing some rather ridiculous things, such as washing up by jumping into the canal than using the faucets and buckets provided, only the top of his head, his cap, and ID tag visible. (In the anime, he is swimming in the canal.)
• Last Stand: In the Influenza arc, they get cornered into an alley by the swarm of Influenza infected cells. Fortunately, Effector T Cell comes to the rescue.
• Leeroy Jenkins: Played with. U-4989 nearly got sucked out of the body in Chapter 4/episode 2 because he didn't turn his L-Selectin on. He's shown to have survived later.
• The Medic: U-2626 can be seen all-throughout in Chapter 27 attempting to stem the severity of U-1146 and Eosinophil's wounds.
• Only Sane Man: U-2626 in Chapter 27: with U-4989 overreacting and U-1146 on his deathbed, it's down to him to play the straight man.
• The Reason You Suck: Along with U-1146, they taunt the campylobacter on their faults, before assaulting them.
• Shrug Take: U-2626 when he sees U-1146 and Eosinophil revived from their injuries via embarrassment.
• The Squad: Form a squad or patrol the same sector with U-1146.
• Tears of Joy: U-4989 is extremely moved to the point of tears when Red Blood Cell refers to White Blood Cells as being "super reliable".

White Blood Cell / Neutrophil (U-1110)

Voiced by: Satoshi Hino (Japanese), Xander Mobus (English)

An instructor Neutrophil. Is bald and almost always seen with a Pseudomonas puppet on his right arm.

---

• Badass Teacher: The one tasked of teaching the erythroblasts about the danger of the bacteria, and also capable of one-shotting a pseudomonas easily.
• The Cavalry: Arrives just in the nick of time to save U-1146 and AE3803 from the Pseudomonas.
• Master Actor: Convinces (and terrifies) an entire class of Erythroblasts that he's a bacteria, hell-bent on eating them. Also scares Eosinophilic Myelocyte.
• Mr. Exposition: Regarding the percentage of Basophils in the White Blood Cell population. (0.5%)
• Repeated Cue, Tardy Response: Misses Macrophage's cue and has to ask if he should start his performance.
• Veteran Instructor: Is no slouch when it comes to killing bacteria, and works in an instructional position at cell school.

Thymic Epithelial Cell

Voiced by: Rikiya Koyama (Japanese)

---

• Big Ol' Eyebrows: The first instructor shown has thick rectangular brows.
• Drill Sergeant Nasty: They're portrayed as very harsh drill instructors to the recruits.
  Welcome to hell, you useless runts! Listen up! The thymus is where we find out which of you we can use, and which ones we can't! We don't need blockheads that can't do their part when the time comes!
• Mr. Exposition: Largely responsible for explaining the development of thymocytes in the Thymocytes chapter/episode.
• Sweet Tooth: During the first round of drills, when the thymocytes are still kids, the main instructor is munching on a cookie while lecturing the recruits.

M-Cell

Voiced by: Sho Hayami (Japanese)

A microfold cell, referred to as M Cell. He lures bacteria into Peyer Patches.

---

• The Bartender: He runs a Peyer's Patch which seems like a bar for the body's cells but easily turns into a deathtrap for bacteria. He also dresses like a bartender in an upscale establishment.
• Devil in Disguise: To any bacteria that stumble into his Peyer's Patch.
  M Cell: Please. Enjoy your meal. It is... your last supper, after all... eat to your hearts' content... Heh heh...
• Eyes Always Shut: His eyes are always closed, giving him a serene appearance.
• Inescapable Ambush: Literally his main function. Managed to lure four bacteria into a room containing no less than: 18 B-Cells, seven Killer T Cells, five Neutrophils, five Dendritic Cells and one Macrophage.
• My Card: While he introduces himself, he presents a fancy-looking business card with his name and function.

Circulatory System

Platelets

Leader-chan voiced by: Maria Naganawa (Japanese), Xanthe Huynh (English)
Backwards Cap-kun voiced by: Manaka Iwami (Japanese), Jackie Lastra (English)

Platelet cells, who act as a construction and repair crew whenever the body is injured. Typically refers to the platelet with long brown hair seen in the photo, "Leader-chan."

---

• Adorably Precocious Child: Despite looking much younger than other cells, they're still hard workers who are devoted to their jobs, even if being small can get in the way of their work sometimes.
• Badass Adorable: They're ridiculously strong for their size and have no problem putting themselves in danger to get their job done. They're also downright adorable and elicit Cuteness Proximity reactions in everyone.
• Badass Pacifist: Even though they don't engage in combat themselves, they still march to the front lines of danger to complete their job of sealing up wounds, which can completely turn the tides of a battle and secure victory for the immune cells.
• Big Brother Worship: They all look up to and respect the older big brother and sister cells like Red Blood Cell and White Blood Cell.
• Breakout Character: Despite starting as supporting characters, their popularity kept leading to them being granted more focus. These days Leader-chan is basically the Series Mascot and heavily used in promoting the series. She and the rest of the Platelet team would eventually receive their own spinoff series, Cells at Work: Platelets!
• Catchphrase: "Anone anone"^note "You see, you see,...", "Thank you for your hard work!", and "Heave-ho!"
• Chain of People: Does this to an extreme when they rescue one of their fellow platelets. They're so in sync about this that they form the bridge as they're falling. Truly a testament to the amount of team synergy that these little cells have.
• Cheerful Child: The whole lot of them are just so positive and cute, they invoke Cuteness Proximity in any cells that interact with them (even the normally hard-as-nails killer T Cells!)
• Children Are Innocent: They are kind and polite to everyone, with all the other cells being hit with Cuteness Proximity at the sight of them and happy to play with them.
• Curtains Match the Windows: Leader-chan has brown eyes to match her brown hair.
• Cuteness Proximity: Their very presence induces this reaction in everyone, in-universe and out.
• The Cutie: Their arrival always lightens up the mood and leads way to a whole heaps of cutesy and adorable moments.
• A Day in the Limelight: The Platelets, especially Backwards-Cap-Kun, are the focus of chapter 26.
• Fun Personified: Aside from their role of sealing up wounds and construction, the Platelets are the primary source of the cute and fluffy moments in the show.
• Improbable Infant Survival: No Platelets are seen getting hurt or dying during the hemorrhagic shock in Episode 11-12.
• Leaning on the Fourth Wall: The scrape chapter and episode end with her describing a scab.
• Leitmotif: "March of the Platelets," a cute and upbeat marching theme punctuated by whistles and xylophone.
• Ms. Fixit: One part of their job is to repair structural damages by creating thrombus.
• Muscles Are Meaningless: Despite having the bodies of children, they are strong enough to drag around several other cells to turn them into scabs.
• Nerves of Steel: No matter what situation occurs that would require their assistance, nothing is capable of discouraging them from doing their jobs, with dangerous bacteria barely getting a reaction from them (since they know the Neutrophils will keep them safe) and the situation involving the hemorrhagic shock injury only resulting in them being even more determined than usual to get the job done.
• Nice Guy: Not just the Platelet Leader, but all the Platelets are unfailingly kind and polite towards each other and all other body cells. Even enforced to a degree in chapter 4/episode 2. While giving instructions to the Platelets during a blood clot, the Leader clearly states "No fighting with other kids!"
• Not So Above It All: Downplayed. The Platelets are often seen as being unflinchingly kind and polite, but when gold medals are involved, their effectiveness increases tenfold in hopes of earning it but at the cost of their characteristic politeness; One of them even steps on U-1146 in their gold medal bliss.
• Only Known by Their Nickname: Instead of alphanumerical designations, Platelets are identified individually by some unique feature or position, such as the female "Leader-chan" and "Backwards-Cap-Chan."
• Series Mascot: The Platelets, especially Leader-chan, are featured heavily in promotional material and the opening/ending credits despite being supporting characters at best.
• Spotlight-Stealing Squad: Leader-chan is the one who gets nearly all the focus and all the dialogue. Backwards-Cap-Kun is the next most focused Platelet and often accompanying Leader-chan.
• Sticky Situation: Much to the consternation of the red blood cells, the Platelets happily ensnare them in fibrin nets and gather them into one massive and uncomfortable blood clot.
• Token Mini-Moe: They are the only kind of working cells depicted as little boys and girls. Justified, as real-life platelets are smaller than other cells.
• Wise Beyond Their Years: Despite being small children, they do their jobs with all the efficiency and maturity of adult cells. Even in the face of a devastating hemorrhagic shock injury, they don't hesitate to get straight to work repairing the wound.
  • This is justified, as Platelets have rather short lifespans when compared to other cells. So having the maturity of an adult is a necessary factor for them to perform their jobs efficiently.

Senpai Red Blood Cell (AA5100)

As an Erythroblast.

Voiced by: Aya Endo (Japanese), Kira Buckland (English)

Another Red Blood Cell, often called Senpai or AA5100.

---

• Affectionate Gesture to the Head: Pinches AE3803's cheeks playfully when she finally manages to circulate the body without getting lost. Comments that she does so cause her cheeks are soft.
• Airplane Arms: Runs like this (quite happily) to the neck and armpit areas when the body receives an intravenous rejuvenation.
• Ascended Extra: Still a supporting character, but shows up more frequently in the anime than the manga.
• Bystander Syndrome: She is shown to be annoyed by Red Blood Cell's aversion of this trope and her constantly getting involved with White Blood Cell's shenanigans.
• Catchphrase: "Sure is peaceful, isn't it Senpai?" "Sure is." Usually right before something really bad happens.
• Cool Big Sis: Viewed as this by Red Blood Cell, as she constantly looks out for her and helps her with deliveries when needed.
• Cross-Popping Veins: Has a couple when she scolds AE3803.
• Fantastic Racism: Present at the beginning of the series, when she comments that White Blood Cells are creepy, despite having been saved by one just moments before. Subverted towards the end of the series as she becomes more accustomed to them.
• Let's Get Out of Here: Says this word for word when she encounters the influenza-infected cells.
• Meido: As with her fellow Red Blood Cells, it is implied that she wore a Meido uniform as a child, up until she graduated from cell school.
• Meaningful Name: Her name AA5100 is a hexadecimal color for a shade of brown.
• The Scream: Does this when she encounters cancer cells consuming nutrients.
• Sparkling Stream of Tears: Has this when reuniting with AE3803 after the hemorrhagic shock incident.
• Thousand-Yard Stare: Sports this after being on the bottom of the dogpile consisting of AE3803, Neutrophil and Memory B Cell.
• We Are Not Going Through That Again: Threatens to stop delivering with AE3803 if she keeps insisting on sticking her neck into other people's business. This scolding becomes a catalyst for AE3803 to become more self-sufficient.
  Senpai RBC: You! Still a newbie and you go sticking your neck in other people's business!^note Referring to AE3803's calling other Immune Cells for help during the first Cancer Cell arc You do that next time and I'll never deliver with you again!
  Red Blood Cell: I'm sorry... I just wanted to do something to help... I thought I did a good job...

Kouhai Red Blood Cell (NT4201)

Voiced by: Yui Ishikawa (Japanese), Jeannie Tirado (English)

Another Red Blood Cell. Often called Kouhai.

---

• Badass Boast: Claims that she's one of the most talented Red Blood Cells, and states that she's sure of it.
• Being Personal Isn't Professional: She's very direct, deadpan and prefers to get things done. Brushes off Red Blood Cell's attempt to socialize and teach her.
• Break the Haughty: Kouhai RBC is humbled after seeing Red Blood Cell continue to strive on to deliver packages, despite all seemingly being lost, going so far as to state that it taught her a lot about the dedication required to do the job well.
• Fantastic Racism: Like many others of her kind, she exhibits bigotry towards White Blood Cells, especially neutrophils, seeing them as little more than violent thugs who go overboard in their duties. As such, she is genuinely bewildered that Red Blood Cell is acquainted with and on good terms with so many of them.
• Insufferable Genius: Kouhai RBC is very good at her job, to the point where she needs minimal guidance. However, she is cold towards her superior and condescends Red Blood Cell when she feels their situation is futile.
• Not So Stoic: Despite being a major case of The Stoic, the hemorragic shock pretty much shatters her composure.
• Red Oni, Blue Oni: She is the blue to her more excitable and absent-minded sempai.
• The Stoic: In contrast to AE3803, she is extremely serious and professional, prioritizing the job above all else and not getting caught up in AE3803's antics or fooling around.

Transfused Red Blood Cell (DB5963)

Voiced by: Takayuki Kondō

The leader of a group of transfused erythrocytes.

---

• Big Damn Heroes: Appears right in the nick of time along with his fellow transfused blood cells, saving everyone and bringing the body back into working order.
• Big Ol' Eyebrows: Sports a pair of these. Easily a defining unique characteristic.
• Human Popsicle: The transfused Red Blood Cells turn out to be this, referencing blood centrifugation. One recalls that they were sucked up, frozen in their new home, then woke up in the current body with no recollection of where they were.
• Iconic Outfit: Unlike the cells in his new host body, this Red Blood Cell has a folded-down collar on his jacket, as well as velcro rather than laces on his shoes.
• Mr. Exposition: Shares his experience to Red Blood Cell and Neutrophil about being drawn from his host body, stored, and transfused into the current body.
• Rousing Speech: Gives his fellow transfused blood cells one after they realize that the body they're in is dying from severe blood loss, motivating them to help distribute oxygen/nutrients and bring the body back to full function.
  Transfused Blood Cell: "Long story short, that's how it is. They say no journey is too hard without good company... Well we gotta band together when times are tough! Well here we are now! We're Red Blood Cells-might as well go with the flow. We might be from different bodies, but our jobs are the same. Let's all work together... and carry this here oxygen! Yeah!"
  Assembled Blood Cells: "RAAAAAAAH!"
• Trapped in Another World: As a transfused cell, this is basically his experience. A mysterious force pulled him out of his homeworld, weird stuff happened, and then he woke up in a different world entirely. He even arrived just in time to help the locals save their world.
• Twinkle Smile: After explaining how he and his fellow blood cells made it into the body, he gives a smile that makes the background sparkle.

Megakaryocyte

Voiced by: Yuko Kaida (Japanese), Amber Lee Connors (English)

The progenitor of the Platelets, their mentor, and caretaker. Though her methods may seem very harsh, she loves her "students" very much and won't hesitate to lavish them with praise and rewards when they get their jobs done, and done well.

---

• Badass and Baby: She's always carrying a baby platelet strapped to her in a sling wherever she goes.
• Drill Sergeant Nasty: She's a very tough mentor to her platelets. In her first appearance, she's unsatisfied with their performance, calling it "careless" as she berates them.
• Jerk with a Heart of Gold: Megakaryocyte loudly belittles her platelets and enjoys coming up with insults for them. She also promises the best platelet a gold medal (called a bribe by the Neutrophils) to get them to complete a difficult task: mending an internal hemorrhage. However, she's very proud of them when the platelets finish the task with no losses and minimal damage to the body, and she decides that they all deserve medals for their work.
• Scary Teeth: Her teeth are all drawn as sharp. In the anime they're drawn as normal most of the time.
• So Proud of You: She is moved to tears when the platelets work together to mend a hemorrhage, and she says that she's glad that Backward-Cap Platelet finally matured and was able to be helpful.
• Statuesque Stunner: She's a very large and imposing cell. This somewhat reflects the fact that megakaryocytes are partially named for their size.
• Tears of Joy: Seeing her platelets working together moves her greatly.
• Tough Love: She's the progenitor and caretaker of the platelets and is very harsh on them, ready to berate them whenever she can, but she also recognizes a job well done.

Other Body Systems

Ordinary Cell

Voiced by: Yūsuke Kobayashi (Japanese), Bryce Papenbrook (English)

A typical body cell, depicted in the latter half of the manga. He lives right next to a T Cell base in the Pharynx. Called Cell Boy by U-1146.

---

• A Day in the Limelight: Is the focus character of Chapter 11.
• Ascended Extra: After his previous stint in Chapter 11, he becomes this in Volume 5 (Chapters 20-25), particularly in the Lactic Acid Bacteria arc, and effectively takes Red Blood Cell's place as The Watson and Supporting Protagonist.
• Character Development: Ironically receives this the most of all cells featured, despite his function being monotonous and never changing. He learns more about the realities of how the body and the various cells in it work, and learns to accept and appreciate both his own role and that of the other cells.
• The Generic Guy: All Ordinary Cells' character designs are meant to look as generic as possible. As if to drive the point home, their entire wardrobe consists of a white T-shirt simply saying "Cell" on it, jeans, and very generic sneakers.
• I Just Want to Be Special: Ordinary Cell feels like the lives of the Ordinary Cells are boring, compared to the works of the immune cells. In his words, he just wants to help someone and be thanked sincerely.
• Limited Wardrobe: The only thing they wear is a white T-short with the word "Cell" on it. Justified as these T-shirts represents the major histocompatibility complex, the mark for T-cells to identify whether the cell comes from the host.
• Supporting Protagonist: Serves as this to White Blood Cell in Volume 5 (Chapters 20-25), taking Red Blood Cell's place in this capacity.

Secretion Gland Captain

In Rain Dance outfit

Voiced by: Akinori Egoshi (Japanese), D.C. Douglas (English)

The leader of the Secretion Gland, usually shows up in episodes where secretion is involved (Influenza, Cedar Pollen, Heat Stress). Referred to by his subordinates as, Captain.

---

• Crazy Enough to Work: The idea of doing a rain dance is crazy and absurd in its own right, but when an intravenous rejuvenation happens shortly afterwards, even the narrator wonders if it was due to the Secretion Gland Captain's rain dance itself.
• Despair Event Horizon: He has his own when he realizes that there's nothing more the system can do to relieve the body of heat stress.
• Heroic BSoD: When he realizes his system can't do anything, he ends up donning a ceremonial outfit and begging the gods for rain.
• Manly Tears: When the body recovers from heat stress, he sheds several tears of joy.
• Rain Dance: He attempts one when the body is on the verge of death due to heat stress. His behavior breaks his subordinates out but ends up working when the body receives an Intravenous Rehydration.
• The Scream: The captain yells in panic when the Steroid shows up at his door.

Hematopoetic Stem Cell

The cells in charge of caring for other blood cells.

---

• Adaptational Nice Guy: In the anime, they appear less cynical and their comment that AE3803 would grow up to be a dummy is left out.
• Berserk Button: These cells get easily upset over the complicated naming of their fellow cells during their gestation. After all, they're the ones that have to process them.
• Bitch in Sheep's Clothing: Looks gentle and caring on the outside, but in reality, these cells are very jaded.
  Hematopoetic Stem Cell: (in the manga, about AE3803) She doesn't look like she can do any other work. I bet she'll grow up to be a dummy.
• People Farms: They work in a literal Baby Factory, supervising the production of infant Precursor Cells and assigning them to become different types of cell according to the needs of the body.

Intestinal Epithelial Cell

Cells found in the gastrointestinal tract. They are responsible for absorbing nutrients and water and are depicted as scuba divers in the story.

---

• Blush Sticker: When given an award for bravery.
• Hostage Situation: One cell was used as a hostage to force the Neutrophils to comply to their demands.
• Schmuck Bait: The Intestinal Epithelial Cell tells the Campylobacter holding him hostage that there is a weak spot in the intestinal mucus. It actually leads to a Peyer's patch, where the bacteria are dispatched by dozens of white blood cells.
• You Don't Look Like You: When we see him in the colon in Chapter 23, he has a facemask-style scuba helmet instead of separate goggles and air mask.

Goblet Cell

A mucous cell who lives in the digestive tract.

---

• One-Shot Character: Seen once near the middle of chapter 23 and never again.
• Powered Armor: Wears an Atmospheric Diving Suit instead of Scuba gear like his coworker, Intestinal Esophilial Cell.

Lactic Acid Bacteria

Voiced by: Rie Takahashi, Yuuri Yoshida, Yurika Kubo, and Natsumi Fujiwara (Japanese), Michelle Marie, Kayli Mills, Abby Trott, and Xanthe Huynh (English)

A blanket term for bacteria that produce lactic acid, which are classified as good bacteria. In this story they help in cleaning and maintaining gut and digestive organs along with fending off harmful bacteria.

---

• Badass Adorable: They're absolutely adorable little critters, but just one of these little guys can knock down a H. Pylori by itself when activated.
• Big Eater: One lactic acid bacterium alone can eat large amounts of purine.
• Cute Giant: A fully activated Lactic Acid Bacterium is utterly massive, around the size of Ordinary Cell's house, but it's still an utterly adorable critter that never loses its friendly and helpful personality.
• Friendly Enemy: The Neutrophils and other immune cells consider them allies and will not attack them even if they are classified as germs.
• Helpful Mook: Despite being germs, they don't do anything to harm the body, instead actually helping the cells in various ways, such as fighting off harmful gastric bacteria, aiding in the clearing away of rubble caused by bacterial attacks, and breaking down excess purine that gathers in the intestines by eating it.
• Pokémon Speak: Can only say nyuu, which comes from the Japanese term for lactic acid bacteria, Nyuusankin. They can even be heard saying it while singing along to the Season 2 anime opening.
• Rapid-Fire Fisticuffs: How one Lactic Acid Bacterium was able to defeat an H. Pylori.
• Ridiculously Cute Critter: They're incredibly tiny, able to have four of them fit snugly in the arms of one cell, and look like cute multicolored jellybeans with huge eyes and penguinlike flippers. Even when activated, unlike other germs that turn more monstrous, they simply grow a pair of small horns, with full activation only bloating them up to the size of houses. Regular Cell brings several home due to Cuteness Proximity and they play with yarn.
• Token Good Teammate: Unlike most bacteria, they're helpful and essential to the body.

Harmful / Invasive Cellular Organisms

Pneumococcus

Voiced by: Hiroyuki Yoshino (Japanese), Ben Diskin (English)

The series' first villain, a bacterium that causes pneumonia.

---

• Armor of Invincibility: His capsule serves as one, making it impossible for White Blood Cell to attack him directly.
• The Bus Came Back: One pnemococcus serves as a Starter Villain and gave Red Blood Cell a lot of trouble. Two more show up in Episode 8 but are quickly dispatched by White Blood Cell without Red even realizing their presence and they never get treated seriously this time round.
• Colour-Coded Characters: He is primarily purple. He's a gram positive bacterium.
• Combat Tentacles: Has many of them emerging from his head, back and hips.
• Hidden in Plain Sight: The crafty germ hides himself in Red Blood Cell's package and simply lets her deliver him to his destination.
• Inescapable Net: Uses his capsule as both this and a Smoke Bomb to throw White Blood Cell off his trail.
• Puzzle Boss: His capsule makes him immune to Neutrophil attacks. He would have been a Hopeless Boss Fight, but luckily for everyone but him, he winds up in the respiratory tract...
• Self-Duplication: U-1146 mentions that if left undisturbed to feed on nutrients, pnemococcus will start splitting into more of himself, eventually taking over and destroying the host.
• Sole Survivor: A horde of them appear at the beginning and are all quickly killed by the Neutrophils, but one survives and become the main antagonist of the episode.
• Starter Villain: The first menace presented in the series.
• Villain of the Week: One of them is the main villain of the first episode of the series and the first chapter of the manga. He is apparently the brother of another pneumococcus who attacks the body during the scratch incident, but this one acts as a minor antagonist.

Staphylococcus aureus

Voiced by: Mai Nakahara (Japanese), Cristina Vee (English)

A proud and haughty bacterium that causes staph infections.

---

• Beware My Stinger Tail: Her main weapon is a tail with a blade at the end of it.
• The Bus Came Back: A new group of them return to invade the body in Chapter 15.
• Colour-Coded Characters: She is primarily yellow, making honor to her second Meaningful Name.
• Cute Monster Girl: She has a graceful design and relies more on numbers and strategy than brute force, which gives her an air of sophistication, unlike the pneumococcus of the first episode.
• Didn't See That Coming: The reason why she fails both times in invading the body:
  • During the scratch incident, while her plan to deal with the white blood cells was good, she didn't predict the appearence of the Platelets. Once the scratch is successfully sealed and her fellow bacteria are killed, she doesn't last long against U-1146.
  • Once again, in chapter 15 she defeats the neutrophils in her fused form and thought she has already won, while forgetting about the monocytes/macrophages (to which her sister of the scratch episode took in account), who emerge from the blood stream in that moment. Once they appear, she is abandoned by her sisters and is quickly butchered by them.
• Dirty Coward: The remaining survivors of the group of Staphylococcus aureus of chapter 15 quickly abandon their leader once the macrophages appear.
• Flat "What": Her reaction when she finds out that the Neutrophils' "powerful reinforcements" are actually the adorable little Platelets!
• Fusion Dance: A group of them fuse together to evolve into a bigger and more powerful version of themselves. See King Mook below.
• God Save Us from the Queen!: Has an appearance with clear royal inspirations to her design, and is the leader of the bacteria swarm that seek to invade the scrape wound.
• Inescapable Net: Her main weapon in her fused state is a net made of fibrin called coagulase, used to trap and defend herself from neutrophils. It also can electrocute her victims.
• King Mook: Acts as this to the other germs and bacteria that invade in Episode 2/Chapter 4. In chapter 15, a group of them fuse together to form one of themselves. The fused version is much bigger and is able to produce and use coagulase, an enzyme that allows for extraction of fibrin (which is impenetrable by white blood cells) to be used as both a weapon and defense.
• Meaningful Name: Her genus means "grape cluster," due the clumps they form in small groups (both her "hair" and "dress" are grape-shaped). Her species means "golden," and she's properly presented as a yellow bacterium.
• Noblewoman's Laugh: Will occasionally raise a claw to her mouth and laugh haughtily.
• Ojou: Her design (including Ojou Ringlets) and mannerisms make her a clear Shout-Out to this.
• Recurring Boss: Is faced two times in the manga, one in chapter 4 (episode 2 of the anime), leading numerous bacteria that take advantage of the scratch to invade the body, and later in chapter 15, where a group of them appears intending to conquer the nasal cavity.
• Tertiary Sexual Characteristics: She sports prominent eyelashes, an indicator of her gender.
• Villain of the Week: Of the second episode of the anime and the 4th chapter of the manga, where she is the leader of a group of bacteria who take advantage of the scratch to enter and infect the body. The sisters of that S. aureus play this role in chapter 15, this time invading the nasal cavity.

Streptococcus pyogenes

Voiced by: Masaya Matsukaze (Japanese), Landon McDonald (English)

A very common red-colored bacterium that resides in the pharynx, the digestive organs and the skin. Produces many diseases.

---

• Animal Motif: His red coloration, huge sting whip with a blade at the end of it and his arms that ends in blades gives him the image of a scorpion.
• Beware My Stinger Tail: Not a tail, but has some kind of biological whip from the back of his head with a blade attached to it. He uses this to fight and to grab his victims.
• Blade Below the Shoulder: His arms ends in some kind of tiny blades.
• The Bus Came Back: Two of them appears again in chapter 10/episode 8 trying to ambush AE3803 during her travel through the circulatory system. They are easily defeated by U-1146 (who was watching over her).
• Colour-Coded Characters: He is primarily red.
• Curb-Stomp Battle: Both of their appearences ends with them being easily defeated by the neutrophils.
• Mook: One of them acts as this for Staphylococcus aureus during the scratch episode. He is quickly killed by U-4989 and U-2048 when he tried to attack the red blood cells along with a Pseudomonas.
• Spikes of Villainy: Possesses four spikes on his shoulders, and has lots more in his head-whip.

Cedar Allergen

Voiced by: Kazuyuki Okitsu (Japanese), Armen Taylor (English)

Large, slow-moving beings from cedar pollen. Unfortunately for all the cells involved, the body is very allergic to cedar pollen.

---

• Anti-Villain: As one doctor points out, they're just harmless male sex cells in a protective layer, trying to find female flowers to germinate. They're just looking in the wrong places.
• Monster of the Week: Of chapter 2 of the manga/episode 5 of the anime.
• Non-Malicious Monster: As U-1146 points out, unlike bacteria or viruses, they don't cause an illness by themselves. As it is shown, the problem is the immune system overreacting to their presence, which is what an allergy is.
• Not-So-Harmless Villain: Downplayed example. They initially appear innocuous and easy to kill, but once they multiply, they start to cause destruction. However, the biggest threat they present are not themselves, but rather what their presence makes the immune system do...
• Pokémon Speak: The only thing they are able to say is "Cedaaar".
• Sympathy for the Devil: White Blood Cell seems sympathetic towards them, citing that even though it was his job to destroy them, he at times still pitied them. In the anime, Red Blood Cell agrees, and both fold their hands in a Due to the Dead.

Steroid

Medicine taken to control allergic reactions. Appears as a robot destroying everything in sight.

---

• Arch-Enemy: To Mast Cell and B-Cell, targeting them above all other cells due to their actions being the catalyst for the excess histamine response, though it's certainly not choosy about going after basically any other cell that gets in its way.
• Destructive Savior: While it is medication designed to abate allergy symptoms, it's bad news for the cells in the body, as it attacks them indiscriminately and devastates the surrounding landscape.
• Eye Beams: Uses this to introduce itself.
• Gatling Good: Has one on each hand.
• Killer Robot: Attacks everything indiscriminately and disproportionately.
• Monster of the Week: Episode 5 of the anime/Chapter 2 of the manga, though it isn't so much a "monster" as it is a Destructive Savior that indiscriminately attacks the Cedar Allergens and the cells trying to protect the body from them.
• Mood Whiplash: After obliterating a large chunk of city, the steroid runs out of power and pops out confetti, saying "Thank you for your patronage!" in a dissonantly polite voice.
• Person of Mass Destruction: Its damage output far exceeds that of any cell or invader, as it all but levels every structure in the immediate vicinity with its ordnance.
• Soundtrack Dissonance: Once the steroid is identified, grand, upbeat classical music plays as it wreaks havoc.
• There's No Kill like Overkill: The steroid shoots everything in its vicinity to get the cells to stop reacting to the cedar pollen allergen. In real life, it's a better idea to take an antihistamine or nasal spray for allergic rhinitis, so the host overdid the medication by swallowing a steroid pill.
• When All You Have Is a Hammer…: Its single job is to stop the body from producing excess histamine by any means necessary, including laying waste to everything in sight.

Influenza

The flu virus, which parasitizes normal cells and converts them into zombie-like creatures.

---

• The Bus Came Back: After the influenza outbreak of chapter 3/episode 3, they return in chapter 21. This time, however, it is a different kind of influenza, adapted to the defenses of the body thanks to their Antigen Shift.
• Evil Evolves:
  • By the end of episode 3, a single infected cell remains. When Effector T. Cell tries to destroy it, he is instead easily defeated by the virus, and B Cell's antibodies fail to do any harm to it. Then U-1146 notices it has evolved to influenza A. Cue everyone realizing how screwed they are.
  • In chapter 21, the influenza returns to the body. However, thanks to the high mutability of the virus, it evolves once again. This time they are defeated thanks to Dendritic Cell's cytokines (AKA a bunch of embarrassing photos of all the cells of the immune system that turns them into unhinged killing machines).
• Monster of the Week: Of chapter 3 of the manga and episode 3 of the anime, respectively.
• Our Zombies Are Different: Unlike standard zombies, these guys can infect other cells just by spreading the virus spores to nearby normal cells, which makes them a pain to contain and kill.
• Parasite Zombie: The infected cells are parasitized by the influenza virus, that turns them into mindless zombies.
• Pokémon Speak: They tend to only make hissing sounds, "SHA".
• Recurring Boss: Appear two times in the series; one in chapter 3 and another one in chapters 21 and 22.
• Tornado Move: They produce stomachache by running in circles in line and creating tornadoes.
• Truth in Television: Unlike the bacteria, which are anthropomorphic villains, the viruses are inert, inanimate objects that indeed look just like they do in real life.
• Zombie Apocalypse: The virus consists of small red balls with sticks emerging out of them (that's how the virus looks in real life) that work by attaching themselves to the heads of Ordinary Cells, turning them into zombies.
• Zombie Gait: Averted. These zombies run fast and can even climb buildings to get to the other normal cells.

Vibrio parahaemolyticus

Voiced by: Itaru Yamamoto (Japanese), Armen Taylor (English)

A bacterium that causes gastrointestinal disease.

---

• Animal Eyes: He had insectoid compound eyes, while his minions only had one eye each.
• Flunky Boss: Brings in a group of floating bacteria minions when invading the body.
• Kill It Through Its Stomach: How he meets his end at the hands of U-1146 after swallowing him.
• Monster of the Week: Subverted. It looks like he is going to be the one of chapter 5/episode 4, but he is quickly killed by U-1446 before the true threat of the episode appears.
• Mook Maker: Spawns smaller bacteria to fight for it.

Anisakis

A parasitic nematode that attacks the digestive system.

---

• Curb-Stomp Battle: Gives one to the neutrophils, who are unable to harm it. Then on the receiving end by Eosinophil, who kills it with one hit of her weapon.
• Glowing Eyes of Doom: Makes its entrance with this as it emerges through the stomach wall.
• Mighty Roar: Shouts one strong enough to send all of the neutrophils flying away.
• Moby Schtick: The way Eosinophil kills it with a harpoon has shades of this.
• Monster of the Week: The main threat of chapter 5/episode 4, upstaging the Vibrio parahaemolyticus who appeared at the beginning of the chapter, who is easily killed by U-1146.
• Rent-a-Zilla: Is presented as a giant behemoth who destroys everything in sight.
• Slippery as an Eel: Though the anisakis is a parasitic nematode worm and not a fish, in this series it's presented with a head akin to that of a moray eel, instead of the worm-like head it has in real life, probably to make it more intimidating.

Pseudomonas aeruginosa

Voiced by: Riki Kitazawa (Japanese), Bill Rogers (English)

A bacterium that can cause several afflictions. Attacked AE3803 in her childhood as an erythroblast.

---

• The Bully: The reason why he infiltrated in the body was to torment smaller, weaker cells to his own amusement.
• Color-Coded Characters: It has a green colour similar to its cultures. This is also what its species name "aeruginosa" (copper-rust) comes from, although it could also be a reference to the pyoverdin pigment that the actual P. aeruginosa produces.
• Cyclops: Is a relatively big bacterium who only possesses one big, yellow eye.
• Evil Is Petty: Unlike other bacteria, he doesn't needs the nutrients of the body to survive; he just wants to pick on (and later kill) smaller cells for fun.
• Eye Scream: When he attacks her, AE3803 (as an erythroblast) throws her hat into his eye, causing him to scream in pain.
• Eyes Do Not Belong There: Can grow eyes and mouths on his tentacles. AE3803 and U-1146 as kids were terrified when he uses this as intimidation.
• For the Evulz: His motivation to attack those weaker than him is basically because he wants some fun.
• Mook: One of them acts as this along with other bacteria during the scratch episode. He is quickly killed by the neutrophils.
• Smug Snake: He is confident and arrogant while attacking those who are weaker than him, but he is easily killed by the neutrophil teacher of one strike without many problems.
• Starter Villain: While he isn't the first infectious threat to be featured in the series, In-Universe he is the first one that Red and White Blood Cell encounter, as he had menaced them back when they were kids.
• Truth in Television: He's the most blatantly For the Evulz of all the pathogens seen in the show, which is a perfect metaphor for the Pseudomonas aeruginosa's nature - unlike other dangerous germs, they don't need a host body to survive and reproduce efficiently, but when given the opportunity, they still cause very dangerous infections just because they can.
• Villain of the Week: Of chapter 7/episode 6.
• Would Hurt a Child: He enjoys bullying young cells by slapping them with his tentacles.

Bacillus cereus

Voiced by: Kosuke Toriumi (Japanese), Joe Zieja (English)

An opportunistic bacterium that invades the body during the heatstroke episode.

---

• Bio-Armor: All of his body, except for the face, is covered in white biological armor which can withstand high temperatures.
• Combat Tentacles: Has lots of them. He also has others to move through his environment.
• Dirty Coward: He prefers to run from the Neutrophils and mess with them, rather than confront them personally, as he knows they are stronger than him.
• Evil Gloating: Starts to tell U-1146 how their world is about to die and that they don't have any chance to win against the heat that's menacing the body. Doesn't stop U-1146 from fighting against him.
• Evil Laugh: Does this all the time, especially when he has the upper hand over his enemies.
• High-Pressure Blood: Spurts a geyser of blood once U-1146 catches up to him, though that may be just U-1146's pay back for all the trouble he had done.
• Kick the Dog: Noticing some red blood cells reaching for the last pitcher of buckwheat tea, he grabs it and dumps it to the floor right in front of the dehydrated White Blood Cell, for no other reason than just because he can.
• Oh, Crap!: Has a spectacular one once U-1146 reappears behind him after the body is rehydrated.
• Smug Snake: He's full of himself and his victory, once he manages to escape from the neutrophils and defeat U-1146. The fact that U-1146 kills him easily (and violently) after the heatstroke is properly resolved speaks volumes about how weak he truly was.
• Tempting Fate: After defeating U-1146, he starts to claim that now the body is his and no one can stop his victory... Seconds later, the body is re-hydrated, the cells are refreshed and U-1146 appears behind him...
• Villain of the Week: Of chapter 6/episode 11.
• Worf Had the Flu: His virulence is quite low, but a heat stroke leaves the immune system unable to deal with him properly, allowing him to defeat U-1146.
• Yellow Eyes of Sneakiness: A yellow-eyed, sneaky little pest who wants to take over the body.

Dengue Virus

The virus that causes dengue fever, which infects the body after being brought in by a mosquito bite.

---

• Blow You Away: Once the mask is attached to the Langerhans Cell, they develop the ability to create powerful gusts of wind.
• Monster of the Week: In chapter 16 of the manga.
• Parasite Zombie: The infected Langerhans Cells are parasitized by the dengue virus, that turns them into zombies with the ability to manipulate wind.
• Pokémon Speak: The only thing the infected Langerhans Cells are able to say once they are infected is "Deng".
• Tengu: The overall motif of those who are infected by the dengue virus, since in Japanese "dengue" is pronounced in a very similar way to "tengu". The victims wear tengu masks that clamp to their faces and gain Blow You Away powers, referencing how tengu are often associated with wind.
• Zombie Apocalypse: The virus consists of Tengu masks with tendrils that clamps the mask to the victim's face. This affects Langerhans Cells, turning them into super-powered zombies.

Rhinovirus

The infected cells.

The virus itself.

Voiced by: Makoto Furukawa

The virus responsible for the common cold.

---

• Color-Coded Eyes: As shown in the anime adaptation, the Rhinovirus-possessed Cell that we follow has green eyes, signifying that he's untrustworthy.
• Hoist by His Own Petard: Thanks to the traces of RNA it left on a prank gift, Killer T Cells were able to mobilize and easily track it down for a quick cleanup.
• Monster of the Week: Of chapter 11 of the manga.
• Our Zombies Are Different: Unlike the Influenza Virus, they still have some degree of self-control and personality. One affected cell even played pranks on Killer-T, U-1146 and Helper-T Cell and targeted an Ordinary Cell's cloning machine.
• Parasite Zombie: The infected cells are parasitized by the rhinovirus virus that turns them into zombies. This one however at least have some degree of personality, as they like to play pranks on others.
• Pokémon Speak: Communicates by saying "Keh".
• The Prankster: An evil variation. Loves to play pranks on other cells (particularly, the ones of the immune system, as Killer T Cell, U-1146 and Helper T Cell all become victims of his antics), but at the end of the day, it's a virus that wants to take over the body.
• Troll: It loves playing pranks, and it gains Ordinary Cell's trust by running circles around the various immune cells.
• Zombie Apocalypse: The virus consists of a hat with stars on it (based on how the virus actually looks, believe it or not) and teeth inside that attaches itself to the heads of Ordinary Cells, turning them into zombies.
• Zombie Gait: Averted. Like the Influenza, infected cells can spread fast enough to cover a neighborhood in a span of two pages in the manga.

Cancer Cell

Disguised

True Form

Voiced by: Akira Ishida (Japanese), Khoi Dao, Laura Stahl (young) (English)

A cancer cell. First masquerading as a normal cell, he quickly reveals himself as someone who wants to take down the entire body, in revenge for being hunted all his life.

---

• And There Was Much Rejoicing: An in-universe case. As he dies, the other cells celebrate his demise, as it marks the end of a terrible threat to the whole body. Out of universe, the fans' reaction was markedly different.
• Arch-Nemesis: Is this with Killer T Cell Squad Leader and Natural Killer Cell. Holds a particular grudge against Killer T Cell for calling him a "Buggy Bastard" which is what the cells who hunted Cancer Cell in his youth called him.
  "I hate Memory T's and NK's guts. I want to smash everything that's dear to them."
• Artistic License – Biology: From a real life perspective, while Cancer Cells are very nasty and damaging to the body, they don't directly hurt cells and instead indirectly harm them by depriving the body of nutrients or taking up healthy tissue. They are unable to directly attack immune cells like this Cancer Cell has shown the ability to do so.
• Back from the Dead: Due to his antibody information and genes being leaked, he manages to be rebuilt by Chapter 23.
• Berserk Button: Call him a "Buggy Bastard" and see what happens.
• Big Bad: He acts as the Arc Villain for the "Cancer Cell" arc as well as the "Return of Cancer" arc, being the only specific individual antagonist to directly antagonize the cells for more than one chapter/episode (every one of the germs constitute a swarm of their kind, so when they show up again in more chapters/episodes, it's different individual germs). With him genuinely coming back to life with his memories intact in the "Return of Cancer" arc, he gets upgraded from Arc Villain to genuine Big Bad, as no matter how many times he's killed he'll just keep on coming back for another round of trying to destroy the body, as his very existence is just an error in the genetic coding of all cells that will continuously pop up despite the cells' best efforts.
• Body Horror: Looks like a normal generic cell, but with deformed limbs and head.
• The Bus Came Back: Is rebuilt by Chapter 23, due to his antibody information containing his genes somehow being leaked.
• Came Back Strong: He was fairly strong the first time around, but when he's rebuilt, his strength has increased, the range and techniques of his Voluntary Shapeshifting has expanded, and on top of that, he has caused Regulatory T Cell to side with and protect him.
• Driven to Villainy: He argues that his only crime was coming into existence and by no choice of his own, where he immediately gets hunted down by immune cells and watches one of his comrades getting slaughtered. This left him bitter and vengeance driven and decides to take it out on the whole body.
• Dying Smirk:
  • The first time he's happy that U-1146 hears him out and acknowledged him as a cell even if he has to kill him for the sake of the body.
  • The second time, he's fine to be killed by someone he considers a friend, which somewhat disturbs U-1146.
• Early-Bird Cameo: In the anime; During the scrape wound episode, he helps AE3803 back up when she trips running away from the bacteria.
• Evil Counterpart: Can be seen as one towards Ordinary Cell; on top of looking like him, while Ordinary Cell wants to do more than what he was assigned and to help the body, Cancer just wants to be normal but decides to destroy the body when that's not an option.
• Evil Makes You Ugly: Inverted. It's more his ugliness as a defective cell that was in part what led him to become evil.
• Evil Plan: After cornering him, Natural Killer Cell explictly asks him what his "evil plan" is, but he refuses to tell her until after he has thrashed her, Killer T Cell Leader and U-1146. That was his evil plan, revenge on the Immune System which hunted him like a monster. He follows this up by announcing that he will replicate without limit until the body can no longer function.
• Expy: He's a clear reference to Ken Kaneki in both appearance and powers.
• Faux Affably Evil: Particularly towards White Blood Cell. His soft-spoken and polite manner of speech only serve to highlight his twisted and deranged nature.
• Growing Wings: He sprouts two wings (made of flesh) from his back when he's about to take over the body. Fortunately, he is stopped by a well-thrown cleaver (courtesy of Macrophage) before he can get any further.
• Hidden in Plain Sight: Can make himself look like a perfectly Ordinary Cell, if needed. He uses this to lure the Immune cells back to his hideout, by pretending to be attacked by another cancer cell.
• Horror Hunger: Several Cancer Cells are seen viciously devouring food with insatiable hunger, to the horror of the Red Blood Cells delivering it to them. Truth in Television as Cancer Cells produce cytokines which causes more nutrients to be delivered to it so it can metastasise.
• I Die Free: A Deconstruction, since he sees himself as being oppressed and hunted by the immune system simply for existing, and his plan is to kill the entire body before they can kill him. In his view this makes him "free" for breaking the cycle of existence for all cells. it's mostly an attempt to justify his Suicidal Cosmic Temper Tantrum rather than any actual attempt at being "free".
• I Just Want to Be Normal: Cancer's main motivation. He feels victimized because he was born a cancer cell due to no fault of his own (it's implied the technician on duty messed up because they were tired), and has been hunted like a beast by cells who should have been his friends. Now he wants everyone else to experience the same thing as he hunts them and ultimately destroys the body.
• I Just Want to Have Friends: Part of his hangup is that the Immune cells who were supposed to be his guardians instead hunted him down, thus driving him to intense loneliness. So he tried to copy himself to cure his loneliness. His HQ is plastered with signs saying, "MAKE MORE FRIENDS!"
• It's All About Me: He knows that his very existence means death for the world and millions of innocent cells and he doesn't care. All he cares about is getting revenge on the Immune Cells who hunted him for being defective.
• Knight of Cerebus: While fights against germs can be pretty brutal, the villainous characters are typically portrayed as cartoonishly evil and hard to take seriously which fits with the lighthearted tone of the series. This all changes when Cancer Cell appears, bringing about a whole new level of despair and ups the stakes greatly, especially given he's a Tragic Villain. He's also the closest thing this series has got to a Big Bad.
• Lovecraftian Superpower: His abilities involve lots of Body Horror, Combat Tentacles, Shapeshifter Weapon, Shapeshifter Mashup and Power-Upgrading Deformation. It's not a pretty sight.
• Meat Moss: Can create tumor-like extensions from his own flesh to attack and subdue Immune Cells.
• Me's a Crowd: As a cancer cell, he's constantly multiplying with no regard for restrictions.
• Multi-Armed and Dangerous: Has the ability to multiply his limbs to fight. Often combines this with Combat Tentacles.
• One-Man Army: He can manhandle three powerful Immune Cells at once, each of which are usually capable of taking on swarms of nasties on their own.
• Power Echoes: In his true form his voice has a reverb effect to add to his threatening vibe, and contrast with his Ordinary Cell disguise.
• Put Them All Out of My Misery: Believes it's unfair that he was born against his will as a cancerous cell and exists solely to be hunted down and destroyed to protect the body. Therefore, he resolves to make use of his function and destroy the entire body and all its inhabitants, rather than letting himself be killed to preserve their lives.
• Revenge: His primary motivation for the chaos he causes, is to give the Immune Cells a taste of what it's like to be hunted and helplessly overpowered just as he was.
• Shapeshifter Mashup: His final attempt to take over the body involves making a "tower" of an unholy amount of flesh, limbs, heads and veins.
• Shapeshifter Weapon: In addition to creating additional arms, he can also shape his main arms into blades or shields.
• Suicidal Cosmic Temper Tantrum: Wants to destroy the world (i.e. the body) in retaliation for having been hunted all his life.
• Then Let Me Be Evil: Bitter over being treated as a defective anomaly from the instance he came into existence, he decided that since he was branded a threat then he would be the biggest threat to the body possible.
• This Cannot Be!: His reaction when NK (powered up by laughter) defeats him easily with one strike.
• Tragic Villain: His actions are motivated from the fact that he had to live in constant fear of dying his whole life when he never intended to do anything bad and just wanted to live his life peacefully. All the evil things he does are acts of desperation after being persecuted since the moment he was born.
• Voluntary Shapeshifting: Can shapeshift into bizarre forms to help fight better. It usually involves extra arms of differing sizes.
• Wake-Up Call Boss: After dealing with bacteria, viruses and parasites, who were defeated with relative ease and only lasted a maximum of one chapter, he ends up being a greater challenge for the immune system than the previous enemies, lasting more than one chapter and even defeating U-1146, Killer T Cell and NK until the reinforcements who AE3803 called appear.
• We Will Meet Again: Before being killed by U-1146, he says that one day he will return to the body and kill him. In response, U-1146 says that, no matter how many times he comes back, he and the other members of the immune system will be sure to deal with him again and again. Sure enough, he returns in Chapter 23, and when he's defeated again, his last words are "See you again... White Blood Cell."
• Woobie, Destroyer of Worlds: He was born wrong, through no fault of his own, and from the moment of his birth lived in fear and confusion of why he was being hunted down by the cells who were supposed to be his friends. When he realizes that he is a freak and supposed to die, he goes into a rage and decides to take down the entire body with him.

Helicobacter pylori

Voiced by: Jun Fukushima (Japanese)

A large worm-like creature found in the stomach. They are bacteria resistant to acid and can cause gastrointestinal diseases.

---

• Achilles' Heel: H. pylori are weak to lactic acid produced by lactic acid bacteria. Unfortunately for this guy, a bunch of them was exactly in the place of its invasion.
• Creepy Centipedes: Appears as a giant centipede with five eyes on its head and tentacles that it can use as drills or to lift itself up.
• Monster of the Week: In chapter 20 of the manga.
• Visual Pun: Helicobacter Pylori has a set of helicopter rotor-like blades on its head.

Opportunistic Bacteria

Bacteria found in the gut and digestive tracts. Their name is a general term for bacteria that neither help or harm the body, but side with whichever holds the advantage.

---

• Chronic Backstabbing Disorder: As implied in their name, they partner with whichever side is stronger and will abandon them at a moment's notice if the tides are turned. They abandoned the harmful bacteria when the Lactic Acid Bacteria came to the rescue. The Neutrophils don't buy any of it and kill them anyway.
• Little Bit Beastly: One of them is represented as a kitsune.
• Ridiculously Cute Critter: Not so much as the good ones, but still cute, befitting their nature as opportunistic bacteria in a series where Beauty Equals Goodness.
• Zerg Rush: They are about 70% of the bacteria found in the gut. The harmful bacteria try this tactic with the opportunistic bacteria. Unfortunately for them, the lactic acid bacteria still hold the numerical advantage.

SARS-CoV-2

The "Novel Coronavirus", also known as COVID-19. It infects the body in the last two chapters, causing dangerous side-effects from the cytokine storm.

---

• Almost Out of Oxygen: The hypoxia caused by the thrombosis and followed by damage to the lungs is noted to cause multi-organ failure if it continues. Thankfully, the virus is stopped during the lung inflammation phase.
• Final Boss: The manga quickly ends after Coronavirus's defeat.
• Hit-and-Run Tactics: They show up, irritate Killer T Cells and run away, causing T Cells to start attacking regular cells out of stress and paranoia.
• Killed Offscreen: After anti-inflammatory cytokines calm down Killer T Cells, it's stated that they've defeated Coronavirus, however, that isn't seen.
• Ninja: Its theme, mirroring how it can spread across the body and infect others for a week before any symptoms show up.
• Real Life Writes the Plot: Compared to other infections in the series, this one is much more prominent at the time of the manga's writing, that being the end of 2020. A note in the last chapter states that its mechanics are still not entirely understood.
• Suspiciously Similar Substitute: To Influenza, with the main difference being the tactics utilized.
• Weak, but Skilled: Individually, Coronavirus is one of the weakest viruses, dying to a single punch. However, it's more strategic than other viruses, trying to avoid T Cells entirely and indirectly harming the body through Collateral Damage.

Other

The Narrator

Voiced by: Mamiko Noto (Japanese), Karen Strassman (English)

---

• Dissonant Serenity: The narrator always has the same cheerful tone when explaining concepts and cell components, even when the body is succumbing to heat stroke, losing massive amounts of blood, and the like.
• Ms. Exposition: Provides information and explanations regarding the workings of the various cellular organisms and structures, particularly whenever Red Blood Cell and White Blood Cell are unable to ask and provide explanations themselves.
• Narrator: One that is external to the story. The narrator doesn't discuss any plot points, only providing information to educate the audience. This narrator seems not to be omniscient, though — in the heatstroke arc, she echoes the cells' puzzlement at the source of the miracle fluid entering the body.

The Human

The human that the story is set inside.

---

• Ambiguous Gender: Their gender is never revealed.
• Audience Surrogate: Explicitly stated in the opening narration to represent the audience's own bodies. This seems to be the sole reason for keeping their identity a mystery.
• Butt-Monkey: This poor person sure goes through a lot, though possibly Downplayed depending on how much time passes between each major bodily disaster.
• The Faceless: Despite the fact that they are technically on screen in every single shot, the audience never learns what they look like.
• Genius Loci: A given, since the entire series takes place inside of them. Also Downplayed since nearly everything in this setting appears to be man-made.
• Minor Major Character: They have never properly appeared before, yet they enable the entire series to be possible to begin with.
• Near-Death Experience: In Episodes 11 and 12, they suffer from a hemorrhagic shock injury that comes very close to killing them, and are only saved by an emergency blood transfusion.
• No Name Given: No characters in particular ever refer to its host (the world itself) by name.
• Plot Allergy: The closest thing we ever get to an identifying trait from them is that they are severely allergic to cedar pollen, which forms the plot of volume 2 of the manga and episode 5 of the anime.
• Unknown Character: Very little is known about their identity aside from clearly being the outdoors-type of person, but the entire story still relies on them existing.
• Vague Age: The age of the host is never made clear.
• The Voiceless: Downplayed. They are never heard outright speaking, but they still occasionally can be heard sneezing and/or coughing in the background.

---