Manga / Cells at Work!

aka: Hataraku Saibou

Though we don't know who you are!
For your sake, we're working hard!
All of us together are supporting you with all of our hearts!
No matter what kind of strife!
Each of us would risk our life!
We always take pride in what we do and health comes first!

—Mission! Health Comes First!, the theme of Cells at Work!

The human body is a vast, wide network of paths, tubes, and chemicals. To keep all of that in order, it has 37.4 trillion cells set to do their part. Supplying oxygen to muscles? Red blood cells can handle it. Remembering the body's reactions to foreign substances? Let the memory cells jot it down. And woe to the poor germ that has a run-in with a Neutrophil or a Macrophage. Between keeping the body clear of antigens and delivering the proper materials to its different parts, there's a lot of work to be done to keep everything in top shape. It may sound daunting to the average person, but to a cell, it's all in a day's work.

Cells at Work! (Hataraku Saibou) is a manga by Akane Shimizu about all the wonders of the human body, shown to us as humans themselves. The manga began with a one-shot pilot called The Story of Cells (Saibou no Hanashi) and ran in Shonen Sirius from 2015 to 2021. The manga has been licensed for North American release by Kodansha Comics.

An anime adaptation by David Production began airing on July 8, 2018. It is licensed by Aniplex USA and is streamed internationally through Crunchyroll, spanning 13 episodes. The English dub of the anime was released for Blu-Ray on August 27, 2019. The anime is also noted to be the first title where Aniplex USA dubbed the opening song in English.^note Anime titles that are dubbed into English tend to leave the opening and ending songs left sung in Japanese, as it's generally too tedious to find a voice actor/actress who has some singing capacity. A fourteenth "special episode," "Common Cold," was released months after the original run of the anime as a Christmas Day special. A second season was announced in 2019, and premiered on January 9, 2021.

Other media includes

• Shōsetsu Hataraku Saibō (July 12, 2018): A Light Novel adaptation of the manga written by Yui Tokiumi, illustrated by Akane Shimizu and published by Kodansha.
• Cells at Work Stage Play (Tainai Katsugeki Hataraku Saibō) (2018): A stage adaptation written by Keita Kawajiri and held at Tokyo's Theatre 1010 from November 16 to 25.
• Always Cells at Work! (Itsudemo Hataraku Saibō) (2019): A Tower Defense game released for mobile.
• Cells at Work! The Return of the Strongest Enemy. A Huge Uproar Inside the Body's "Bowels"! ("Hataraku Saibō!!" Saikyō no Teki, Futatabi. Karada no Naka wa "Chō" Ōsawagi!) (September 5, 2020): An animated theatrical movie based on a story from Volume 5 of the original manga series. It may be the most dramatic movie title with the word "bowels" in the title ever.
• A live-action film adaptation was announced by Kodansha and Flag Pictures on March 20, 2023. It will be directed by Hideki Takeuchi and the script of which will be written by Yuichi Tokunaga.

The series has received several spinoff titles over its run, further exploring parts of human anatomy Shimizu couldn't fit into the original:

List of Spinoffs

• Cells at Work: Bacteria! (Hataraku Saikin), which focuses on the battle between good and bad bacteria in the intestines. Written by Shimizu and illustrated by Haruyuki Yoshida, and ran in the Shōjo anthology Nakayoshi from 2017 to 2020. An English translation was released by Kodansha Comics starting in July 2020.
• Cells NOT at Work! (Hatarakanai Saibou), about, well, cells that don't work. It primarily focuses on Erythroblasts; but rather than the immature blood cells being kids, they're full blown young adults that grew up into lazy shut-ins that refuse to enucleate. Written by Shimizu and illustrated by Moe Sugimoto, and runs in Shonen Sirius like its parent comic. An English translation was released by Kodansha Comics starting in October 2019.
• Cells at Work! CODE BLACK (Hataraku Saibou; Black), a much darker series about the life of cells in an unhealthy body. The human smokes, drinks too much, is under high stress, never exercises, has high cholesterol and practices unsafe sex, leading the cells inside to overexert themselves. The first spinoff not to be written by Shimizu, instead being penned by Shigemitsu Harada and illustrated by Issei Hatsuyoshi. Ran in the Seinen magazine Morning from 2018 to 2021. Like the main series, the manga is licensed by Kodansha Comics in North America.
• Cells at Work and Friends! (Hataraku Saibou Friend) is similar to Cells NOT at Work! in that it's also a Slice of Life manga. It's about a Killer T-Cell who wants to make friends but doesn't want to compromise his tough image — and no, this isn't the same Killer T as in the original manga. The second spinoff not to be written by Shimizu, Friends is instead penned by Kanna Kurono and illustrated by Mio Izumi. It runs in Bessatsu Friend, a shoujo anthology. An English translation was released by Kodansha Comics starting in October 2019.
• Cells at Work: Platelets! (Hataraku Kesshoban-chan), which focuses on the ever-popular and cute Platelet team from the original manga. Written by Yuuko Kakihara (who was on the anime's writing team) and illustrated by Yasu (of Toradora! fame), this spinoff runs in Monthly Shounen Sirius. An English translation was released by Kodansha Comics starting in July 2020.
• Cells at Work: Baby! (Hataraku Saibou BABY), which focuses on the usual but in an infant's developing body while in the womb. This one has a more Super-Deformed art style, reflecting how the body's still yet to mature. It's drawn and penned by Yasuhiro Fukuda, and runs in Morning. An English translation was released by Kodansha Comics starting in July 2020.
• Cells at Work! Lady (Hataraku Saibou Lady), having much of the same content but aimed at adult women. The second manga written by Shigemitsu Harada, though illustrated by Akari Otokawa. Runs in Morning two.
• Cells At Work! White Brigade (Hataraku Saibou WHITE), which focuses on the fan favorite Neutrophils of the original manga and digs deeper into their daily lives and functions. Illustrated by Tetsuji Kanie, this manga runs in Sirius.
• Cells at Work! Illegal (Hataraku Saibou Illegal), which focuses on a body that partakes in drugs and other illegal activities and where the immune system functions like the Yakuza. Written and illustrated by Kae Hashimoto and runs in YanMaga Web.
• Cells at Work! Muscle, which focuses on the muscular system. Written and illustrated by Yuu Maeda and runs in Morning two.
• Cells at Work! Cat, which focuses on the cells within a cat's body. Written by Choco Aozora and illustrated by Meku Kaire and runs in Monthly Shounen Sirius.
• Cells at Work! Medicine, which focuses on various medicines. Written by Koma Warita and illustrated by Ryō Kuji and runs in Monthly Shounen Sirius.

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Here's today's trope delivery!:

#-C

• 2D Visuals, 3D Effects: The background Red Blood Cells in the Anime. AE3803 also becomes partially CG in a few scenes too.
• Acceptable Breaks from Reality: This show has Red Blood Cells deliver oxygen and other nutrients throughout the body and remove carbon dioxide and other waste products. In real life, red blood cells only deliver oxygen. Everything else is transported by dissolving in the blood plasma. Because the blood plasma isn't made of cells, there's no real way to portray this via Anthropomorphic Personification, so all of these deliveries are handled by the red blood cells instead.
• Action Girl: Quite a few of the immune cells are depicted as female, most notably Natural Killer Cell.
• Adaptation Expansion: The episode "Common Cold" expands on the number of pranks the Rhinovirus-infected cell and Ordinary Cell play on other cells: directing AE3803 to an alley with a long drop, switching the Macrophages' weapons with sports equipment, confusing the hell out of the Neutrophil squad by setting off their signals, and stealing Basophil's umbrella while it rains histamine. This has the effect of making the immune cells look less competent, though it gives Basophil an opportunity to remark about negligence in one's conduct that turns a utopia to a dystopia (i.e. "you'll be sorry").
• Air-Vent Passageway: Neutrophils use this to get the drop on their enemies, as a representation of their ability to transmigrate (pass through cellular tissue). In another chapter, U-1146 squeezes through a narrow crack in the wall.
• Alas, Poor Villain: Let it be known that a manga about the human body can get you to feel bad for cancer cells, of all things.
• Alien Abduction: Blood transfusion is depicted as this for the hapless Red Blood Cells involved. Similarly, a mosquito bite is depicted as a giant tube in the sky sucking out Red Blood Cells.
• Alien Blood: Subverted, the cells bleed cytoplasm (the internal fluids of a cell), but in the show it's depicted as looking like ordinary red blood.
• Alien Invasion: Bacteria and viruses are effectively presented as this. All of the human cells are represented as humans. By contrast, bacteria - being cells foreign to the body - span myriads of monstrous forms, but are still able to speak and have their own personalities, representing the fact that just like our own cells, they are still living organisms. Viruses, meanwhile, are presented as Starfish Aliens that cause a Zombie Apocalypse by hijacking cells. They do not speak, have no discernible personality, and don't even look like living things - which is appropriate, since it's questionable whether viruses in Real Life are even alive.
• Alone with the Psycho:
  • Happens to AE-3803 in episode 1. She found the Monster of the Week in a supply closet, and he proceeed to chase her. Thankfully U-1146 was able to save the day.
  • This also happened in the Flashback Episode. AE-3803 was training and got lost in the bone marrow. She saw a tentacle approaching, and was assuming it was the White Blood Cell instructor in disguise. The germ was real, and hunted her down. U-1146 was nearby and tried to save her, only he was also in training and had a rubber knife. They end up cornered, and in real danger of being killed.
• Always on Duty: Justified as this is the human body, the cells never have a moment's rest.
• And the Adventure Continues: The anime ends this way, with the cells going about their usual business.
• Animated Adaptation: A 60-second commercial showing an abridged version of the first chapter played in front of the first episode of Welcome to the Ballroom's adaptation. The series got a proper anime the following year.
• Anthropomorphic Personification: Each cell type is represented as a human being wearing a uniform to indicate it, as well as possessing some sort of quirk to emulate their real-life functions/capabilities. The white cells enjoy the widest range of designs because of the sheer variety of immune-related roles they perform.
  • Red cells wear red jackets and sunken berets that resemble real-life erythrocytes. Immature red cells, i.e., erythroblasts, have a red sphere on top of their berets, signifying that they still have a nucleus.
  • Neutrophiles have white skin and wear a white, soldier-like uniform that has several accessories. An antigen detector on their caps that perks up whenever there's an antigen nearby, knifes to tear bacteria apart, and a walkie-talkie to communicate their position and relay important information to other white blood cells. Their hair is white too.
  • Killer T lymphocytes wear a black, police-like uniform and a black cap that says kill. They don't wield weapons but are good at martial arts and tend to be very muscular.
  • Natural killer T lymphocytes wear a military training outfit with combat boots, shorts, and a black tank top. They are muscular as well and wield metallic sabres that, when cracked, turn into purple lightsabers.
  • Helper T lymphocytes wear a uniform akin to that of a high-ranking military officer and are far less brawny than the killer T cells. However, it's revealed they are picked from the best thymocytes cadets (i.e., the strongest and smartest ones).
  • Regulatory T lymphocytes wear an office uniform and headphones with a mic to coordinate with other immune cells into conjoint attacks or to alert them of a new threat.
  • Platelets veer more into Moe Anthropomorphism, as they are depicted as cute children working in teams to accomplish all sorts of tasks, such as netting several, adult-looking cells together for coagulation.
  • Macrophages wear white Meido uniforms as they are often tasked with cleaning in real life. Their weapons are huge, bladed or blunt weapons such as machetes and mallets. Their hair is a very light brown. When they enter the blood vessels, they turn into monocytes and put on yellow radiation protective suits, antigas masks and all.
  • B lymphocytes wear blue, janitor-like uniforms and wield big guns similar to those used to spray insecticide on crops.
  • Mast cells wear lab coats and work inside control stations that can release all sorts of regulatory molecules to the body.
  • Dendritic cells wear a green, park warden-like uniform and a peaked cap that has a small branch. Their workstations are trees. These two facts lampshade that their name is derived from "dendrites", which means "branches like a tree" in Greek. They are often seen carrying files that they use to active other immune cells.
  • Eosinophiles wear pink military-like uniforms with pink and white caps. Their weapon is a sasumata (think of a trident with only two prongs), something more fitted for the large parasites they fight.
  • Memory B cells wear a black and gray uniform that resembles what would a magician use. They have a running gag of spouting world-ending prophecies that are, in truth, just allergies.
  • Memory T cells are in charge of memorizing info about previous virus infections and wear the same uniform as killer T cells, just with memory on their caps. They also have notebooks on hand.
  • Basophils wear water-protective gear, complete with a hoodie, a mask, and an umbrella — kind of what a fisherman would use while on duty. They have a mysterious air as scientists aren't sure of what they do in real life.
  • Megakaryocytes, the cells that fragment off to produce platelets, are represented by pregnant women. A literal take on "baby factory".
  • Brain cells reassemble high-ranking executives and wear two-piece suits.
• Anthropomorphized Anatomy: The series as a whole personifies various cells of the human body and how they function.
• Artificial Human: How cell reproduction is usually portrayed. Most cells are shown growing in facilities before being sorted out by the Hematopoetic Stem Cells, while all Ordinary Cells have cloning machines in their homes.
• Artistic License – Biology: The series frequently shows its work, but there are some things it has to modify to fit into the setting.
  • Red blood cells don't transport nutrients (stylized as food baskets), aside from oxygen — the non-oxygen nutrients are dissolved in plasma and circulate freely around the body. They also don't transport medication either, which Red Blood Cell does to abate a cedar pollen allergy. However, since the plasma isn't depicted as anything other than the surrounding air, it's more convenient for the series to depict nutrient transport as another part of the courier service, essentially combining the functions of plasma into the jobs of the Red Blood Cells. In the Anime, this is lampshaded by kouhai Red Blood Cell, who states that the transportation of nutrients is an "extra task" undertaken by Red Blood Cells that doesn't fall under the scope of their jobs.
  • Red blood cells last around 90 to 120 days in circulation. Neutrophils don't last more than 2 days. It would be highly unlikely for the same erythrocyte and neutrophil to keep meeting one another in separate incidents, which U-1146 mentions the first time he and AE 3803 part ways. This is handwaved In-Universe by the fact that cell lives are equated to the frequency they change their clothing.
  • Neutrophil U-1146 single-handedly survives way too many attacks to be reasonably expected from what is essentially the body's Cannon Fodder. Plot Armor is likely to blame here, although he is implied to be especially skilled among his peers.
  • Since they are depicted with human-like proportions, the cells are obviously not drawn to scale (though the Platelets are children because IRL they are tiny), because that would mean that Neutrophil would be twice as tall as Red Blood Cell, and Macrophage would tower above them all at nearly six times their size! And the Megakaryocyte, the progenitor of the platelets, is bigger than the Macrophage (up to nearly double its size)!
  • The pathogens are shown to be the size of the Neutrophils or even bigger, when realistically, they would actually be small enough for the neutrophils to swallow whole! Of course, that would be neither threatening nor interesting to watch.
  • The Anisakis worm is one hell of a badass: in the anime, it's portrayed as a terrifying Kaiju that threatens to rip open the stomach and devour all the cells. In real life, though, it's actually pathetically bad at invading human tissue, and in fact is only dangerous because it tries to burrow through the gut lining, fails to do so, gets stuck in the gut lining and dies, and then the immune system proceeds to Zerg Rush its already dead corpse, causing an allergic reaction. This was probably a conscious artistic choice, as it's precisely that way because the immune system thinks that it could tear through the stomach and devour all cells that this reaction ends up happening, and the entire show happens from their perspective.
  • B-cells don't switch which kind of antibodies they produce, though again to be fair, having to make an entirely new B Cell character for each needed antibody would be kind of a hassle. Also, B Cell's gun changes every time.
  • Antibodies fulfill way more roles than just being weapons. Granted, they do tag pathogens to neutralize them and hamper their development. However, they also serve to give rather detailed instructions to the immune cells ranging from which defense mechanism should be unleashed (e.g. phagocytosis, cytotoxicity, and cell lysis) to whether they should reproduce.
  • Effector T-cells don't revert to Naive T-cells for any reason. They will only become Killer or Memory T-cells. Again, as with the B-cell, it would be a hassle to change characters that much.
  • The Platelets plug up the wound with the bodies of the Red Blood Cells, when technically they would be piling themselves onto the fibrin clot, later roping in help from other blood cells to form a scab.
  • Epithelium and structural cells are depicted as buildings and not as living beings, though being as alive as blood cells are (then again, it would be awkward to show roads and walls made of people stacked together...). Instead, the living component is a "common cell" that lives or works in the building.
  • Chapter 15/Episode 10 treats Monocytes and Macrophages interchangeably when biologically, they have different development stages, which are typically not reversible. Monocytes are progenitors to Macrophages, and depending on the external signal can also differentiate into Dendritic Cells.
• Ascended Fridge Horror: "What would autoimmune disease look like in this setting?" has been a good question since the series started, and was addressed by BLACK in the episode/chapter where Killer T cells got so worked up by stress that they went after hair cells, and when gout caused the immune system to cause inflammation across the body. The main series manga ends with Coronavirus - the virus itself is not nearly as threatening as the cytokine storm resulting from the immune system continuously escalating.
• Astonishingly Appropriate Appearance: Justified since they are anthropomorphic personifications of the immune system. Special mention goes to the Neutrophils since they are pure white just like their namesakes.
• Ax-Crazy: The Neutrophils appear to be those nice, swell guys you could be friends with. That is unless you are a harmful bacterium; they then become unhinged literal murderous Blood Knights out to kill them indiscriminately. The only exception to this rule is Lactic Acid Bacteria that help the body.
• Back for the Finale: Many body-cells that have appeared throughout the anime series are given voiced cameos in Episode 12, despite not appearing in Chapter 17 of the manga, from which the episode was adapted. This is likely because the anime episode in question is the first of a two-part finale for the series.
• Badass Adorable:
  • The good bacteria are cute and cuddly creatures who are capable of fighting the harmful pathogens almost as well as the White Blood Cells. One particular Lactic Acid Bacterium in chapter 21 was able to cause serious damage to an H. Pylori that's hundreds of times its size, enough to drive it away from the gastric acid pool so that the Neutrophils can deal the killing blow.
  • Also the Platelets, who are willing to wander into battlefields and walk past hostile bacteria to do their duty, despite being little kids. Not for nothing U-1146 considers them their most trusted and reliable allies.
• Badass Teacher: Macrophages are the stronger type of Immune cell, who also serve as teachers to the erythroblasts.
• Battle Aura:
  • In "The Circulatory System", Red Blood Cell emanates a fiery aura when she's determined to do her job without anyone's help.
  • In "Erythroblasts and Myelocytes", the Neutrophil assisting Macrophage with the Pseudomonas puppet is so good as roleplaying as Pseudomonas (and terrifying the erythroblasts) that he exhibits the same purple aura as the bacterium itself.
• Beach Episode: Or the closest thing a body can get to a Beach Episode. The body takes an IV shot after getting heat stress that is represented as a giant tube that brings rain. The place then turns into a resort for the cells to cool off.
• Beauty Equals Goodness: The harmful bacteria are depicted as humanoid monstrosities, often with fangs, claws, or deformed body parts. The good lactic acid bacteria, on the other hand, are depicted as cute and cuddly. Opportunistic bacteria, who switch sides depending on which bacterial strain is currently on top, are in between, not being as monstrous as bad bacteria or as cute as good bacteria. Meanwhile, the human body's native cells generally appear as attractive as young people.
• Big Ball of Violence: B Cell and Mast Cell cause one in the background of episode 5 after the latter overdoes it on the histamines.
• Bilingual Bonus: The reason dendritic cells have a tree motif — their name is derived from Greek dendros, meaning tree.
• Blame Game: The cedar pollen allergy disaster becomes a blame game (and then a Big Ball of Violence) as Mast Cell and B Cell argue whose fault it was.
• Blood Is the New Black: Neutrophils tend to get their jumpsuits covered in bacterial cytoplasm often. U-1146 is practically never seen without his.
• Blood Knight: Quite literally with the immune system cells, most being different White Blood Cells, since they're blood cells that act like knights. U-1146 is a Knight in Shining Armor example.
• Book Ends :The last page of the final chapter is a call back to the last page of the first chapter when AE3803 says goodbye and good luck to U-1146 who is busy as usual killing bacteria to protect the human body [1]◊
• Boot Camp Episode: One chapter is a Whole Episode Flashback to when Helper T Cell and Killer T Cell were Thymocytes (developing T cells), which is depicted as them being rookies going through basic training during their time in the thymus.
• Boss Subtitles: When a cell type appears in every manga chapter for the first time, there'll always be a text box that introduces its functions. That includes the Red Blood Cells and the Neutrophils.
• Breather Episode: Episode 8, coming right after the first battle with Cancer Cell, is a relaxing episode that's about the circulatory system, with AE3803 attempting to finish a delivery without the help of other cells.
• Briar Patching: In order to save an Intestinal Epithelial Cell, U-1146 and squad comply with the bacteria's demands and not-so-subtly point out that they are heading towards a weak part of the intestine. It actually leads to a Peyer's Patch (no pun intended) where the bacteria are instantly surrounded at all sides.
  Intestinal Epithelial Cell: You see... up here there's a place where the villi are sparse and the membrane is thin...
  Neutrophils: [teary-Feyed] Nooo! Don't do it, Intestinal Epithelial Cell! Tell him Anything but That!!
• Butt-Monkey:
  • Whoever this manga takes place inside does not have an easy life. Among other things, they contract a hideous Anisakis worm from bad sushi; suffer severe allergy attacks; come down with dengue fever; and are horribly wounded and nearly die from blood loss.
  • Red Blood Cell AE3808 is a poor victim of bacteria attacks, cells yelling at her for transporting nutrients in the wrong location, gets wrapped up in a blood clot, and is in constant danger, all of which are Played for Laughs.
  • White Blood Cell U-1146, when he is not stealing the spotlight, gets to be this whenever AE-3808 is not around. Shining examples are him getting stuck in the blood clot, getting knocked down by bacteria only to be upped by the cell of the day, and usually gets caught by AE-3808's mistakes.
• Call-and-Response Song: The opening in English uses this format in the final few lines:
  Red Blood Cell: Are you working?
  Neutrophil: Yes, I'm working
  Macrophage: Are you working?
  Killer T Cell: Course I'm working!
  All: Working for you!
• Cast of Personifications: The manga is about personifications of cells that make up the human body, although it mostly focuses on the immune system. It also turns organs into places, like blood vessels as roads and the stomach as a giant kitchen.
• Casual Danger Dialogue: By Chapter 17/Episode 12, AE3803 and U-1146 are able to hold casual conversations while the latter is wrestling with and killing pathogens, much to the bewilderment of the former's kouhai.
  • The two protagonists have a Running Gag of sorts involving this, where no matter how dire the circumstances they bump into each other they still take a couple moments to greet each other.
• Cerebus Rollercoaster: The manga follows this pattern, with lighter arcs after a darker arc. The story starts with cells being introduced, after which Cancer Cell is introduced as an Arc Villain. followed by some more lighthearted chapters. Then suddenly, the body gets into a hypovolemic shock and almost shuts down. This is followed by the lighthearted Lactic Acid Bacteria arc, which is then followed by Cancer Cell's revival.
• Chained Heat: Erythrocyte AE3808 and Neutrophil U-1146 are briefly stuck together by the bacterial capsule of the Pneumococcus in episode 1.
• Childhood Friends:
  • U-1146 and Eosinophil have known each other since they were young.
  • Killer T Cell, Regulatory T Cell, and Helper T Cell were all in the same graduating class in Thymus school. They're not exactly friends, though.
• Circling Birdies: In the Staphylococcus Aureus chapter/episode, the dazed Neutrophils have circling stars around their heads as they thank the Macrophages/Monocytes for dealing with the bacterial invaders.
• Color-Coded Characters: Shimizu provides a helpful color guide for the cells:
  • Red blood cells (as well as neutrophils/white blood cells) get their obvious assignments.
  • Killer T cells are black.
  • Monocytes are yellow.
  • Eosinophils are pink.
  • Dendritic cells are green.
  • B cells and basophils are blue, but B cells are a lighter shade than basophils.
• Comical Overreacting: A significant chunk of the show's comedy derives from this, as it runs on the Mundane Made Awesome nature of humanizing ordinary events as felt on a microscopic scale. The allergy episode in particular is a nonstop cavalcade of this, representing how an allergy is quite literally your body overreacting to what should be a very minor issue.
• Contemplate Our Navels: Basophil is an immune cell with a raincoat and umbrella who stands around, making long, bombastic speeches that are supposed to inspire other white blood cells. In real life, basophils signal other cells to act by releasing inflammatory compounds as part of immune responses.
• Contrived Coincidence: Whenever AE3803 is in trouble, be it foreign invaders or just her getting plain lost, Neutrophil U-1146 is almost always the one to save her. This has led to some Ship Tease moments between the two. AE3803 even lampshades this while reminiscing about the myelocyte who saved her from a Pseudomonas bacterium. She doesn't remember his face because it happened a long time ago, and after taking a moment to wonder if that was U-1146, she dismisses it as too much of a coincidence. Both 3803 and 1146 comment on how big a coincidence it is that despite there being 37 trillion cells in the body, the two of them eep bumping into each other.
• The Corruption: The Influenza virus, depicted as a mushroom-like parasite.
• "Could Have Avoided This!" Plot: The allergy plot is a subversion. Near the end, Neutrophil realizes that the immune system shouldn't have reacted to the cedar pollen at all (allergens are harmless substances that the immune system responds to regardless). However, despite knowing this, the plot could not have been avoided because everyone was doing their job.
• Courier: Red Blood Cells are depicted as employees of a package delivery service, delivering vital items like oxygen to various parts of the body.
• Crapsaccharine World: Despite the cutesy art style, the human body is portrayed as a very harsh place to live in. The only saving grace is that our cells aren't actually sentient beings, so they don't have to suffer through all of this.
  • Cells are born with one predefined job that they must perform their whole life whether they like it or not. Brave New World, anyone?
  • Killer-T Cells that underperform are executed on the spot (albeit via Trap Door to make it not as gruesome). Only 2-3% of thymocytes survive the selection process.
  • Every viral infection is basically a Zombie Apocalypse where the only option is to have Killer-T Cells inflict a Mercy Kill on every victim before they can infect more cells. These "zombies" can be the Killer-T Cells' previous friends and neighbors, so they have to be very detached and emotionless in order to be able to fulfill their job.
  • Cancer cells are hunted down and killed simply for being made wrong, which is of no fault of their own. Not even looking like kids dissuades their killers from trying to take them out before they can multiply because the consequences of not doing so would be disastrous.
  • Heck, even the tiniest of scratches or cuts will result in the death of thousands of blood cells who are sucked out through the wound.
• Crippling Overspecialization:
  • Eosinophil is very weak against bacteria and viruses. But if a parasite invades the human body, she becomes badass enough to kill it in one hit.
  • Effector T Cell is a tremendous powerhouse... against the specific threat he's made for (in this case, influenza viruses). Against anything else, even a variant strain, he's useless.
• Curb-Stomp Battle: U-1146 as a child myelocyte tried to protect AE-3803 from a bacteria. He's in training, however, with a toy knife, and tiny. The germ swiftly curbstomps him.
• Cuteness Proximity: Just about every cell feels at ease watching the adorable little Platelets work.

D-M

• Damsel in Distress: The female Red Blood Cells (especially AE-3803) tend to be this, along with the male Red Blood Cells who also count as Distressed Dudes. Justified, since they aren't made to combat germs and their only role is to make deliveries; thus, they have no way of defending themselves against foreign invaders and can only run away while the White Blood Cells destroy the invaders.
• Darkest Hour: The hypovolemic shock (extreme blood loss) incident (covered in the manga and anime as Chapters 17-18 and Episode 12 respectively) is probably the darkest and most difficult moment of the whole series, probably even more than the Cancer Cell arc. Due to the loss of many red blood cells, oxygen is not distributed through the body, which causes Ordinary Cells to start dying of asphyxia, turning the dying body into a cold and desolate landscape. It gets so bad that, had it not been for the transfused red blood cells, AE3803 (and the rest of the other cells) would have ended up dying.
• A Day in the Limelight: During the Lactic Acid Bacteria Arc (Volume 5), Ordinary Cell replaces Red Blood Cell as The Watson as he accompanies Neutrophil in returning the lactic acid bacteria to their proper homes.
• Deadpan Door Shut: Played for Laughs. AE3803 is a rookie red blood cell with absolutely No Sense of Direction, and working in a place as complex as the human body is only natural that she gets lost and enters places she shouldn't. On one such occasion, she ends up in the alveolar complex where a hostile bacterium is lurking. She knocks and then opens the door of an alveolar sack hoping to ask for directions. She and the bacterium tensely stare at each other and, after a Beat, she closes the door. The bacterium then burst out of the wall yelling that "don't pretend anything happened!".
• Deliberate Values Dissonance: Despite the fact that they're usually just as sentient as the body's cells, nothing resembling civilized justice is shown to any of the body's pathogens; the one and only option is for them to be killed on sight. Obviously, this is done to follow real-life biology, and given that it's well understood how much real-life destruction and death these germs inevitably cause when allowed to live, it's very difficult to feel any pity for them. This is one of the big reasons why Cancer Cell is such a tragic villain - despite never actually doing anything wrong, he was treated like a monster from the moment he was born because of a mistake his progenitor made. It would be incredibly inhumane if not for the fact that he can and will kill everyone else in the known world if he's allowed to continue existing.
• Demoted to Extra: Epithelial cells are presented as environment instead of as people, despite being every bit as alive as the blood cells. This is most likely done to simplify matters, and to remove the potential issue of having every wall, floor and door the protagonists pass through be composed of people stacked on top of each other.
• Description Cut: In chapter 26, AE3803 assures U-4989 that U-1149 is relaxing and not doing anything stressful. Cut to him hunting down bacteria with a very murderous expression.
• Destructive Savior:
  • A Steroid deployed during a cedar allergy attack managed to suppress the reactions, but at the cost of leveling the rest of the area.
    Cells: I'm sorry, B Cell and Mast Cell! I'm so sorry! You guys... you guys are so much more civilized than that thing!!
  • Standard operating procedure for dealing with virus-infected cells is to outright destroy them. Few cells are particularly comfortable with the fact that their "protectors" would turn on them like that.
• Detect Evil: All Neutrophils have a lollipop-shaped signal hooked to the back of their hats that emerges when invasive entities such as bacteria are nearby.
• Deus ex Machina: A Justified Trope - many common medical procedures would certainly look like deii ex machina to the cells inside the body.
  • During the heatstroke chapter, the body was about to collapse from the heat and the blood cells can't defeat a rampaging bacterium. Then, suddenly comes "a flood from the heavens" (actually a fluid infusion) that rehydrates the body and solves everything. This is Lampshaded so heavily it borders on a direct reference, since the secretion center commander resorted to praying for rain out of desperation only moments before, leading to him and his subordinates to wonder if it was actual divine intervention.
  • Just as the body was about to shut down from a hypovolemic shock, the red blood cells are gone, the Ordinary Cells are dying due to lack of food and oxygen, and the bacteria are rampaging in the body... suddenly comes an army of Red Blood Cells from a blood transfusion to get it back in order. It's almost a played straight version of the trope, but not quite, because we see where the new Red Blood Cells come from.
• Didn't Think This Through: When the host is going through hypovolemic shock, the Brain Cells decide to increase blood pressure to get the Red Blood Cells to move faster. The increased pressure ends up blowing many of the cells out of the wound, which the survivors annoyedly lampshade.
• Disease-Prevention Aesop: One chapter has an invading bacterium taunt Neutrophil U-1146 on how to prevent heatstroke, even though the host body already had it. Granted, heatstroke is not a disease, but it is close to this trope.
• Dissonant Serenity: The Macrophages are just as bloodthirsty as their male counterparts, but they tend to hide it under a calm, gentle appearance.
• Diving Save:
  • U-1146 does this to Memory B-Cell, Red Blood Cell and Senpai Red Blood Cell in Episode 5, when they are about to be fired upon by the Steroid.
  • Later in Episode 12, Red Blood Cell's kouhai does this to her when U-1146 kills a pathogen, releasing its blood spray in their direction. She's largely unsuccessful, however, and both end up getting drenched.
• A Dog Named "Dog": All of the various personalities in the series are pretty much known by their cellular name. Luckily, this hasn't caused the setting to be as much of a Planet of Steves as one would think; some of them are identified by the call signs featured on their clothes,^note the main characters we follow are White Blood Cell U-1146 and Red Blood Cell AE-3803, for example while groups of the same cell will have only their most prominent member referred to by species name.
• "Do It Yourself" Theme Tune: The opening theme of the anime, "Mission! Health Comes First" is sung by Kana Hanazawa (Red Blood Cell), Tomoaki Maeno (Neutrophil), Daisuke Ono (Killer T Cell) and Kikuko Inoue (Macrophage). The dub follows suit (a first for an Aniplex release) with Cherami Leigh (Red Blood Cell), Billy Kametz (Neutrophil), Robbie Daymond (Killer T Cell), and Laura Post (Macrophage). This also applies to the second season's opening, "Go! Go! Cell Festa".
• Drill Sergeant Nasty: The squad leader of the Killer T-Cells, who trains his underlings in a harsh way. In "Thymocyte", the Thymic Epithelial Cell drill instructors are similarly harsh to the recruits.
• Droste Image: Red Blood Cell screaming at the sight of an invader sometimes shows a smaller version of herself in her mouth, whose mouth has a smaller version of herself, and so on.
• Dualvertisement: Rather fittingly, with Giant Microbes.
• Due to the Dead: Neutrophils have been shown folding their hands in prayer beside a defeated enemy. In the cedar pollen allergy episode, upon hearing that the pollen is harmless but the immune cells are supposed to kill them anyway, Red Blood Cell also folds her hands in apology.
• Early-Bird Cameo: A few for the anime:
  • Cedar Pollen appears in the opening before its proper debut in episode 5.
  • Before becoming an important character in episodes 6-7 of the anime, Cancer Cell appeared in disguise encountering AE3803 twice in episodes 2 and 3. Akira Ishida is listed in the credits as "Ordinary Cell". He even appears for a split second in the intro!
• Early-Installment Weirdness: The first few chapters contained odd immunological responses like killer T-cells being sent out against bacteria (killer T-cells kill infected human cells, and can't do much against bacterial infections), while neutrophils show up against the flu virus (neutrophils are too small to ingest infected cells). This also makes the White Blood Cells' name an Artifact Title as they are later clarified to be neutrophils. Thanks to the anime adapting chapters out of order, it reduces the weirdness by introducing the immune response gradually.
• Eating the Enemy: Phagocytes eat pathogens to identify what they are. Here, most of the cells that engage in phagocytosis eat the germs cooked, while Neutrophils munch on them on the spot, a likely allusion to real life neutrophils devouring pathogens a lot faster than other phagocytes such as macrophages.
• Eat Me: U-1146 disposes of the lead Vibrio bacterium by goading the germ to eat him and then cutting his way out.
• Economy Cast: Despite there being trillions of cells in the human body, each prominent recurring cell is more or less functionally representative of their entire cell type. For example, while there is an entire squadron of Killer-T cells, it's their squad leader who plays the largest role, and while there are ostensibly several macrophages, only one frequently makes an appearance.
• Edutainment Show: While it is a fun story, it teaches readers about the basic functions of cells and microorganisms in the body along the way.
• Eldritch Location: The "Outside", which is where all of the viruses and bacteria are coming in from, and which also serves as a Death World for the cells if they ever happen to fall out into it from their world.
• Elite Zombie: At the end of the Influenza chapter, Influenza-A has whip-like tentacles for arms. Due to the Effector-T Cells Crippling Overspecialization, they can't so much as lay a finger on them. In the anime, Flu-A simply strikes bodybuilder poses instead, presumably to save on the budget.
• Embarrassing Old Photo:
  • Weaponized. Dendritic Cell's ability to activate Naive T Cells is depicted as him showing old photos of the rest of the squadron, which in turn reassures the Naive T he's talking to and allows him to join the fight as a musclebound Effector T Cell. We soon get a shot of the other T cells getting "agitated" (depicted as sudden chills) from sensing this taking place.
  • A later arc also plays on the "agitation" angle by having him tossing a whole box of photos into a crowd. The cells get so embarrassed they basically go into overdrive, combating the oncoming threat.
• Episode of the Dead: The Influenza chapter/episode depicts the Influenza virus infecting bodily cells as a Zombie Apocalypse, where cells have the virus latching onto their heads and giving them a zombie complexion. The cells of the immune system from the Neutrophils and Cytotoxic T-Cells all fight against the infection, before Naive T-Cell who possesses the antigen specifically against this strain of Influenza, gets activated into an Effector T-Cell and lays waste to the Influenza army.
• Everybody Cries: All the erythroblasts at their graduating ceremony in the bone marrow do this.
• Expospeak Gag: Basophil's speeches are riddled with confusing metaphors, some of which vaguely references events currently happening or about to happen. During the food poisoning plot, he says, "a raging torrent of hellfire will force open the forbidden door", i.e. the host will vomit.
• Eye Scream: A young AE3803 is cornered by a Pseudomonas bacterium. Recalling her determination to become a full-grown Red Blood Cell, she flings her hat in a desperation move, hitting the bacterium in the eye. He screams in pain, and she has time to run past.
• Face Doodling: Among the cytokines (embarrassing photos) Dendritic Cell uses to activate the immune cells is one of a sleeping Memory Cell with a giant unibrow drawn on his forehead.
• Failed Attempt at Drama: In the allergy episode, Memory B Cell begins delivering an ominous prophecy to Red Blood Cell and Neutrophil... but realizes he forgot it. He wordlessly rushes away, retrieves his notebook, and returns, panting. Then he describes the prophecy in the same ominous tone.
• False Innocence Trick: A bored Ordinary Cell makes fast friends with a possessed cell, thinking it to be a harmless prankster. This quickly turns on its head when the cell tries to kill the poor boy after goading him to try on his "hat".
• Fantastic Caste System: A downplayed example, but what type of cell a given blood cell grows up to be is determined by the Hematopoetic Stem Cells, who apply such designations to the cells at birth.
• Fisher King: Whatever is happening to the body externally reflects in some way on the cells' plane. For example, a person suffering from heat stroke will have that reflected in their world as a massive heat wave.
• Foregone Conclusion: The outcome of half of the infections that happen in the series are fairly easy to guess.
• Foreshadowing:
  • The information box/narration describing a cell's function is slightly different every chapter/episode the cell is first seen, and occasionally, it contains a hint for what is to come. For example, the exposition in the introduction to NK Cell mentions that she attacks cancer cells. Sure enough, their enemy in the following chapters/episodes is a cancer cell that went unrecognized by everyone else.
  • As Cancer Cell lays dying, he says to U-1146 that he admits defeat "for now". He keeps his word come the "Return of Cancer" arc in Volume 5.
• Forgotten First Meeting: Turns out Red Blood Cell and Neutrophill already met each other when they were still an erythroblast and a myelocyte (basically children cells) when a bacterium attacked the bone marrow they were staying in. However, they only met that one time, so they don't remember each other's faces when they meet again as adult cells.
• Funny Background Event:
  • U-4989 is frequently seen... improvising, and taking advantage of the environment alongside using his standard repertoire of knives, such as: A box of Steamed Buns (chapter 15), One of his knives, tied to a pipe, acting as a crude spear (chapter 16), A giant marshmallow rod, seen playing with it after the arrival of the transfused Red Blood Cells (chapter 18), and Acid-resistant enamel cookware armour, to complement his actual weapons (chapter 20).
  • In Chapter 8/Episode 6, U-1146 is having a serious discussion with the disguised Cancer Cell about how some cells are simply fated to die in order to keep the body safe, and the next scene cuts to NK Cell stomping on Killer T Cell on top of a pile of crates, while declaring, "I won".
  • In Chapter 16, while the Ordinary Cells and Mast Cell are making up with each other, AE5100 can be seen berating AE3803 again for being in the center of another incident with U-1146 watching awkwardly.
  • In the beginning of the heat exhaustion chapter, when all the red blood cells are marching, one cell in the foreground is removing his shirt, and the cell next to him is covering her eyes in embarrassment.
  • in the spread with the gut flora, a bacterium in the background is using its spiked limb as a makeshift fishing rod.
• Furry Confusion: The regularity with which Neutrophils get covered in blood, much less Red Blood Cells bleeding, can get rather confusing. Lampshaded when U-1146 quips about a scratch he got during an abrasion event.
• Fusion Dance: In the Staphylococcus aureus's return episode, the bacteria fuse into one giant bacterium to fight the Neutrophils.
• Gendered Outfit:
  • The Red Blood Cells get this, oddly enough. The men all wear pants and a longer jacket, while the girls wear shorts and a cropped jacket.
  • NK Cell wears shorts as part of her uniform. In Cancer Cell's flashback, a male NK Cell makes an appearance, and he's depicted wearing slacks.
• Genius Loci: Well, the "world" the cells are in is inside a human body. All the disasters they're experiencing are actually illnesses or injuries the body is experiencing.
• Gondor Calls for Aid: Staphylococcus Aureus mocks U-1146 for his dedication to the fight when all the other non-combat cells flee and the more threatening defense systems are too far away to help in time. He mocks her back for having overlooked their greatest and most reliable allies... cue the Platelets, easily the least threatening cells in the whole body. Who promptly clot up the abrasion, cutting off Staphylococcus' invasion route and turning the tide of battle in one fell swoop.
• Gratuitous English: There's a bit of English among the Naive T-lymphocyte recruits ("Yes sir!"). The Japanese opening and closing songs also contain some lyrics in English.
• Gravity Screw: When a bump on the head causes internal bleeding, it has the side effect of making all the blood cells float around in the air.
• Guilt-Free Extermination War: The Immune Cells are merciless against foreign invaders, immediately killing anything they recognize as an antigen or germ. Given that they are literal germs with no other aspirations or purpose other than to take over the body or kill the cells for nutrients, there's never a need to feel bad about it - it's something that goes on inside you every second of every day after all. This is one reason why Cancer Cell wants to multiply and take over the body. Since the world wanted him dead, he feels that the other cells should taste what being hunted and killed feels like. However, despite his more sympathetic characterization, his death is still portrayed as entirely necessary.
• Hammy Villain, Serious Hero: White Blood Cell is the main hero and is known to be very stoic and serious. The majority of the Villain of the Week germs he goes up against are cartoonishly evil and hammy.
• Headbutting Heroes: Killer-T and NK cell don't get along and will bicker and fight each other given the chance. NK does this to make sure that the other cells will be safe, but Killer-T will still insist on doing the job.
• Heartbeat Soundtrack: Once the heart (represented as a giant Taoist temple) shows up, the heart beating faster is heard as accelerating drumbeats. Particularly prevalent in episode 12, which deals with life-threatening hemorrhage.
• Here We Go Again!: Chapter 3 of the manga and Episode 3 of the anime, which ends with the immune cells now having to deal with Influenza A, that not even that Effector T-Cell and his progeny were able to take down, as effector T-cells are antigen-specific. Ouch!
• Heroic Comedic Sociopath: The Neutrophils are practically insane when they encounter a harmful bacteria or any harmful foreign body that enters the body. It wouldn't be inaccurate to say they take their job way too seriously.
• Idiosyncratic Wipes: The anime uses piles of the same hats as the "edge" of a wipe for scene transitions.
• Inherent in the System:
  • Allergies are portrayed this way. Everybody did their jobs exactly the way they were supposed to and it turned into a disaster anyway.
  • The Return of Cancer arc shows the same problem as concerning Regulatory T Cell having a tendency of defending cancerous cells due to still having some similarities to the rest of the cells in the body (i.e. their white t-shirt that reads cell). The only reason they were able to wipe it out quickly the first time is that they got to it first.
• Inn of No Return: The Peyer's Patch appears as a bar/larder filled with food where the Campylobacter can stay in for generations. In reality, it's a death trap for the invaders: the place is a set, and immune cells are wearing baskets, crates, and barstools over their heads or hidden behind panels in the wall. It's safe to assume that with the dozens of immune cells present, the bacteria aren't coming out alive.
• Interservice Rivalry: The Killer T Squad Leader doesn't get along with either Helper T Cell or NK Cell and is rather dismissive of immune cells who fraternize with other cells, especially U-1146 when he's hanging out with AE-3803.
• ISO-Standard Urban Groceries: A variation. The food baskets that Red Blood Cells occasionally carry (which represent nutrients—see Artistic License – Biology, above) always contain one or two baguette sandwiches, and occasionally, apples and oranges.
• It's a Small World, After All: Out of trillions of cells in the large body, the main cast always manages to bump into each other whenever the plot happens.
• "Jaws" First-Person Perspective: In the heat stroke arc, after the body is rehydrated, there's a POV shot of U-1146 swimming towards the Bacillus cereus, just as the latter realizes he's in big trouble.
• Kaiju: The Anisakis worm, depicted as a whale/eel monster.
• Killer Robot: The steroid is depicted as a Cyber Cyclops with a Wave-Motion Gun for its eye which indiscriminately destroys anything in its path regardless of friend or foe until it runs out of power.
• Last Stand: In the Influenza arc the T Cells, Neutrophils, and Macrophage are cornered and outnumbered by virus-infected cells, but they're prepared to fight. Fortunately, Effector T Cell arrives and turns the tides.
• Limited Wardrobe: Kinda justified, every cell wears a uniform corresponding showing what kind of cell they are. It's shown in an omake that they change clothes when it's damaged, which is a way to represent how cells are replaced in real life. Red Blood Cells also wears a reversible jacket that they switch depending if the cargo is oxygen or carbon dioxide.
• Ludicrous Gibs: The fate of pretty much any bacteria or other threat who crosses paths with Neutrophils. Expect lots of blood/cytoplasm.
• Mass "Oh, Crap!": Happens rather often. Especially notable when the steroid bot goes on a rampage in episode 5.
• Meaningful Appearance:
  • Unlike the nondescript caps worn by most blood cells, Red Blood Cells wear puffy red hats that are based on how real-life red blood cells are shaped.
  • Erythroblasts wear similar hats, but contain a pom-pom at the top that symbolizes their nuclei.
• Meat Moss: Large concentrations of cancer cells (tumors) resemble this, crawling all over the walls and ceilings of their cell membranes, a continuous mass of malformed limbs, moving faces, and teeth.
• Mercy Kill: In the HIV special chapter, the story focuses on a different Helper T commander and the Killer T squad leader in a different body, who were best friends back in Thymus School. An HIV invades the human body and infects most of the Helper T cells, including the commander, turning them into mindless zombies that can't deploy the Killer T cells to help out the other cells battling against the invading mold. However, with the help of anti-HIV medicines, the Killer T squad leader captures the infected Helper T cells and gives the main Helper T commander a chance to release the Killer T cells under an emergency command to take down the molds. But when the Killer T squad leader is checking on his friend, he too is infected by the HIV and begins to attack him, when he regains control for a few seconds, the Helper T commander allows his good friend the Killer T squad leader to finish him off.
• Me's a Crowd: Bacteria like the Pneumococcus can divide themselves to gain larger numbers. As can most cells, such as when Former Naive T-Cell returns as a whole army.
• Missing Child: In the Flashback Episode, a child-cell gets lost during a training exercise and cornered by whom she assumes is her teacher. Another child-cell tries to save her, only to get hurt because he lacks the experience to fight back. It's genuinely harrowing until the White Blood Cell Instructor pulls off a Big Damn Heroes and saves hem both.
• Monster of the Week:
  • For the most part, the series follows a simple plot of random harmful pathogens invading the body and causing havoc until the cells of the immune system defeat them in one way or another. Justified, since that is what actually happens in the body everytime, and that way, the manga can show the different germs that menace the body, the cells who fight them and how the immune system works. The only notable exceptions in the first four volumes are the episodes of the Cancer Cell and the hypovolemic shock, that last two chapters for each one and feature threats that nearly kill or seriously harm the body.
  • Volume 5 is an exception to this, since, except for the first chapter, that has a Helicobacter pylori as the monster of the week, it follows a cohesive plot of U-1146 and Ordinary Cell trying to find a home for the lactic acid bacteria, mixed with a new influenza outbreak, an invasion of harmful bacteria in the intestines and another confrontation with Cancer Cell.
• Monstrous Germs: The bacteria are depicted as evil aliens that wouldn't look out of place in Dragon Ball.
• Mood Whiplash: Episodes 12 and 13 feature Scenery Gorn in the episodes proper and the episode preview/recap, with the lighthearted ending/opening sequence in between.
• Mook Horror Show: The season 1 anime opening has an army of Neutrophils chasing down a cute pollen allergen that stumbles without care. The show proper reveals that the allergens themselves are harmless, but the body's programming sees them as a threat.
• Mountain of Bodies:
  • The blood clots are depicted as a mountain of blood cells caught in a huge fibrin net patched over another net which covers a giant sinkhole. Thankfully, unlike in real life, they are not actually killed and simply rendered very uncomfortable for a few days.
  • A darker example happens in the pimple chapter, where U-1146 stumbles upon a mountain of corpses of his fellow Neutrophils, aka pus.
• Mr. Exposition: Neutrophil U-1146 is usually the one who explains cell functions to Red Blood Cell (and the audience), but in episodes where other cells receive focus, the role goes to other cell instructors — for example, Thymic Epithelial Cell explains thymocyte development in "Thymocyte".
• Mundane Made Awesome: A major point of the show is showing how often-mundane events in and around the body are perceived when on a cellular level. For starters, sneezing is portrayed as a missile launch and a scrape on the skin is a giant sinkhole. Allergies are portrayed as an apocalyptic event, with a great flood^note actually Mast Cell overproducing histamine, eruptions^note caused by sneezing missiles and earthquakes^note nasal inflammation happening before a steroid was able to stop them a la The Terminator.
• Mythology Gag: The anime's opening shows U-1146 carrying the Platelet Leader while he's about to attack, just like he does on the manga's third volume cover.◊

N-Z

• Neutrality Backlash: The opportunistic bacteria are largely a bunch of fair-weather friends who side with whoever has the upper hand and will switch in a moment's notice. Because of this, they don't get much respect in return; the harmful bacteria consider them a bunch of suck-ups who can't be relied on, while the neutrophils would rather just kill them off even if they're friendly - they're still germs, after all.
• Never Bare Headed: Except for one scene during the Cedar Allergy episode and most of the Heatstroke episode, every single Red Blood Cell and most immune cells are almost never seen without a hat that depicts the kind of cell they are.
• Non-Standard Character Design: The Neutrophils look out of place when compared to other cells in the body. Their chalky white complexion, Creepy Shadowed Undereyes with pitch-black eyes puts them into near uncanny valley levels. Plus they don't have any eyebrows!
• Oh, My Gods!: Starting here and maintained in the spinoffs, whenever the cells are confused or disturbed by various events, they end up exclaiming "what the cell?" instead of "what the hell?", since the cells have no concept of an afterlife and it makes for a good pun.
• One-Gender Race:
  • Most types of cells when appearing in multitudes are depicted in only one gender. Exceptions are Red Blood Cells and Platelets, which are depicted as both male and female. Justified for the all-male Ordinary Cells, as they're all just self-made clones of each other.
  • In "Thymocytes", both boys and girls are seen training in the thymus during a flashback. However, in the present, only male Killer T cells are shown, Helper T cells have only ever been represented by one male character, and Regulatory T cells have only been represented by one female character. Therefore, it's not clear if female Killer and Helper T cells exist and we simply haven't seen them, or if the female T cells seen training were all training to be Regulatory.
  • In Cancer Cell's flashback, we briefly see what appears to be a male Natural Killer Cell, making them another exception.
  • In Chapter 27 of the manga, U-1146 believed that his male band cell senpai, later revealed to be Basophil, was Eosinophilic after failing to find his name among the Neutrophilic band cell record. The fact that he thought to do so seems to suggest that male Eosinophils also exist.
• One-Man Army: U-1146 is portrayed this way, surviving bacterial attacks that should have killed neutrophils in real life. An example of this is defeating the Acne King by himself when many of his comrades were killed. Sure he gets help from the hair cells but that's still pushing it...
• Opening Narration: Each episode starts with the following from The Narrator:
  Inside the human body, roughly 37.2 trillion cells work energetically, 24 hours and 365 days. They are all working very hard. This is the inside of a human body.
• Orphanage of Love: How the red bone marrow is depicted, with immature blood cells of all stripes being lovingly tended by macrophages and white blood cells.
• Our Zombies Are Different: Viruses such as Influenza and Rhinovirus can turn ordinary cells to zombie-like creatures by attaching itself to a host head. Said host can spread spores that can affect other cells. Combined this with its speed and ability to antigen-shift, these viruses are a pain to contain and kill.
• Papa Wolf: In the Flashback Episode, the White Blood Cell instructor moved to save a younger U-1146 and AE3803 on realizing a giant germ was threatening them in the bone marrow. He then took time to check over his protege, relieved neither of them were hurt. Not too badly at least; U-1146 tried to fight the germ but was curbstomped.
• Parasite Zombie: Viruses manifest as a hat or a mask that controls a cell's mind.
• People Jars: The regular cells are in charge of creating clones of themselves using machines with fluid-filled tanks, where the clones float before they're ready to emerge.
• Pipe Pain: In chapter 16, U-4989 is seen wielding a pipe, with one of his knives tied to the end by some cloth.
• Pokémon Speak:
  • The Lactic Acid Bacteria all can only speak "Nyuu". It's derived from nyuusankin, the Japanese term for them.
  • The Cedar Pollen Allergen all can only speak "Cedaaar".
  • The dengue-infected Langerhans Cells can only say "deng".
• Pragmatic Adaptation: The anime adapted the manga chapters out of order to fix some issues on how some immune cells are portrayed. It is also done to focus on introducing characters one by one and as a way to make a character arc for AE3803.
• Production Throwback: Though Effector T's JoJo-like transformation was already in the manga, it gave David Production (the studio that produces the franchise's 2010s adaptations) a good excuse to bring out their house style for the occasion.
• Prophecies Are Always Right: The Memory B Cell is always going on about "prophecies" of pathogen attacks recorded by his predecessors, which represents how memory B cells produce antibodies based on pathogens the body has encountered.
• Prophecy Twist: Legends passed down between Memory Cells tend to have this effect. One such legend involved the ground splitting, floods, and volcanoes erupting when the body had an allergic reaction to cedar pollen. All of these happened, but slightly different: The eruptions were sneeze missiles, the land rising was the inflammation of the nasal mucosa, and the floods were the overproduction of histamines and tears.
• Puppeteer Parasite: Most viruses are depicted similarly to headcrabs: a funny hat with a Lamprey Mouth on the underside. Once they attach to a cell, the cell becomes a zombie performing the virus's whims.
• Real Life Writes the Plot: The final volume encompasses a struggle with COVID-19 outbreak, while the world faced this virus in a pandemic. Fittingly, it's the final enemy faced in the series.
• Regional Riff: Journeys to the heart will always be associated with drums and occasionally bells in the anime, as they represent the heartbeat. Elaborated in Heartbeat Soundtrack above.
• Reverse Grip: All neutrophils hold their knives this way. The Killer T squad leader also holds his knife this way when needed.
• Rewatch Bonus: N.K. asks a cell that she saved from infection to show her where he was attacked. She also holds him in a headlock, as contrasted when Killer T asks for the cell's arm. She knew it was a disguised Cancer cell and was treating him as a threat.
• Running Gag:
  • Red Blood Cell freaking out and responding with The Scream whenever she encounters a harmful invader or gets berated by other cells.
  • U-4989 and his various improvised upgrades, arms, and armour. See Funny Background Event for a list.
• Scenery Gorn: After the steroid has indiscriminately fired at cells and buildings alike to halt the allergic reaction, the ruins of the town makes up the final shot of the episode/chapter, showing how much damage was done by the immune cells and then the steroid.
• Schmuck Bait: In order to trick some invading intestine bacteria, an epithelial held hostage by them seemingly gives them what they want by leading them to a pocket of the stomach with food stores. They actually lead them to a Peyer's Patch, which gives various immune cells a convenient place to gather up all the offending bacteria in order to kill them all in one place.
• Self-Fulfilling Prophecy: Memory Cell's prophecy did happen thanks to the overproduction of histamine that Mast Cell produced and the emergency immune system kicking in. U-1146 acknowledged this trope, saying that even if the flood didn't happen everyone still has to do their jobs so the outcome would be the same.
• Share Phrase: "Thank you for your hard work!" - said by cells to other cell types for doing their jobs well.
• Ship Tease: For whatever reason, despite being cells, belonging to the same body, etc., U-1146 and AE-3803 have romance tinged interactions. For example, in the beginning of Episode 4, U-1146 and AE3803 were at the stomach's observation deck... as if they are having a date.
• Single-Stroke Battle: How the Neutrophils are depicted in killing off bacteria and viruses.
• Shooting Gallery: The Boot Camp Episode features thymocytes (developing T cells) going through a training exercise where they have to identify and attack cut-outs of Ordinary Cells that have become cancerous or been infected by a virus.
• Shout-Out:
  • Effector T Cell is a parody of various heroes in JoJo's Bizarre Adventure. In the anime, he even uses Jotaro's famous "ORAORAORA!" yell. Ironically, his voice actor was only the minor villain Santana, though the dub's better in this regard by casting Avdol's actor Chris Tergliafera.
    • The tengu mask attaching itself to the Langerhans resembles the way Stone Masks attach themselves to people.
  • Also, the way Eosinophil kills the Anisakis worm, depicted as a white, whale-like monster, by leaping onto it and spearing it, may as well have had her say "from hell's heart I stab at thee!"
  • Cancer Cell strongly resembles Ken Kaneki with his white hair, mismatched blackened eyes, and Lovecraftian Superpower of producing additional appendages from his body. The cancerous extensions could also be a reference to The Thing (1982).
  • In episode 5 of the anime's second season, U-2048 shouts "UNIVERSE!" after declaring an embarrassing photo of himself from when he was younger to be Old Shame.
• Shown Their Work:
  • The cells' different personalities, uniforms, and habits all come from some aspect of the cell they were based on. For example, the part about a pneumococcus hiding in Red Blood Cell's carton in the first chapter / episode? An academic paper less than a year before it was published.
  • While showing the bacteria as creepy aliens, there are some references to their actual morphology, such as Staphylococcus Aureus having a dress shaped like a grape cluster, or the gram-positive Pneumococcus being purple.
  • Dr Hope's Sick Notes, a Youtube channel where a real doctor reviews depictions of medicine in shows, absolutely loves the show for this, and will routinely pause it and explain in more detail how something works and how they got it right.
  • Cancer cells are able to hide from immune cells by masquerading as Ordinary Cells until antibodies signal them as targets. But they also can fight back against them and all of that is biologically accurate. First, they stockpile resources and slowly but surely change a tissue's structure so it's easier for them to do cell division at extremely high rates. All of that while they give the same chemical signals healthy cells do. When immune cells start detecting them because all of that abnormal activity starts releasing its own warning, chemical signals, cancer cells take on the offensive. They are able to deactivate some immune cells, especially NK and T-cells. When approaching metastasis, they can even signal them into apoptosis (cell suicide). That's why is so hard for the immune system to fight off cancer.
• Sliding Scale of Silliness vs. Seriousness: Definitely on the sillier side of things with a dash of violence. Gradually, the manga is not afraid to show off some deadly consequences on the human body such as Heat Stress, Hypovolemic Shock, Dengue and Cancer and how the immune system responds to said dangers. The first two example even imply that the human body was hospitalized and given medical aid.
• Snow Means Death: The hypovolemic shock chapter portrays body shutdown as a freak blizzard, which most of the blood cells fall unconscious in.
• Soundtrack Dissonance: The cedar pollen allergy episode shows what happens when immune cells have an inappropriate reaction to something normally considered harmless, with ominous music playing throughout the events. However, once the steroid arrives to its destination and is identified as such, grand, upbeat classical music plays as the steroid devastates the town by shooting at cells and buildings.
• Spanner in the Works: After being defeated the first time, Cancer Cell returns, tricks Regulatory T cell into protecting him, and starts absorbing toxins produced by harmful gut flora to empower himself, becoming nearly invincible. However, because Ordinary Cell picked up the stray Lactic Acid Bacteria and helped them get back to the intestines, the harmful bacteria are swiftly beaten and Cancer Cell gets weakened enough that he loses the upper hand in the battle with the immune cells and is ultimately killed.
• Stealth Escort Mission: AE3803 decides that she's going to stop being such a burden to others due to her No Sense of Direction (a liability when blood cells are anthropomorphized as oxygen deliverymen). In order to encourage her, U-1146 discreetly follows along to pick up after her (throwing her directions notebook and hat back when she loses them in a crowd), make sure she stays on track (realigning a road sign so she sees it) or protect her from harm (sneaking up on and eliminating a pair of bacteria lying in ambush). He is easily spotted by other red blood cells, which gets him dirty looks as they think he's a stalker.
• Stealth Pun: Sneezing is depicted as a high-powered missile carrying junk and unwanted materials — a literal "snot rocket", if you will.
• Straw Civilian: Downplayed. Ordinary Cells and Red Blood Cells other than AE 3803 tend to fall into this, calling the fervent passion that Neutrophils and other members of the immune system have towards killing pathogens creepy, but know full well not to get in the way.
• Super-Persistent Predator: Neutrophils will actively chase off foreign enemies and follow them until they are killed, even at great risk to their own lives.
• Suspiciously Specific Denial: Killer-T definitely doesn't daydream about being on friendly enough terms to play cards with the other cells.
• Sweet Tooth: All Red Blood Cells are shown as being fond of ice cream. Justified, as "ice cream" in the body is actually glucose/dextrose, which red blood cells rely on as their sole energy source.
• Tears of Joy:
  • After her platelets successfully mend a hemorrhage, Megakaryocyte cries happy tears as she lavishes them with praise and rewards.
  • U-4989 is moved to tears when AE3803 says white blood cells are super reliable.
• Teeth-Clenched Teamwork: NK Cell and Killer-T can't just get along and will bicker no matter who they're facing. Killer-T even lampshades that they have no compatibility whatsoever.
• Tempting Fate: In "Monocyte", Red Blood Cell tells her senpai that she's never heard of a blood cell who only seems to run into trouble. Gilligan Cut to her fleeing in terror from a bacterium.
• Theme Tune: "Mission! Health Comes First!" goes for a more traditional variant than most anime opening themes, as it's sung by four of the characters' voice actors and the lyrics are a basic description of the characters' jobs and the premise of the series itself. The first verse (sung by AE3803 and U-1146) is generally used, but the anime will use the second verse (sung by Killer-T and Macrophage) on occasion, such as during the former's day in the limelight in Episode 9.
• They Look Just Like Everyone Else!: The original Cancer Cell is on an advanced stage that allows him to disguise himself as an Ordinary Cell, even managing to fool both U-1146 and Killer-T. Only NK Cell is able to sniff him out thanks to her ability to sense cancer cells. He even managed to fool Regulatory T-Cell into thinking he is an Ordinary Cell, hindering both NK and Killer-T from killing him.
• This Is Gonna Suck: After a week of the body fighting off Influenza B, Influenza A shows up, and everyone has to start the immune response process all over again. Nobody's looking forward to it.
• This Looks Like a Job for Aquaman: Naturally, the chapter that introduces Eosinophil culminates with a fight against a parasite, allowing her to show off her true skill.
• Thousand-Yard Stare: The neutrophils sport these whenever they're fighting, emphasizing their serious, combative nature. Played for Laughs in episode 5, in which everyone sported this after the Steroid Bot's rampage.
• The Topic of Cancer: Both of Cancer Cell's appearances are most decidedly not played for as many laughs as the rest of the show. Both the potential magnitude of his desired effect on the body as well as his tragic backstory are played decidedly straight.
• Torches and Pitchforks: Happens a few times whenever a crisis happens thanks to a character's shenanigans. Mast Cell, B Cell and Memory Cell had been victims of this.
• Tractor Beam: The mosquito taking blood is presented as a set of knives that cut a hole in the ceiling and then pull all the red blood cells in the vicinity upward out of the body. One of them mentions they're inexplicably drowsy as they're being abducted.
• Trademark Favorite Food: To a degree. Nutrients for different kind of cells are represented differently.
  • Red Blood Cells are only able to consume glucose, which is represented as ice cream.
  • Neutrophils eat pathogens they kill, including a processed version that appears to be based on instant noodle cups. U-1146 in particular is often seen drinking (or trying to drink) tea.
• Tragic Villain: The Cancer cells are mutated, dangerous beings, but although they pose a threat to the body they just want to live a normal life like any other cell. After one gets pursued and figures out they're supposed to die, he goes berserk and decides to take the whole body down with him if he isn't allowed to live.
• Training from Hell: Thymocytes endure a harsh training regimen before becoming Naive Cells then later into fully matured T Cells. It is stated that, just like in real life, only 2-3% of the cells pass to become Naive Cells.
• Triple Take: The prolonged moments all involve U-1146:
  • When AE3803 accidentally hit him with the steroid bot container in episode 5.
  • When Killer-T punched him in the face after he admits wanting to be friends with the Red Blood Cells.
• Unlucky Everyman: The body the cells live in is one. They suffer all sorts of afflictions ranging from mild problems like flu or allergies to far more serious problems like dengue fever, hypovolemic shock, heat stroke, and critical dehydration. Of course, if they didn't go through all of this, we wouldn't have a story.
• Uterine Replicator: How cellular division is portrayed. Tissue cells have a cloning vat in their living rooms, and stem cells work at a cloning facility, producing babies from a grey capsule.
• Vague Age: Given that the cast is made up of personified human blood cells, which have a huge disparity of lifespans ranging from a few hours to several months in real life, this shouldn't be surprising. To prevent unnecessary horror, cell death and replacement is represented by characters going home and changing their clothes, but even then the characters still don't seem to age at the same relative rate - we've seen the same Macrophage from the time Red Blood Cell was a child up until now, Dendritic Cell seems to have many generations of T Cell photographs under his belt, and neither of them appear to have aged a day. To make things even more confusing, once a cell has reached maturity it appears to stop physically aging, leaving them as permanent young adults or, in the case of the platelets, small children.
• Viewers Are Goldfish: Every single chapter/episode, a description of a cell's function pops up whenever a character appears, even our main characters.
• Vile Villain, Saccharine Show: The anime is a very lighthearted story about the functions of the immune system sprinkled with little bits of violence. While the pathogens are all varying degrees of nasty and do pose a threat, their villainy is highly exaggerated and comical and under the right circumstances, all get taken down quite easily. Cancer Cell Breaks this format, being a thoroughly-ruthless Knight of Cerebus that relishes in the thought of killing innocent cells, has an actual Freudian Excuse toward doing so, and can give our heroes such a brutal ass-kicking that an entire army's worth of backup needs to be called in before he can be stopped. This makes Cancer Cell feel out of place to the point that one can think he came from another show.
• Villain Respect: Cancer Cell respects U-1146 when he saved him from a rogue cell^note actually a trap that cancer cell devised, offering to hear his last words and learning he views Cancer Cell as a cell struck with misfortune rather than an invader. So much so that he takes his defeat by the latter gracefully and tries not to fight him in the Return of Cancer Cell arc, even offering him a chance to join his crusade of destroying the body.
• The Virus: Well, the viruses. They're depicted as accessories like hats or masks that forcibly attach themselves to cells and brainwash the victims. The victims then create more of these hats/masks.
• Visual Pun:
  • The Dengue virus is depicted as Tengu masks; "dengue" is pronounced very similarly to "tengu" in Japanese.
  • Similarly, the chemical purine is depicted as stacks of puddings (purin is Japanese for pudding).
  • Macrophages holding up wooden cut-outs of Virus infected cells and regular cells for Naive T-Cells during training, as they're antigen presenting cells.
• What You Are in the Dark: In a Flashback Episode, it's revealed that U-1146 rescued AE 3803 when they were still in training...rather, he tried to fight a giant germ that was trying to eat her, with a toy knife, and got his butt kicked for obvious reasons. The germ offered to spare him if he gave up the tiny AE 3803. U-1146 instantly refuses; even if no one would know, it's his job to protect other cells.
• White Shirt of Death: Neutrophils and macrophages are clad in white (neutrophils are chalky-white on top of that), which makes all the blood they get while slashing and stabbing enemies to death stand out more.
• Whole Episode Flashback:
  • AE 3803 thinks back to her childhood in the bone marrow on a delivery run there.
  • One chapter focuses on the past between Killer T and Helper T during their time in the thymus, which is depicted as a military academy.
• Wingding Eyes: Each time when an enemy dies, their eyes often have X's on them. This would result in a Mood Whiplash in which after Cancer Cell dies, his eyes turn into X's after a dramatic conversation between him and U-4989.
• Worf Effect: The Effector T Cell in the Influenza episode had no trouble beating up Influenza B-infected cells, but when a different strain of influenza comes along, he's no match for it.
• Worf Had the Flu: U-1146 had a hard time fighting a single Bacillus cereus due to suffering from heat stress. Once the host body is rehydrated, however, he kills the bacterium easily.
• The World Is Always Doomed: The show takes place inside a human body and it's dealing with infections and ailments on a constant basis.
• You Are Number 6: Because there are so many Red Blood Cells and Neutrophils, they are all given an alphanumerical designation code that serves as their name.
• Your Approval Fills Me with Shame: Cancer Cell considers U-1146 a friend, claiming that they aren't so different. His final words in the Return of Cancer arc are that he's glad that his death is at the hands of a friend. U-1146 disagrees and is unnerved by Cancer Cell's parting words.
• Zerg Rush: The invading bacteria attempted this in episode 2. It failed thanks to the Platelets sealing off the wound.
• Zombie Apocalypse: An influenza outbreak is portrayed this way, with the infected cells becoming zombie-like. Common colds are also portrayed this way, the only difference is that the infected cells seems to have a sense of self.

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