Episode 18

"Cytokines" (サイトカイン) is the eighteenth episode of the Cells at Work! anime.

Synopsis
Normal Cell travels to the intestines with White Blood Cell to reunite the lactic acid bacteria with their friends, but they get separated from one of the bacteria on the way there.

Plot
Without any warning, Natural Killer Cell attacks Normal Cell for insulting U-1146. But the latter defuses the situation. However, one of the lactic acid bacterium falls through a drain. The two cells can only hope that any immune cells that run into it will be able to know that it has no malicious intent.

Luckily, Dendritic Cell rescues the lactic acid bacterium that fell into the storm drain and cares for it.

Just then, the Influenza Virus attacks again. Unlike the previous encounter, the influenza mutates wildly, causing the infected to become significantly stronger to the point that the immune cells can't harm it. Natural Killer falls into despair when she realizes they can't fight this foe, who assembles the infected to generate a powerful tornado. As U-1146 and B Cell try to take her away, a photo lands on Natural Killer, revealing some of her youth when she cosplayed as a maid alongside a Macrophage. She becomes enraged and attacks U-1146 and B Cell for apparently looking at it before charging at the tornado, ripping off a group of infected from it.

Seeing the threat, Dendritic Cell pinches off the horn from the bacterium in his care and gulps down the contents of Polysaccharides, activating him in the process. The activation allows him to produce Cytokines which take on the form of photos of the cells' embarrassing memories in order to motivate them, causing chaos in the streets as the immune cells look at the photos. With the additional motivation (resulting in humorous scenes involving U-2048, U-2001 and Helper T Cell), the immune cells are able to destroy the influenza before it causes additional problems.

After defeating the influenza, Dendritic Cell fishes out the red lactic bacterium's parents from the waterways and returns their child to them as it bids farewell to him and Normal Cell. U-1146 comes in and offers to take the remaining bacterium off him. Normal Cell apologizes for his behavior while an angry Natural Killer storms off. U-1146 grabs some tea and follows Natural Killer to an alleyway, where he tells her about the bacteria she was looking for, telling her that it's friendly. Natural Killer reveals that there has been a leak with a certain cell's data, shocking U-1146 as he realizes who she's talking about; Cancer Cell.

New characters

 * Influenza Virus

Returning characters

 * Normal Cell
 * U-1146
 * Natural Killer Cell
 * Dendritic Cell
 * Lactic Acid Bacteria