for what it's worth, here, the Cell life cycle is metaphorically when we see them switch to clean uniformsAlso binge-watched Cells at Work! yesterday, and man I enjoyed that one. The implications are staggering, though:
Implication #1: We see cells like U-1146 and Killer T bleeding. And U-1146 gets a bruise. And they sweat. Which implies that the cells in this specific body also have fully-functioning circulatory systems and sweat glands. And who knows what else. Which implies that the cells...
...have cells. So somewhere inside U-1146, there's a red blood cell like AE3803 and a white blood cell like U-1146 and so on.
IT'S CELLS ALL THE WAY DOWN! O_O
Implication #2: According to Wikipedia, the average white blood cell lives around 6 days before dying.
U-1146, the white blood cell we see in the first episode, is clearly the same U-1146 we see in the final episode. He's still alive and kicking.
So in less than one week's time, the body they live in experiences:
-Heat stroke bad enough to require intravenous saline
-Head trauma bad enough to require a blood transfusion
To quote a comment from the Crunchyroll comment section, "Dude needs to take better care of himself."