I believe it is lysosomes, because all cells have a cell wall which pretty much limits what goes in and out of the cell as a mitochondria is storage for food and stuff like that. also a nucleus is pretty much the cells brain so all cells have one.
The answer is that they are the building blocks from which proteins are made.
Campylobacter infection
Cryptosporidium infection
Giardia infection
hand, foot and mouth disease
hepatitis A
meningitis (viral)
rotavirus infection
Salmonella infection
Shigella infection
thrush
viral gastroenteritis
worms
Yersinia infection.