The Hygiene Hypothesis

The immune system evolved for host defense, right? Because they're constantly agents that are trying to take advantage of us and so on. Well, if that's true, that we have all these particular types of immune cells, always for host defense as a big army with all the different branches of the military. What happens when there's nothing to fight? They still practice. It's going to be an accurate way. We make millions of millions of neutrophils a day, money and then die, make more; bone marrow is costly working with homeostasis doesn't mean nothing.