Why does our immune system have a T-Cell for every Bacteria, Virus, Etc,
In: Biology
It needs some way to store “This is a bad thing, and this is how to kill it.” Without instructions, the immune system just does a bunch of random things all at the same time, causing side effects (which you call “being sick”). With a memory of what to do, the invader is vanquished and you never even know you were exposed to it.
There’s two ways a T Cell learn, basically
Development:
When a T cell is growing it’s exposed to millions of variations of antigens (puzzle pieces) and, as long as the antigen isn’t “self antigen” (self recognizing) it will continue to grow. When it learns the antigen or puzzle piece, it will specifically bind to it, whenever it enters the body
Acquired:
A naive T cell can be presented an antigen / puzzle piece by “antigen presenting cells” or other immune helper cells. Then the T Cell will turn into a killer and seek out any matches
The difference between the protein markers your immune system is looking for and your own cells isn’t all that much. If you want to have an immune system that doesn’t target healthy cells you need a system that can tag exactly which cells are the bad ones. The only way to do that effectively is to have a memory of exactly which cells are good and exactly which ones are bad.
Even with such a complex and specific system in place, autoimmune diseases are still fairly common.
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