[themafia]

> Then, they get selectively killed if they react to self-antigens. [2]

There's also the ones that react weakly to self antigens and are kept around to put a check on everything else.

https://en.wikipedia.org/wiki/Regulatory_T_cell

The thymus is just insane.

[tialaramex]

Well, Mother Nature doesn't have to make any sense, so that's an advantage to her. This does make our nature - to try to understand - extremely difficult but makes no difference to her either way.