Oh man, that part of the immune system development is probably my favourite. Specifically how in the world the body is able to detect theoretically basically anything that can exist.

This is probably going too deep but you can read a bit on wikipedia if you are interested: https://en.wikipedia.org/wiki/V(D)J_recombination

And to pivot back what you asked, the part where the immune system can detect anything that exists would of course be bad if it detects your own body too, since it attacks what it can detect.

So theres like a training camp for immune cells where they are tested if they can detect your own body’s cells. And if they can, they are killed off. Therefore anything that is left can distinguish between what is good (you) and what is bad (other stuff).

There’s lots of other mechanisms around that though, otherwise allergies or intolerances wouldn’t exist, of course.

All cells are covered in little bumps called antigens. Your body contains antibodies that bind to antigens on foreign cells. Your white blood cells then only attack cells that have antibodies attached to them.

So it’s not about good/bad, but really just about which cells are your own and which are foreign.

It has lots of false positives and false negatives. It is actually a very simplistic system, if it was “smart enough” we wouldn’t have diseases. In fact, a good number of diseases, especially chronic ones that millions or billions of people suffer from throughout their lives, are actually the immune system’s fault. It is not a “smart” system. It is clever. Sometimes. Until it’s not.

I don’t think a dog in heat is a good analogy, seeing as immune cells attack invaders, not try to have reproduce with them. Anyway, others have given good answers.

Your own cells have protein signature directly dependent on the genetics. Everything that doesn’t match is attacked

yes, in fact our moral reasoning comes from the function of white blood cells and their extreme xenophobia - it is an important lesson to learn that foreign = bad, white = good … oh wait, hmmmmmmmmm

They don’t go after everything foreign. They are produced with instructions by which they identify a threat.
It’s their production source which provides the instructions and it’s not that smart or we wouldn’t have cases where the immune system attacks the body itself.