[callesgg]

The stronger your immune system is the higher are your chances to survival. Until your immune system is so strong it attacks it’s own host.

Evolutionary pressures will make sure that organisms are very close to the edge between to weak and to strong.

One naive way of interpreting this is that 50% of the population will have a immune response that is to strong (above the edge) and 50% to weak (under the edge). But it is naive to say that, as this is a topic that has much more complexities than the one dimensional model that I have described here.

At what percentage the threshold of the statistics for what we call autoimmune disease would be located would be interesting to know.