Immune: A Journey Into the Mysterious System That Keeps You Alive

by Philipp Dettmer

What needs to go wrong for your immune system to get so horribly confused? Well, there are a few stages, a few conditions that need to be met: First of all, your MHC molecules actually need to be physically able to bind to your own self-antigen efficiently. This is mostly genetic, and as everything that is etched into our genetic code, bad luck. You can’t choose your parents and you can’t choose your genetic makeup. (At least not yet.) In an earlier chapter we talked about the fact that MHC molecules vary a lot between different individuals and come in a few hundred slightly different shapes. Not all of these shapes are great, just by a whim of nature, some types are pretty good at presenting self-antigen. There is a hereditary risk for autoimmunity that varies between all of us—so while everybody can get autoimmune diseases, chances are higher for some, those with genes that make specific MHC molecule types. But just a genetic predisposition is not enough.