Another fact that that might lead to autoimmunity are infections that we experience as a result of some type of pathogens. And we'll see what that is in just a moment. Another factor might be damage to immunologically privileged sites and we'll see what that means in just a moment. So let's begin with gene mutations. So earlier we discussed these self antigens and the fact that our immune cells, white blood cells can distinguish between our healthy cells and non healthy cells by these self antigens. And we said the self antigens must be displayed on special protein complexes on the membrane of the healthy cells.