|MadSci Network: Immunology|
Actually, there is a very important time when new antigens arise in your body: puberty. During puberty, your body produces a whole new range of proteins (which can be antigens) that your own immune system has never seen before. This fact raises an interesting question: why don't people then become autoimmune at puberty?
Well, unfortunately, some people do, but why most people do not remains a mystery. One thought is that these new antigens travel to the thymus, where they can be presented by antigen presenting cells there and participate in deletion of autoreactive thymocytes (so-called central tolerance). Another thought is that when cells first enter the periphery (as the rest of the body is called) they may encounter these neoantigens and be tolerized rather than activated. This could either happen because the antigens are presented in a noninflammatory state (there is no "danger signal" or inflammation going on as a basal state) and so the new T cells are tolerized and/or deleted, or that active suppression of potentially autoreactive T cells occurs.
This is an interesting field of ongoing research in immunology- why are we tolerant? Why do some people lose tolerance to self? I can't wait for the answers to these questions.
Have a great day!
Try the links in the MadSci Library for more information on Immunology.