The real question: why do some people at some time develop an autoimmune disease, is still unanswered. But we can see the footprints in the snow, and learn a lot from these. Immunohistochemical analyses show us the footprints: they illustrate the situation at a certain time. By looking at different moments in time, we may get a better overall picture, although this technique will still leave us with questions regarding the cause of the footprints.

A frequently occurring autoimmune disease is thyroid autoimmune disease, which often leads to thyroid dysfunction. This disease is considered an autoimmune disease owing to the presence of antibodies and T cell responses directed against thyroid antigens. It is as yet unclear why such immune responses develop, but some predisposing factors have been identified. In the first place, family and twin studies indicate that genetic factors play a part. An association with specific HLA antigens, such as HLA-DR3, has also been found. Since HLA class II antigens have a role in the selection process of the T cell repertoire in the thymus and in the presentation of antigens to T cells, this HLA association suggests that T cells are essential in the development of thyroid …