Autoimmune diseases are caused by failure to distinguish between host and foreign (e.g. microbial) antigens. We do not know why autoimmune disease occurs and what the relevant pathogenic mechanisms are. Autoantibodies might be considered as diagnostic markers, e.g. as "witnesses" to or "messengers" of autoimmune disease. Therefore, older and newer autoantibodies, as well as results on their respective antigens, will be considered.