At the beginning of the 20th century, the knowledge on autoimmunity was very limited. In 1899, Jules Bordet demonstrated that autoantibodies specific for erythrocytes could cause their own destruction in conjunction with serum complement. In 1904, Julius Donath and Karl Landsteiner reported the first observation of a true autoimmune disease, paroxysmal cold hemoglobinuria, a complement-dependent hemolytic anemia. They demonstrated the presence of a lytic substance in the blood of three patients with paroxysmal cold hemoglobinuria. An autoimmune disease can generally be defined as one in which an autoantibody or a sensitized lymphocyte reacts with host tissue. The prevalence of autoimmune diseases is significantly increasing in the world population. We now recognize more than 80 clinically distinct human diseases that result at least in part from an autoimmune response. Autoimmune diseases generally result from the association of genetic susceptibility and environmental triggers. Infectious agents have long been the most well-studied environmental factors. Despite the diversity in natural history and presentation, autoimmune diseases share a number of underlying mechanisms. More selective and less toxic immunosuppressive and immunomodulatory agents are used to treat these disorders, and promising immune tolerance approaches are emerging.
