Chronic ITP as a model for immunization by platelets.

In summary, ITP is an autoimmune disorder due to the development of autoantibodies which in the majority of cases are directed against normal platelet membrane glycoproteins. The autoantibody binds to both platelets and megakaryocytes. The binding to platelets can cause phagocytosis by the immune system via an Fc receptor mechanism and in addition can activate the complement pathway which could cause more efficient phagocytosis or in vivo cell lysis. It seems likely that antibody bound to megakaryocytes might influence platelet production as well. At the present time, the immunoregulatory defect which results in this autoimmune disorder is unknown.