IMMUNOLOGIC MECHANISMS IN IDIOPATHIC AND NEONATAL THROMBOCYTOPENIC PURPURA

Abstract

Studies on 35 patients with idiopathic thrombocytopenic purpura yielded evidence that an immunologic mechanism is frequently responsible for the low platelet count. Platelet agglutinins were demonstrated in vitro in the plasma of many of these patients. A factor presumably identical to this platelet agglutinin was found to be capable of inducing thrombocytopenic purpura and altering megakaryocytes in normal recipients of this plasma. Remission following splenectomy was not necessarily accompanied by disappearance of the thrombocytopenic factor from the patient''s plasma, a correlation which was seen in spontaneous remissions and those induced by ACTH or cortisone. In the pathogenesis of idiopathic thrombocytopenic purpura the spleen probably serves at least 2 functions:the removal of sensitized platelets, and the production of some of the platelet agglutinin. The lack of evidence for increased platelet destruction in some patients indicated that idiopathic thrombocytopenic purpura probably is a syndrome which may also arise solely from failure of megakaryocytes to produce circulating platelets. In some patients therapeutic failures from splenectomy may result when a high concn. of platelet agglutinins persists after the operation so that rapid destruction continues in the absence of the spleen, and megakaryocytes continue to be affected by the antibody. It seems likely also that the spleen is of less importance in the pathogenesis of the disease when platelet antibodies are not demonstrable. Serologically different platelet types exist. Neonatal thrombocytopenia may develop as a result of transmission across the placenta of maternal autoagglutinins for platelets, or it may be due to development of isoagglutinins because of fetal and maternal platelet incompatibilities.