Cellular Immunity to Platelets in Idiopathic Thrombocytopenic Purpura

The possibility of cell-mediated immune mechanisms against platelets in idiopathic thrombocytopenic purpura (ITP) was suggested in a previous observation. Therefore, the uptake of labeled thymidine by the lymphocytes of 14 patients with ITP and of 16 controls was studied in vitro in the presence of autologous platelets. The control group (normal subjects and patients with nonimmune thrombocytopenia) never demonstrated any sigficant uptake of thymidine in this autologous system. Positive stimulation, as judged by thymidine uptake, occurred in seven of eight patients with severe ITP, whereas only three of six patients with mild ITP showed significant stimulation. Two patients with severe ITP, studied 4 and 6 days after splenectomy, showed a conversion to negativity in the test. These results indicate that cellular immune mechanisms against autologous platelets are present in ITP and suggest that they may play a role in the pathogenesis of the disease. It is suggested that ITP may represent more than one disease.