Relationship between autologous¹¹¹In-platelet life span and peripheral platelet concentration. Platelet life span results are compared to peripheral platelet counts in three groups of thrombocytopenic patients: (1) six HIV-infected patients (depicted by large solid circles); (2) 17 patients with thrombocytopenia due to megakaryocytic hypoplasia (identified by open circles); and (3) nine patients with thrombocytopenia due to autoimmune destruction (clinical idiopathic thrombocytopenic purpura, ITP, shown by open squares). Three thrombocytopenic HIV-infected patients demonstrate concentration-dependent shortening of platelet life spans attributable to increased platelet utilization in maintaining platelet hemostatic function. By contrast, two thrombocytopenic HIV patients show shortening of platelet life span that is greater than expected on the basis of peripheral platelet counts per se, thereby implicating antiplatelet GPIIIa_49-66Abs in the immune-mediated random destruction of platelets. The markedly shortened platelet life span in the sixth thrombocytopenic HIV-infected patient is also probably attributable to immune destruction, although the above comparison of platelet count to platelet life span does not clearly discriminate between hemostatic utilization versus immune destruction for platelet counts of less than 10,000 μL. The platelet life span data in patients with thrombocytopenia secondary to marrow hypoplasia and idiopathic thrombocytopenia represent results obtained from a prior report.23