Antibody against megakaryocytes in idiopathic thrombocytopenic purpura.

Purified human IgG from both serum and the culture of human splenic cells was radiolabeled with 125I. Incubation of radiolabeled IgG from patients with idiopathic thrombocytopenic purpura (ITP) with normal homologous platelets or bone marrow cells resulted in significant (P less than .001) binding when compared with control IgG. Radioautographs showed that the radioactivity was associated with the platelets or megakaryocytes. The antiplatelet antibody in ITP has specificity for antigens associated with both platelets and megakaryocytes and suggests that thrombopolesis may also be affected in this disease.