EFFECTS OF ANTIPLATETLET GLYCOPROTEIN IB AND OR IIB IIIA AUTOANTIBODIES ON THE SIZE OF MEGAKARYOCYTES IN PATIENTS WITH IMMUNE THROMBOCYTOPENIA/

To determine whether anti-platelet autoantibodies react with megakaryo cytes, as well as with platelets, in immune thrombocytopenia (ITP), 38 ITP patients were studied. They were classified into four groups; ant i-platelet glycoprotein Ib-positive (group A, n = 5), anti-platelet gl ycoprotein II/b/IIIa-positive (group B, n = 2), positive to both antib odies (group C, n = 3), and negative to both antibodies (group D, n = 28). The number and size of megakaryocytes in each group were compared . The number of megakaryocytes in groups A, B, C, and D was 12.8 +/- 5 .9, 75.2, 29.1, and 17.0 +/- 21.7/mm(2), respectively. The mean cytopl asmic area of megakaryocytes in groups A, B, C, and D was 1001 +/- 26. 3, 1621, 1109, and 1311 +/- 235.6/mu m(2), respectively. This finding indicated that, in the presence of anti-platelet glycoprotein Ib, mega karyocytes were not increased in number and were small in size, wherea s, in the presence of anti-platelet glycoprotein IIb/IIIa, megakaryocy tes were increased in number and in cytoplasmic area. Our study sugges ted that anti-platelet glycoprotein Ib may impair platelet production by megakaryocytes in ITP.