STUDIES ON PLATELET-ASSOCIATED IMMUNOGLOBULINS

Abstract

The amounts of platelet-associated immunoglobulins (PAIgG, PAIgA, PAIgM) and complement (PAC 3) were determined in patients with various types of thrombocytopenia including, idiopathic thrombocytopenic purpura (ITP). The mean amounts of PAIgG, PAIgA, PAIgM and PAC 3 were increased not only in patients with immune thrombocytopenia, but also in those with other types of thrombocytopenia. The percentage of patients with normal amounts of PAIgG, PAIgM, and PAC 3 was significantly lower among those with ITP than those with systemic lupus erythematosus, lymphoproliferative disorders or liver cirrhosis. In ITP, the mean peripheral blood platelet count (p <0.05) and platelet life-span (p<0.01) were significantly lower in patients with simultaneously increased amounts only of PAIgG, PAIgM and PAC 3 than in those with an increased amount only of PAIgG. In patients with ITP, the amounts of PAIgG, PAIgM and PAC 3 were decreased in those whose peripheral platelet count tended to increase after prednisolone treatment. These findings were useful for evaluating the efficacy of prednisolone. In patients receiving multiple platelet transfusion, the amounts of PAIgG, PAIgM, PAIgA and PAC 3 were significantly higher than normal, when peripheral platelet counts remained lower than 100 × 109/L after the transfusion. Moreover, the PAIgG level showed a tendency to be high in proportion to the amount of platelet transfusions.Using SDS-PAGE and Western immunoblotting, the target antigens of blood platelets against anti-platelet serum antibodies were investigated in patients with idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE) with thrombocytopenia, and multiple platelet-transfusion. No clear differences were found in the distribution pattern of various bands, obtained by immunoblotting among the individual disease groups, and several bands were observed in many patients. Under non-reducing conditions, antibodies reacting to antigens corresponding to GPIb (Band-1) and GPIIb/IIIa (Band-2) were found to be nearly the same in the bands of the ITP, SLE and platelet-transfused groups. No clear differences were found in the distribution of various target platelet antigens reacting to anti-platelet serum antibodies among these groups. The same results were observed under reducing conditions. These findings suggest that no differences exist in the type or distribution pattern of target platelet antigens reacting to anti-platelet serum antibodies, by means of the immunoblotting method, among the various types of thrombocytopenia studied.