Platelet associated immunoglobulins and complement in idiopathic thrombocytopenic purpura.

A double antibody sandwich enzyme linked immunosorbent assay (ELISA) was applied to quantitate platelet associated (PA) immunoglobulins G, A and M and complement factors C3c and C4. Fifteen patients with acute and 29 patients with chronic idiopathic thrombocytopenic purpura (ITP) were studied as well as 35 normal controls. Forty-three out of 44 (98%) patients had elevated platelet associated immunoglobulins. PAIgG was elevated in 95%, PAIgA in 82% and PAIgM in 74% of the patients. PAC3 was increased in 86% and PAC4 in 57% of the patients. There was strong correlation between PAC3 and PAIgG but not between PAC4 and PAIgG in acute ITP. In chronic ITP, however, PAC4 correlated strongly and even better than PAC3 with PAIgG. This strengthens the conjecture that the pathogenesis of ITP in many acute cases differs from that of chronic ITP.