Study of platelet-associated immunoglobulins of IgG, IgM, IgA, and IgE classes and platelet kinetics in 33 patients with idiopathic thrombocytopenic purpura.

The role of platelet-associated immunoglobulins (PAIg) of four different immunoglobulin classes--IgM, IgG, IgA, and IgE--and their relation to platelet count and platelet kinetics was studied in 33 patients with idiopathic thrombocytopenic purpura (ITP). During the course of 1 year, repeated determinations of PAIg were made. The results indicate that PAIgG, PAIgM, and PAIgA are present in all ITP patients, and that autoantibodies of all three Ig classes show highly significant correlations to the platelet counts (p < 0.0001). Double logarithmic negative correlations have been found between PAIgG and platelet count (r = -0.71), PAIgM and platelet count (r = -0.84), and PAIgA and platelet count (r = -0.79). Statistical analyses using partial correlation and multiple regression methods showed that PAIgM is predominantly related to the platelet count, whereas PAIgG and PAIgA are only of secondary importance. Accordingly, a relation of PAIgM (and PAIgA) to increased liver destruction of platelets was found in kinetic studies using 111indium-labeled platelets. Taken together, these results suggest a predominant role of PAIgM in the pathogenesis of ITP.