Association of increased immune complexes, platelet IgG and serum IgG in chronic active hepatitis.

Platelet associated IgG (PA-IgG), serum IgG and immune complexes (IC) were measured and correlated with the degree of thrombocytopenia in 32 patients with chronic active hepatitis (CAH), classified as of autoimmune type in 24 and cryptogenic in eight. Of the 32 patients, 24 had raised PA-IgG and 18 of these were thrombocytopenic (greater than 150 X 10(9) platelets/1); in only two thrombocytopenic patients was the level of PA-IgG not increased. Platelet counts showed a significant inverse logarithmic correlation with PA-IgG levels (r = 0.456, P less than 0.01). Twelve patients had raised levels in serum of ICs, 11 of these also had raised PA-IgG and 10 of these 11 were thrombocytopenic. Serum IgG was raised in 10 patients and correlated with PA-IgG (r = 0.489, P less than 0.01). Of the 24 patients with autoimmune CAH, 13 had low platelet counts and 10 had raised levels of PA-IgG whereas of the eight patients with cryptogenic CAH, seven had raised PA-IgG and all were thrombocytopenic. These results for patients with CAH show that raised levels of circulating ICs are associated both with thrombocytopenia and with raised PA-IgG, and support the hypothesis that serum IgG and/or ICs may influence amounts of PA-IgG.