Circulating immune complexes and platelet IgG in various diseases.

Correlation between platelet associated IgG (PAIgG), platelet count, and plasma polyethylene glycol (PEG) precipitable IgG immune complex (IC) like material was tested in normal subjects and patients with immune thrombocytopenia (ITP), systemic lupus erythematosus (SLE) and various types of liver disease. Elevated IC were observed in 27% and 22% of ITP and recovered ITP, respectively. A significant inverse correlation between platelet count and PAIgG was demonstrable in the ITP group. A significant direct correlation between platelet count and IC was found only in SLE patients. Impaired reticuloendothelial cell (RE) Fc receptor function in SLE patients is suggested as a possible explanation for the data. If receptor function was normal in SLE patients, lower IC levels and lower platelet counts would have been expected.