Studies on circulating soluble immune complexes of the liver disease. 6. Comparative studies of 125I-pRF inhibition assay, 125I-Clq inhibition assay and 125I-Clq binding assay.

Inhibition assay of 125I-C1q binding to IgG-p-azobenzamidoethyl Sepharose 6B (IgG-Sepharose) by immune complexes was developed for the detection of circulating soluble immune complexes in the liver disease and was compared with polyclonal rheumatoid factor (pRF) binding inhibition assay and with C1q binding assay. The C1q inhibition assay was proved to be very sensitive, reproducible and rapid. Sucrose density gradient ultracentrifugal analysis showed that the assay could detect aggregates of human IgG (AHGG) larger than 19s. C1q inhibition activity (C1qIA) correlated with severity of the liver disease, defined by histological criteria. The highest C1qIA was observed in sera of patients with primary biliary cirrhosis, followed by liver cirrhosis, fulminant hepatitis, chronic aggressive hepatitis (2B), lupoid hepatitis and hepatocellular carcinoma in the order. There were correlations of C1qIA with serum gamma-globulin levels, sero-positivity for rheumatoid factor and hepatitis B surface antigen, and significant correlations existed also among pRFIA, C1qIA and C1qBA. Ultracentrifugal analysis of sera from patients with the liver disease showed that ClqIA demonstrated two sizes of immune complexes, 7s and larger than 19s, while complexes larger than 8s were seen in pRFIA.