Characteristics of C3b-binding in chronic liver diseases

We examined sera from 71 patients, 27 with alcoholic liver disease (ALD), 27 with chronic active hepatitis (CAH), and 17 with primary biliary cirrhosis (PBC), by enzyme-linked immunosorbent assay for the presence of C3b-binding IgG, IgM, and IgA activity (immune complexes and immunoconglutinins). Elevated C3b-binding IgG activity was found in the sera of patients with CAH, PBC (p less than 0.001), and ALD (P less than 0.01). C3b-binding IgM activity was elevated only in CAH and PBC (p less than 0.001) and normal in ALD. Significantly elevated C3b-binding IgA activity was found in all three types of liver disease (p less than 0.005), but it was more prominent in ALD and, moreover, correlated with the severity of the alcoholic liver injury. Ultracentrifugation studies showed that CAH and PBC C3b-binding IgG activity was located in the intermediate (7S-19S) fractions, C3b-binding IgM activity in the heavy (less than 19S) fractions, and C3b-binding IgA activity in the intermediate and partly in the heavy fractions of the sucrose gradient. In ALD, a slight C3b-binding IgG and IgA activity was found in the intermediate fractions of the gradients, but it was most abundant in the heavy fractions. If C3b-binding material is pathogenic, the results suggest that immunopathogenic mechanisms of CAH and PBC differ from those of alcoholic liver injury.