Detection and characterization of liver membrane autoantibodies in chronic active hepatitis by a solid-phase radioimmunoassay.

A solid-phase radioimmunoassay was developed to detect antibodies to liver membrane antigens in sera of patients with HBsAg-negative and -positive liver diseases and primary non-hepatic autoimmune diseases. Ten of fourteen patients with HBsAg-negative CAH had autoantibodies detected by RIA; negative results were obtained with sera of seven patients with HBsAg-positive acute and chronic liver diseases, six patients with miscellaneous liver diseases, including two patients with PBC, two healthy blood donors and seven patients with primary non-hepatic autoimmune diseases. Antibodies detected by RIA correlated with liver membrane autoantibodies (LMA) found by indirect immunofluorescence; no correlation was observed with AMA, ANA and SMA. Species-cross-reacting antibodies could be absorbed by preincubation with isolated plasma cell membranes prepared from rabbit livers. Liver membrane autoantibodies detected by RIA were directed against three different antigen fractions obtained from Sepharose 6B chromatography including LSP and LM-Ag. Only three of ten antibodies were directed against species-specific determinants; others cross-reacted with rabbit antigens. Only the antibody to LSP was organ-specific, all others cross-reacted with kidney proteins. Ferritin, human serum albumin and human plasma lipoprotein were excluded as target antigens. Although several sera reacted with identical molecules a remarkable heterogeneity of liver membrane autoantibodies was observed.