Autoantibodies to liver antigens in chronic liver disease. I. A radioimmunoassay for antibody to liver membrane antigens.

A radioimmunoassay using a single cell suspension of glutaraldehyde-treated monkey hepatocytes was developed to measure antibody in human serum to liver membrane antigens. Hepatocytes were exposed to doubling dilutions of test sera in microtitre trays and binding of serum IgG was determined by exposure of the washed cells to 125I-labelled staphylococcal protein A. Specificity of binding was established according to several criteria including use of non-hepatic cells such as monkey kidney cells and various cell lines, IgG depletion of serum, absorption of binding activity by pre-exposure of serum to liver cells, and demonstration that binding was mediated by the F(ab) rather than Fc portions of immunoglobulin molecules. This radioimmunoassay distinguished autoimmune-type chronic active hepatitis (CAH) from other categories of liver disease. It should prove useful for diagnosis and classification of cases of CAH, and could facilitate identification of a liver-specific membrane antigen relevant to pathogenesis of autoimmune hepatitis.