Antibodies to liver cell membrane antigens in chronic active hepatitis (CAH). III. Partial characterization of the liver cell membrane antigens and comparison of reactivities in sera from patients with various liver diseases.

The reactivity of sera in liver diseases was investigated by an immunoradiometric assay for antibody to liver membrane antigens (LMAg). Serum reactivity was similar using glutaraldehyde treated hepatocytes from man and several animals, but the reactivity with human hepatocellular carcinoma cell lines was weak and irregular. F(ab)2 fragments from reactive sera were used in competitive inhibition experiments to ascertain whether anti-LMAg from different liver diseases reacted with the same or different antigenic determinants of the liver membrane. Sera from different patients with autoimmune CAH reacted predominantly with the same membrane components, as did sera from hepatitis B virus associated CAH (CAH-B); however sera from acute viral hepatitis A did not and, since such sera were reactive to LMAg in the assay, other membrane antigens are presumably involved. Enzymatic treatment of viable hepatocytes was performed to determine the nature of the reactive antigen(s): proteases or periodate resulted in reduced binding of reactive sera, but neuraminidase did not, suggesting that the LMAg recognized by CAH sera comprises species non-specific membrane glycoproteins. We conclude, on the basis of quantitative data from a immunoradiometric assay, that antibody to LMAg is more probably reactive than pathogenic, and that assessment of the antigenicity of specific membrane components is necessary.