Autoantibody against a 78 kDa membrane protein of HepG2 cell in the sera of patients with alcoholic liver diseases.

Sera from 14 normal control subjects, 30 patients with alcoholic liver diseases (fatty liver, n = 8; hepatitis, n = 13; liver cirrhosis, n = 9), 7 controls with chronic hepatitis B, and 8 controls with chronic hepatitis C were masured for their concentrations of antibodies against HepG2 membrane protein by a binding assay utilizing 125I-labeled protein A. When the cut-off level was set as the mean value plus 2 SD of normal control subjects, the incidence of positivity was 75%, 69.2%, and 77.8% in patients with alcoholic fatty liver, alcoholic hepatitis, and alcoholic cirrhosis, respectively. Both the mean serum antibody values and the positive incidence were significantly higher in patients with alcoholic liver diseases than in either the normal controls or in the control patients with chronic hepatitis. Sodium dodecylsulfate polyacrylamide gel electrophoresis of 125I-labeled HepG2 membrane protein precipitated with IgG from patients with alcoholic liver diseases revealed an immunoreactive band at a molecular weight of 78,000 daltons (gp78). The antibody activity remained after immunoabsorption by human liver-specific lipoprotein (LSP) but decreased when HepG2 cells were pre-treated with trypsin or neuraminidase. Consequently, gp78 appears to be a glycoprotein distinct from LSP, and is specifically recognized by IgG from patients with alcoholic liver diseases. This assay may provide a new system to measure autoantibody to hepatocytes in alcoholic liver diseases.