Hepatocyte plasma membrane antigens. I. Determination of antibodies bound to the hepatocyte plasma membrane by 125I-protein A binding assay.

Anti-liver-specific membrane lipoprotein (anti-LP-1) and anti-Tamm-Horsfall glycoprotein (anti-THGP) rabbit antibodies were found to bind to Chang liver cells, a cultured human hepatocyte cell line, and PLC/PRF/5, a hepatoma cell line. The antibodies bound were determined by an immunofluorescence staining and a semiquantitative 125I-protein A binding assay. The 125I-protein A binding assay was successfully adapted to determine anti-hepatocyte plasma membrane antibodies in sera of patients with lupoid hepatitis and chronic active hepatitis. The percentage of 125I-protein A bound in 10 normal subjects were 1.5 +/- 0.4 (mean +/- standard deviation) for PLC/PRF/5 and 1.6 +/- 0.6 for Chang liver cell, while those in 2 patients with lupoid hepatitis were 7.2 +/- 0.3, 5.9 +/- 0.1, and those in 8 patients with chronic active hepatitis 3.9 +/- 1.3, 3.2 +/- 1.5, respectively. Furthermore, a blocking study revealed that LP-1 and THGP were partially involved in antigen sites recognized with anti-hepatocyte plasma membrane antibodies in sera of a patient with lupoid hepatitis. The retaining ability of antibody binding to the hepatocytes after the absorption with non-hepatocyte cells suggested the presence of antibodies specific for the hepatocyte plasma membrane in the patient's serum.