Liver membrane antibodies (LMA) recognize a 26-kD protein onthe hepatocellular surface

Abstract

SUMMARY: Sera from 82 patients with chronic inflammatory liver diseases and from patients with systemic lupuserythemalosus (SLE). rheumatoid arthritis (RA) and Hashimoto's thyroiditis were studied byimmunoblotting against purified liver plasma membranes (LPM) and soluble liver protein (SLP)fractions from different species after previous separation by SDS-PAGE. Eighteen of 19 sera withLMA of IgG type in immunofluorescencc assay and six LMA-negatiuve sera (three sera from patientswith RA) showed antibodies of the IgG or IgM classes against a protein with a molecular weight of 26kD which was present in LPM and SLP fractions from rats, rabbits, pigs and humans. The reactionwith 26-kD liver protein did not correlate with other known autoantibody-antigen systems. All serawere negative in the 26-kD region with liver mitochondria, liver microsomes and soluble proteins ofkidney (with one exception), heart and gut from the rat. The 26-kD protein was purified by affinitychromatography on immobilized anti-26-kD protein antibodies from patients, eluted from the 26-kDband of immunoblots. Studies with purified 26-kD liver protein and with SLP as antigens afterseparation in two-dimensional electrophoresis confirmed that patient serum and experimental rabbitantiserum react with the same protein. Eluted patient antibodies and rabbit antisera showed a linearfluorescence pattern on isolated hepatocytes from rat and rabbit. The data indicate that one of thetarget antigens of LMA is a species-nonspecific 26-kD protein located on the hepalocellular surface.