Liver membrane autoantibodies: methods for their detection and clinical significance

There is a growing evidence suggesting that immunological reactions against liver membrane antigens are involved in the process of ongoing hepatic injury in chronic active liver diseases (CALD). Liver specific lipoprotein (LSP) has been described as one of the target antigens of the liver cell membrane. Autoantibodies against LSP (anti-LSP) are predominantly directed against organ-specific determinants of a low density LSP subfraction (1.08-1.10 g/ccm). Anti-LSP detected in acute viral hepatitis are mainly directed against species-specific, whereas those in chronic active hepatitis are mainly directed against non-species-specific, determinants of the LSP complex. Further liver membrane autoantibodies were found to react with additional antigens of the hepatocellular membrane (LM-Ag). These liver membrane autoantibodies (LMA) are disease-specific for autoimmune type CALD. The detection of liver membrane autoantibodies by indirect immunofluorescence on isolated rabbit hepatocytes (LMA-test) is clinically important since this subgroup of CALD does well respond to immunosuppressive therapy. It is still unknown, however, whether these liver membrane autoantibodies are really involved in the immunopathogenesis of CALD via antibody dependent cellular cytotoxicity (ADCC) or whether they are a phenomenon secondary to liver cell destruction. Nevertheless they represent diagnostic markers by which one can classify subgroups of CALD with different etiologies. A further characterization of liver membrane antibody-antigen systems could lead to a more precise evaluation of the clinical relevance of liver membrane autoantibodies.