Characterisation of Liver membrane autoantibodies determined by indirect immunofluorescence

Indirect immunofluorescence studies were performed using sera and IgG-Fab2 fragments from patients with chronic active hepatitis (CAH) who were positive for a liver membrane antibody (LMA). The specificity was investigated using hepatocytes from humans as well as rabbit, rat, guinea pig and monkey. Only sera also positive for smooth muscle antibody gave staining of lymphocytes and absorption with F-actin from rabbit muscle abolished this as well as all other smooth muscle staining without influencing LMA. It was concluded that LMA, routinely detected by indirect immunofluorescence using rabbit hepatocytes, represents specific binding to non-species-specific membrane antigens which are normal constituents of human hepatocytes. The antigen is separately located, and not cross-reactive with F-actin.