Occurrence and significance of IgG liver membrane autoantibodies (LMA) in chronic liver diseases of different aetiology.

The prevalence of liver cell membrane antibodies (LMA) was evaluated in the sera of 124 untreated patients with various chronic liver diseases, in 17 acute hepatitis patients and in 40 normal controls by indirect immunofluorescence on rabbit hepatocytes, isolated by non-enzymatic method. The presence of LMA was compared with the presence of HBs Ag, anti-HBc and non-organ specific autoantibodies (anti-nuclear antibody, ANA; smooth muscle antibody, SMA; anti-mitochondrial antibody, AMA; liver-kidney microsomal antibody, LKM). LMA was found in 83% of autoimmune chronic active liver disease (CALD), in 47% of cryptogenic CALD and in 42% of primary biliary cirrhosis (PBC). LMA prevalence both in HBsAg positive and HBsAg negative/anti-HBc positive CALD was 11%, significantly lower than in the other three groups. In the cryptogenic group the prevalence of non-organ specific autoantibodies was significantly lower than LMA prevalence. The 35 LMA positive sera were titred to end point dilution. Autoimmune cases presented titres higher than those of all the other groups. Adsorption experiments showed that in autoimmune cases LMA fluorescence is not blocked by pre-incubation with liver antigens LSP and LP2, while a mild blocking effect was observed in some HBsAg positive cases or PBC sera. No cross-reaction with mitochondrial antigens was observed in PBC sera. LMA can still be considered a marker of autoimmune CALD only when present at high titre and without cross-reactivity with other liver antigens.