Mitochondrial antibodies in chronic liver diseases and connective tissue disorders: further characterization of the autoantigens.
The heterogeneity of mitochrondrial autoantibodies in a variety of diseases states has been critically re-examined by a combination of immunofluorescence staining (IFL) and complement fixation tests (CFT). The different mitochondrial IFL patterns described by other workers were confirmed and extra criteria using new substrates are presented for their differential recognition. Biochemically defined mitochondrial subfractions were used in the CFT to confirm and extend the IFL classifications. The 'M1' cardiolipin antibodies of syphilis did not react with the ATPase fraction but the antigen was present in all membrane preparations and found to be chemically resistant. The major antibody specificity of the 'M3' pattern associated with drug-induced pseudolupus syndrome is a firmly bound, outer membrane component; and a second, minor reactivity is apparently to a mercurial-insensitive antigen present in the chloroform-released ATPase preparation. The 'M5' antibody pattern correlates with a digitonin-sensitive outer membrane component. Although it was not possible to differentiate within the group of liver diseases between the 'M2' antibodies of primary biliary cirrhosis and the previously described 'M4' antibodies of other chronic liver diseases, several antibody specificities were demonstrated. All sera from liver disease patients contain the antibody directed against a mercurial-sensitive protein found in the chloroform-released ATPase preparation, and, in addition, varying titres of antibodies against two or more mercurial-resistant membrane components, of which at least one is on the inner membrane and one on the outer membrane.