title: Sera from patients with tuberculosis recognize the M2a-epitope (E2-subunit of pyruvate dehydrogenase) specific for primary biliary cirrhosis.
abstract: Anti-M2 antibodies in primary biliary cirrhosis (PBC) have been shown to react with the alpha-ketoacid dehydrogenase complex of the inner mitochondrial membrane consisting of six epitopes (E2 subunit of the pyruvate dehydrogenase complex (PDC), 70 kD; protein X of the PDC, 56 kD; alpha-ketoglutarate dehydrogenase complex, 52 kD; branched-chain alpha-ketoacid dehydrogenase, 52 kD; E1 alpha subunit of PDC, 45 kD; and E1 beta-subunit of PDC, 36 kD). These epitopes are also present in the M2 fraction which is a chloroform extract from beef heart mitochondria. The E2 subunit of the PDC at 70 kD (M2a), especially, is a major target epitope which is recognized by about 85% of all PBC sera. However, analysing sera from 28 patients with active pulmonary tuberculosis it became evident that 12 (43%) also recognized the PDC-E2 subunit (M2a), as shown by Western blotting using the M2 fraction, the purified PDC, and the recombinant PDC-E2. In contrast, only two of 82 patients with other bacterial and viral infections including 25 patients with Escherichia coli infections reacted with the PBC-specific epitope at 70 kD. Naturally occurring mitochondrial antibodies (NOMA) were present in 54% of the patients with tuberculosis and in 50% of patients with other infectious disorders. They recognized either a determinant at 65 kD (epsilon) or at 60/55 kD (zeta/eta). None of the sera from 100 blood donors had anti-M2 but 14 had NOMA. Testing anti-M2 and NOMA-positive marker sera by Western blotting against membrane fractions derived from mycobacteria and E. coli it could be shown that--like mammalian mitochondria--they contain both the PBC-specific M2 antigen as well as the non-PBC-specific naturally occurring mitochondrial antigen system (NOMAg). The observation that PBC-specific antibodies were preferentially induced in patients suffering from a mycobacterial infection may provide some new clues to the still unknown etiology of PBC.
authors.affiliation: Medizinische Klinik, University of Tübingen, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Klein
authors.forename: M
authors.initials: M
authors.lastname: Wiebel
authors.forename: S
authors.initials: S
authors.lastname: Engelhart
authors.forename: P A
authors.initials: PA
authors.lastname: Berg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D001424:Bacterial Infections / Q000276:immunology; D015153:Blotting, Western; D000939:Epitopes; D004926:Escherichia coli / Q000276:immunology; D005260:Female; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000276:immunology*; D008297:Male; D008566:Membranes / Q000276:immunology; D008875:Middle Aged; D008928:Mitochondria / Q000276:immunology; D011768:Pyruvate Dehydrogenase Complex / Q000276:immunology*; D014376:Tuberculosis / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D011768:Pyruvate Dehydrogenase Complex