The peculiar autoimmunity of primary biliary cirrhosis.
Autoantibodies to mitochondria (AMA, anti-M2) are a serologic hallmark of primary biliary cirrhosis (PBC). These react with three structurally and functionally related multienzymic complexes, the 2-oxoacid dehydrogenase complexes, but chiefly with the E2 subunit of pyruvate dehydrogenase complex (PDC-E2). Their very dose (95%) and specific association with PBC underpins the autoimmune concept of pathogenesis of that disease, notwithstanding several non-congruent features. Detailed studies, including structural analysis of epitopes, do not disclose how these autoantibodies originate. Their ubiquity in PBC has overshadowed the existence of a second set of relatively PBC-specific autoantibodies to nuclear antigens for which reactants have been cloned and characterized. These include centromeric proteins; proteins of the nuclear pore complex; nuclear dot proteins, which include Sp-100 and the promyelocytic leukemia antigen; and a recently identified autoantigen, SOX13. Certain of these reactants are DNA-binding proteins with transcriptional regulatory activity. Thus serum from individuals with the same clinical syndrome can have autoimmune reactivity to disparate mitochondrial and nuclear constituents in different cellular compartments. Antibody probing of phage displayed random peptide libraries, together with epitope scanning using overlapping sequential octameric peptides from the PDC-E2 sequence, showed that the discontinuous motifs MH, FV(E) and SYP contributed to a predicted conformational antibody epitope in the inner lipoyl domain of PDC-E2.
Mackay
I R
IR
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia. ian.mackay@med.monash.edu.au
Whittingham
S
S
Fida
S
S
Myers
M
M
Ikuno
N
N
Gershwin
M E
ME
Rowley
M J
MJ
D000217:Acyltransferases / Q000276:immunology*; D000328:Adult; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D000974:Antibodies, Antinuclear / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D001327:Autoimmune Diseases / Q000276:immunology*; D002467:Cell Nucleus / Q000276:immunology; D002503:Centromere / Q000276:immunology; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D000939:Epitopes / Q000276:immunology; D005260:Female; D006609:High Mobility Group Proteins / Q000276:immunology; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000453:epidemiology / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008930:Mitochondria, Liver / Q000201:enzymology / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000276:immunology; D010455:Peptides / Q000276:immunology*; D015995:Prevalence; D011768:Pyruvate Dehydrogenase Complex / Q000737:chemistry / Q000276:immunology*; D055755:SOXD Transcription Factors; D017678:Sex Distribution
D000888:Antibodies, Anti-Idiotypic; D000974:Antibodies, Antinuclear; D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; C045867:PDHX protein, human; D010455:Peptides; D011768:Pyruvate Dehydrogenase Complex; C491720:SOX13 protein, human; D055755:SOXD Transcription Factors; D000217:Acyltransferases; C033588:dihydrolipoamide acyltransferase; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; C021515:dihydrolipoamide succinyltransferase