9%), to the branched-chain 2-oxo-acid dehydrogenase complex E2 (BCOADC-E2) in 6 of 19 patientsOrgan-specific autoimmune diseases are characterized by (31.6%), and to the 2-oxoglutarate dehydrogenase com-the production of autoantibodies and the destruction of speplex E2 (OGDC-E2) in 1 of 19 patients (5.3%). In a compar-cific tissues. Primary biliary cirrhosis (PBC) has been considative study of sera from the same patients, anti-PDC-ered a model autoimmune disease and a paradigm for dis-E2 antibodies were found in 19 of 19 patients (100%), eases such as Hashimoto's thyroiditis 1 and type I diabetes anti-BCOADC in 9 of 19 patients (47.3%), and anti-mellitus. 2 PBC is characterized by destruction of intrahepatic OGDC-E2 in 4 of 19 patients (21.1%) patients. AMA in bile ducts and production of high-titer autoantibodies against bile were always found together with antibodies of cor-mitochondrial autoantigens. 3 Much work has been directed responding specificities in the serum from the same pa-at the detection and characterization of antimitochondrial tient. Immunoglobulin (Ig)A AMA were found in the bile autoantibodies (AMA). Earlier studies from both our laboraof 9 of 19 patients (47.7%) with PBC; they were specifi-tory and others have shown that AMA react with a series of cally directed against PDC-E2 in 8 of 19 patients (42.1%) highly conserved intramitochondrial proteins, in particular and to BCOADC in 2 of 19 patients (10.5%). Epitope map-the 2-oxo acid dehydrogenase complexes, including the dihyping of IgA anti-PDC-E2 antibodies indicated that, like drolipoylacetyltransferase component of the pyruvate dehyserum autoantibodies, the immunodominant epitope is drogenase complex E2 (PDC-E2), the branched-chain 2-oxo directed against the inner lipoyl domain of PDC-E2. The acid dehydrogenase complex E2 (BCOADC-E2), and the 2-prevalence and antigen reactivity of IgA AMA in sera oxoglutarate dehydrogenase complex E2 (OGDC-E2). [4][5][6][7][8][9][10][11] The correlated completely with IgA AMA in bile. Autoanti-major autoantibody reactivity is directed against the 74-kd bodies against nuclear envelope pore proteins (gp210) protein, PDC-E2. were found in 1 of 8 (12.5%) sera of patients with PBC, Although the pathogenesis of PBC remains unknown, utilibut not in bile. Furthermore, and of particular interest, zation of immunohistochemical techniques, monoclonal, combinatorial derived, and experimentally induced rabbit antibodies specific for PDC-E2 has revealed the selective expression of a cross-reactive molecule at the apex of biliary Abbreviations: PBC, primary biliary cirrhosis; AMA, antimitochondrial autoantibodies; PDC, pyruvate dehydrogenase complex; BCOADC, branched-chain 2-oxo-acid dehydrogeepithelial cells of patients with PBC, but not patients with nase complex; OGDC, 2-oxoglutarate dehydrogenase complex; Ig, immunoglobulin; PBS, primary sclerosing cholangitis or autoimmune hepatitis. 12-14 phosphate-buffered saline; SDS, sodium dodecyl sulfate; BHM, bovine heart mitochondrial Furthermore, deposition of immunoglobul...