Abstract
Background/Aims : The major antigens for anti-mitochondrial autoantibodies in primary biliary cirrhosis (PBC) are the lipoyl-containing components of 2-oxo acid dehydrogenase complexes. Autoantibodies against the E1 α subunit of the pyruvate dehydrogenase complex (PDH) also have been found, but those against the E1 α subunit of branched-chain 2-oxo acid dehydrogenase complex (BCKADH) have not been detected. We investigated the occurrence of BCKADH-E1 α-specific autoantibodies by employing the purified human antigen. Methods : The reactivities of PBC sera against purified antigens were assessed by ELISA and by immunoblotting analysis. The specificity of immunoreactivity was confirmed by absorption tests and affinity-purified antibodies. Results : Fourteen out of 27 PBC sera reacted with BCKADH-E1 α, and these same sera also reacted with BCKADH-E2. No PBC sera reacted with BCKADH-E1 β. The reactivity of PBC sera with BCKADH-E1 α was removed only when the sera were pre-absorbed with this antigen. However, reactivities to BCKADH-E2 and PDH-E1 α were retained. Affinity-purified antibodies to BCKADH-E1 α reacted with BCKADH-E1 α, but not PDH-E1 α. Thus, it was confirmed that anti-BCKADH-E1 α did not cross-react with either BCKADH-E2 or PDH-E1 α. Conclusions : BCKADH-E1 α-specific autoantibodies were found in the sera of PBC patients. The antibodies seem to occur subsequent to the anti-BCKADH-E2 antibody production, supporting the concept of intermolecular determinant spreading.
Published Version
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