Antimitochondrial antibodies (AMA) are the serologic hallmark of primary biliary cirrhosis (PBC). However, depending on the clinical laboratory, from 5% to 17% of PBC patients are consistently AMA-negative, using native mitochondrial antigens and a variety of conventional assays including immunofluorescence (IMF) and enzyme-linked immunosorbent assay (ELISA). The major immunoreactive mitochondrial autoantigens are the E2 members of the 2-oxo-acid dehydrogenase complex family, including pyruvate dehydrogenase complex-E2 (PDC-E2), branched chain 2-oxo acid dehydrogenase complex-E2 (BCOADC-E2), and oxo-glutarate dehydrogenase complex-E2 (OGDC-E2); cDNAs of these proteins have now been cloned, sequenced, and their B-cell epitopes defined. In the present study, we cloned cDNAs encoding these proteins from human, not bovine, sources, and expressed the recombinant proteins in a newly developed ELISA that employs a unique Escherichia coli buffer, and compared the data with previous assays using both AMA-positive and -negative patients. Using this new assay and our criteria for positive as an optical density (OD) greater than 10 SD above the mean of control sera, the AMA-positive rate of 191 PBC sera was 94% (
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