Isolation of human anti-branched chain alpha-oxo acid dehydrogenase-E2 recombinant antibodies by Ig repertoire cloning in idiopathic dilated cardiomyopathy

The generation of human monoclonal autoantibodies is critical for understan ding humoral immune response in autoimmunity. in this study, Ig gene repert oire cloning was performed from a regional lymph node of a patient with idi opathic dilated cardiomyopathy (IDCM), and the resulting combinatorial IgG library was screened with bovine-branched chain;cr-oxo acid dehydrogenase-E -2 (BCOADC-E2), one of the autoantigens in IDCM, After three rounds of affi nity selection, we isolated three human recombinant IgG Fab molecules, name d BC1, BC2 and BC3, that specifically react with BCOADC-E2 by ELISA, intere stingly, BC2 showed weak cross-reactivity to,pyruvate dehydrogenase complex -E2 (PDC-E2), another mitochondrial antoantigen found-in primary biliary ci rrhosis (PBC), and their kappa light chain genes have 95% homology with :a light chain of the human anti-DNA antibody. Although the exact pathogenic e ffect of anti-BCOADC-E2 autoantibodies is still unknown:in IDCM, the potent ial binding specificity and,limited light chain gene usage,of our recombina nt IgG molecules may shed light on the initial mechanism as to how autoanti bodies start developing in IDCM.