Production and characterization of monoclonal IgM autoantibodies specific for the T-cell receptor

Natural autoantibodies to the T-cell receptor (Tcr) have been identified in all human sera. However, titer, epitope specificity, and isotype vary with physiological conditions, autoimmune diseases, and retroviral infections. The levels of anti-Tcr autoantibodies in rheumatoid arthritis (RA) patients are significantly higher than in normal individuals, and the autoantibodie s are typically IgM. To obtain detailed information on these autoantibodies , we generated B-cell heterohybridomas secreting monoclonal IgM autoantibod ies (mAAbs) from the synovial tissue and peripheral blood of RA patients. W e selected clones secreting mAAbs that bound a major V beta epitope defined by a synthetic peptide that contains the CDR1 region of the V beta 8.1 gen e product. From these we isolated a subset of seven mAAbs that bound a reco mbinant single-chain V alpha/V beta construct containing the peptide epitop e and, also to JURKAT cells which express V beta 8.1. The mAAbs produced by these clones were distinct from each other in their V-region sequences. Ho wever, all the V regions were essentially identical to germline sequences i n both the heavy and light chains. Heavy-chain CDR3 segments ranged in leng th from 17 to 26 residues, did not correspond to any known autoantibodies, and showed extensive N-region diversity in the V(D)J junctions. Five monocl onal autoantibodies use V-H 3 genes, while the remaining two utilized V-H 4 sequences. Light-chain variable regions used were V-kappa 3 (two), V-lambd a 3 (four), and one V-lambda 2. These autoantibodies derived their unique f eatures from their CDR3 segments that could not be aligned with any known s equences.