HUMAN RHEUMATOID FACTORS WITH RESTRICTIVE SPECIFICITY FOR RABBIT IMMUNOGLOBULIN-G - AUTO-REACTIVITY AND MULTI-REACTIVITY, DIVERSE V-H GENE SEGMENT USAGE AND PREFERENTIAL USAGE OF V(LAMBDA)IIIB

To determine the molecular and functional properties of human rheumatoid factors (RF), we established stable hybridomas and Epstein-Barr virus-transformed B cell lines from the synovial fluid or peripheral blood of three patients with rheumatoid arthritis and one patient with systemic lupus erythematosus. 17 cell lines were obtained that produced high-titer immunoglobulin M (IgM) RF that reacted exclusively with rabbit but not human IgG or IgG of other mammalian species. Certain anti-rabbit IgG RF also had specificity for other mammalian antigens (Ag), including cytoskeletal proteins and intracellular proteins found in HeLa cells, as well as for Ag present in an extract prepared from the cell wall of group A streptococci. 13 of the 17 RF contained lambda-type light (L) chains, of which 12 were classified serologically as members of the lambda-L chain variable region (V-lambda) subgroup, designated VlambdaIII. The heavy chain V region (V-H) and V-lambda sequences of nine of these IgM lambda RF were determined at the cDNA level. Five V-H genes in three V-H families were used by these antibodies (Ab), including V(H)1 (dp21/1-4b and dp10 [51p1]/ hv1051), V(H)3 (dp38/3-15 and dp77/13-21), and V(H)4 (dp70/4-4b). The deduced V gene-encoded amino acid sequences of the lambda chains of these IgM lambda RF confirmed their serological classification as lambdaIII, and they were further classified as members of the relatively uncommon VlambdaIII subgroup, designated V(lambda)IIIb. Based on cDNA analyses, nine were the product of three different V(lambda)IIIb germline genes. Two such genes, designated hsiggll150 and hsiggll295, were cloned and sequenced from genomic DNA. Unique combinations of these V-H and V(lambda)IIIb genes could be related to distinctive patterns of reactivity among the IgM lambda RF. Although the V-H and V-lambda regions of these Abs were expressed primarily as germline-encoded sequences, four of nine multireactive Abs had extensive V region mutation, indicative of an Ag-driven process. The finding that (lambda)IIIb L chains are preferentially found among anti-rabbit IgG RF, and that some of these Ab have specificity for other protein, cellular, and bacterial Ag, provides new insight into the pathogenesis of RA and related diseases.