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 rheumato id factors (RF), we established stable hybridomas and Epstein-Barr vir us-transformed B cell lines from the synovial fluid or peripheral bloo d of three patients with rheumatoid arthritis and one patient with sys temic lupus erythematosus. 17 cell lines were obtained that produced h igh-titer immunoglobulin M (IgM) RF that reacted exclusively with rabb it but not human IgG or IgG of other mammalian species. Certain anti-r abbit IgG RF also had specificity for other mammalian antigens (Ag), i ncluding cytoskeletal proteins and intracellular proteins found in HeL a cells, as well as for Ag present in an extract prepared from the cel l 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), incl uding 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 a cid sequences of the lambda chains of these IgM lambda RF confirmed th eir serological classification as lambdaIII, and they were further cla ssified as members of the relatively uncommon VlambdaIII subgroup, des ignated V(lambda)IIIb. Based on cDNA analyses, nine were the product o f three different V(lambda)IIIb germline genes. Two such genes, design ated hsiggll150 and hsiggll295, were cloned and sequenced from genomic DNA. Unique combinations of these V-H and V(lambda)IIIb genes could b e related to distinctive patterns of reactivity among the IgM lambda R F. Although the V-H and V-lambda regions of these Abs were expressed p rimarily 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 oth er protein, cellular, and bacterial Ag, provides new insight into the pathogenesis of RA and related diseases.