Molecular analysis of rheumatoid factors derived from rheumatoid synovium suggests an antigen-driven response in inflamed joints

Objective. Understanding the molecular genetic basis for rheumatoid factor (RF) production is necessary to a better understanding of the etiology and pathogenesis of rheumatoid arthritis (RA). We sought to define the genetic basis of RF in RA. Methods. The heavy and light chain variable region genes encoding 4 human monoclonal RF were cloned and sequenced using the polymerase chain reaction and the dideoxynucleotide chain-termination method. Results. The heavy and light chains of the C6 RF and the light chain of the G9 RF were encoded by 3 new RF-related Ig V-region genes. The heavy and light chains of D5 and G4 RFs were identical; most of their mutations caused amino acid substitutions. Conclusions. The RF-related Ig V-region gene repertoire is large and is still expanding. The data from D5 and G4 strongly suggest that these 2 RFs arise in an antigen-driven response in rheumatoid synovium. The presumed germline V genes for C6 may represent disease-specific RF-related V genes.