The B Cell Repertoire in Rheumatoid Arthritis

Abstract

Objective. We sought to compare the frequencies of precursors producing IgM rheumatoid factors (IgM‐RFs) in synovial fluid and peripheral blood B cells from patients with rheumatoid arthritis (RA). Methods. We used limiting‐dilution analysis of Epstein‐Barr virus—activated B cells from seropositive and seronegative patients. B cell precursors producing IgM against insulin, an irrelevant autoantigen, were also assessed for comparison. Results. On average, IgM‐RF—producing precursors were 15‐fold higher in the synovial fluid than in the peripheral blood of seropositive RA patients, but not in seronegative RA patients. The frequency of B cell precursors producing IgM against insulin was lower in the synovial fluid than in the peripheral blood of both the seropositive and the seronegative patient groups; moreover, the concentrations were similar in both groups. Conclusion. The findings provide evidence against a nonspecific accumulation of IgM‐producing cells in the synovial fluid, and suggest that there is an active attraction of the RF‐producing B cell precursors toward sites of inflammation in RA.