Monoclonal IgM, IgG, and IgA human rheumatoid factors produced by synovial tissue-derived, EBV-transformed B cell...

In an effort to study disease-related autoantibodies in rheumatoid arthritis (RA), rheumatoid factor (RF)-producing B cell lines were developed from the heterogeneous B cell populations infiltrating the synovial tissue of patients with arthritis. Over 125 EBV-transformed B cell cultures were derived from three patients: one with early pre-erosive RA, one with advanced RA, and one with osteoarthritis (OA). IgM, IgG, and IgA RF-producing B cell lines were found in all three series but with several significant differences. In each of the two RA patients, 22% of the Ig-producing cell lines secreted RF compared to 7% in the OA patient. The isotypes of these RF were mostly IgM in the early RA (62%) and the OA patient (60%) as contrasted to predominantly IgA (75%) and, to a lesser extent, IgG (12.5%) in the advanced RA patient. Analyses of the light (L) chain composition of these RF revealed that 82% of the IgM RF used kappa L chains whereas only 31% of the non-IgM RF used kappa chains. Antigen-binding analyses of these RF revealed that all the synovial tissue-derived RF from the advanced RA patient exhibited antigen binding specificities restricted to a narrow range of gamma globulins. In contrast, the synovial RF of the other two patients were either reactive with a broader spectrum of gamma globulins or reactive with a variety of unrelated antigens. In every instance, the gamma globulin-specific RF were of all three major isotypes whereas the polyreactive RF were restricted to the IgM isotype. These data demonstrate that synovial B cells from both RA and OA patients can produce RF and that significant differences can exist among patients in the percentage of RF generated and their H and L chain isotype distribution. The reversal of the kappa:lambda ratio among the IgG and IgA RF and the more restricted antigen-binding specificities of the IgG and IgA vs IgM RF suggest that a non-stochastic, possibly antigen-driven selection process was involved in their generation. The relevance of these differences in RF precursor frequency, H and L chain distribution, and antigen specificity to these two diseases warrants further investigation.