INCREASED RESPONSIVENESS OF RHEUMATOID FACTOR-PRODUCING B-CELLS IN SERONEGATIVE AND SEROPOSITIIVE RHEUMATOID-ARTHRITIS

Objective. To compare the frequencies and responsiveness of rheumatoid factor (RF)-producing B cells in the peripheral blood of patients wit h seronegative and seropositive rheumatoid arthritis (RA). Methods. Fr equencies of IgM+, IgG+, and RF+ B cells were determined by limiting-d ilution analysis of purified peripheral blood B cells from 6 patients with seropositive RA, 8 patients with seronegative RA, and 7 normal co ntrols. B cell help was provided by cloned T helper cells, which were stimulated by either anti-CD3 or the bacterial superantigen staphyloco ccal enterotoxin D (SED). IgM and IgG antibodies and RF in culture sup ernatants were detected by enzyme-linked immunosorbent assay. Results. In the presence of anti-CD3-stimulated T helper cells, 2-10% of B cel ls from normal individuals secreted IgM and IgG antibodies. The freque ncy of RF+ B cells was low and ranged from 1:182 to 1:885 (RF+: IgM+) B cells. In patients with seropositive RA, the numbers of Ig-producing B cells were reduced by a factor of 2, while the fraction of RF+ B ce ll precursors was expanded by more than 50-fold (7-20% of IgM+ B cells ; P = 0.004). Patients with seronegative RA had higher frequencies of RF-producing B cells (1.5-6% of IgM+ B cells) than normal individuals (P = 0.002), but not to the same extent as seropositive patients (P = 0.002). Stimulation of B cells using SED preferentially induced RF+ B cells in normal controls and in patients with seronegative and seropos itive RA. Conclusion. B cell precursors with the potential to secrete RF were detectable in high frequencies in normal individuals and in pa tients with seropositive and seronegative RA. In all donors, these B c ells could be stimulated with the bacterial superantigen SED. In norma l individuals, RF+ B cells remained nonresponsive to help provided by anti-CD3-activated T cells, but were responsive in RA patients. Serone gative and seropositive RA form a continuous spectrum of disease, with a higher number of RF-secreting B cells in the seropositive patients.