The B cell repertoire in rheumatoid arthritis. II. Analysis of rheumatoid factors bearing the IdRQ cross-reactive idiotype.

With the view of studying whether rheumatoid factors (RFs) produced in rheumatoid arthritis (RA) were different from those synthesized in physiological situations, we analyzed the usage of a cross-reactive idiotype (IdRQ) previously reported to be specific for RA RFs. Using EBV immortalization of circulating B cells, we prepared monoclonal RFs from patients with RA and matched controls. In both groups between 1/2 and 2/3 of the monoclonal RFs bore IdRQ. Using limiting dilution analysis, we studied the frequencies of the EBV-activated B cells able to synthesize immunoglobulins bearing IdRQ. In patients and in controls, on average, 1/3 of the RF-secreting cells used IdRQ and around 2/3 of the synthesized IgM bearing IdRQ were devoid of RF activity. These results show that precursor cells containing the germline gene encoding IdRQ are present in similar quantities in RA patients and healthy individuals, and that the IdRQ cross-reactive idiotype, although interesting for the study of the B cell repertoire, is probably not useful as a marker for susceptibility to RA.