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In vitro stimulation of peripheral blood lymphocytes from two rheumatoid arthritis patients with pokeweed mitogen (PWM) and Epstein-Barr virus (EBV) induced differing sets of IgM rheumatoid factor (IgM-RF) idiotypes. Thus, in either patient. 71–82% of the IgM-RF induced by PWM, but only 30% of the IgM-RF induced by EBV, shared individually specific idiotypes with serum IgM-RF. These results suggest that differing populations of autoreactive B lymphocytes were induced by the two mitogens. PWM, a T-cell-dependent mitogen, induced the same RF-bearing B cells that were active in vivo . In contrast, EBV, a T-cell-independent mitogen, stimulated predominantly an inactive population of RF precursor B lymphocytes.

The immunoglobulin light chain heterogeneity of two autoantibodies, IgM anti-IgG and IgM anti-human thyroglobulin, induced by Epstein-Barr virus (EBV) stimulation of peripheral blood lymphocytes from young (20–40 years old) and aged normal adults (≥75 years old), as well as patients with rheumatoid arthritis and thyroid disease, has been analyzed. The IgM anti-IgG autoantibodies from the aged were markedly enriched in κ light chain-bearing molecules, when compared to the total IgM in the same cultures, in a pattern similar to the IgM anti-IgG from rheumatoid arthritis patient lymphocyte cultures. On the contrary, the IgM anti-IgG from young adult lymphocytes cultures, and the IgM anti-thyroglobulin from all groups, had κ to λ light chain ratios indistinguishable from the total IgM. These results suggest that advancing age in normal people is accompanied by a selective restriction in the heterogeneity of the EBV inducible anti-IgG antibodies. The pattern resembles that seen in patients with rheumatoid arthritis.