Enhancement of in vitro immunoglobulin synthesis of rheumatoid lymphocytes by aggregated human gamma globulin.

In vitro immunoglobullin synthesis by lymphocytes of patients with rheumatoid arthritis (RA) was enhanced by the addition of heat-aggregated human IgG. Stimulation occurred in the presence of fresh seropositive autologous plasma and was abolished by heat inactivation. By contrast, no significant stimulation was induced in lymphocytes from patients with miscellaneous arthritides and normal subjects cultured in the presence of either fresh autologous plasma or fresh normal AB serum. Although stimulation of RA lymphocytes did not occur in the presence of fresh AB serum, it did when purified IgM rheumatoid factor was added to this serum. These results suggest that immune complexes formed between aggregated IgG and rheumatoid factor in the presence of complement stimulate immunoglobulin synthesis in the peripheral blood lymphocytes of patients with RA.