In vitro spontaneous anti-DNA antibody production in patients with systemic lupus erythematosus (SLE) was examined. SLE lymphocytes produced IgG and IgM anti-DNA antibody from the third culture day, and reached a plateau on the seventh culture day. This anti-DNA antibody activity in 7-day culture suppernatant was abolished by pretreatment of the lymphocytes with cycloheximide, suggesting de novo immunoglobulin synthesis was required for this spontaneous anti-DNA antibody production. Lymphocytes from patients with rheumatoid arthritis (RA) and other collagen diseases including progressive systemic sclerosis, polymyositis/dermatomyositis, and polyarteritis nodosa did not produce IgG and IgM anti-DNA antibody spontaneously, but SLE lymphocytes produced substantial amounts of IgG and IgM anti-DNA antibody spontaneously. Furthermore, active SLE produced a larger amount of IgG anti-DNA antibody than inactive SLE. We observed a significant negative correlation between the number of Ia+ T cells and IgG, but not IgM, anti-DNA antibody production. Furthermore, spontaneous IgG anti-DNA antibody production was elevated after pretreatment of SLE T cells with anti-Ia and complement, suggesting that Ia+ T cells in SLE bring about suppression of autologous B cells producing IgG anti-DNA antibody.
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