Studies on synthesis of interleukin-6 and gammaglobulin in peripheral blood mononuclear cells of patients with systemic lupus erythematosus.

Peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE) proliferated spontaneously and secreted an elevated level of IgG compared with that of normal controls. However, the levels of interleukin-6 (IL-6) produced by PBMC from patients with SLE with or without pokeweed mitogen (PWM) stimulation showed no significant difference from those of normal controls. The levels of IL-6 secreted spontaneously from PBMC of SLE patients correlated inversely with the percent and the absolute number of CD19 positive cells in PBMC, but not with the levels of IgG and IgM secreted spontaneously from PBMC. There was no significant difference in the levels of IgG produced by PBMC stimulated with IL-6 and also in the levels of IL-6 synthetized by T and B cells between SLE patients and normal controls. These data suggest that IL-6 may not play an important role in the hypergammaglobulinemia in SLE.