In vitro regulation of B cell differentiation by interleukin-6 and soluble CD23 in systemic lupus erythematosus B cell subpopulations and antigen-induced normal B cells.

Polyreactive systemic lupus erythematosus (SLE) B cells were compared with antigen-induced SLE and normal B cells for their interleukin-6 (IL-6) and soluble CD23 requirements. Unlike normal B cells, secretion of antibody by SLE B cells in serum-free medium was not enhanced by exogenous IL-6. Anti-IL-6 antibodies inhibited immunoglobulin production in cultures of normal and SLE B cells, which suggests that IL-6 is required for B cell differentiation. SLE culture supernatants had elevated levels of IL-6, which explains the poor response of the SLE cells to exogenous IL-6. Soluble CD23 enhanced the responses of cells from normal subjects and SLE patients.