ABSTRACT
Interleukin (IL)-10 accelerates the IgE production of anti-CD40- and IL-4-stimulated PBMC by enhancing the IL-6 production of T lymphocytes or antigen-primed spleen cells, in addition to its role as a regulator of the inflammatory responses. To further investigate the mechanisms enhancing IgE synthesis, we determined the effect of somatropin as well as IL-10 on the secretion of Dermatophagoides farinae (Df)-specific IgE by K7 cells, which originate from an EBV-immortalized cell line. Df-pulsed autologous T cells, as well as the supernatants of these cultures, increased the synthesis of Df-specific IgE. Antigen-specific IgE was also enhanced when K7 cells were treated with anti-CD40 antibody and with both IL-4 and IL-10, or with IL-4 and IL-10 without anti-CD40 antibody. The treatment of K7 cells with anti-CD40 antibody and IL-4, or anti-CD40 antibody and IL-10 did not increase IgE production. The Df-specific IgE activity of the supernatants of K7 cells treated with somatropin alone was increased significantly although somatropin did not show any additive effect on the IgE production of anti-CD40 antibody-treated cells. The results indicate that IL-10, a Th2-type cytokine, directly affects the mature B cells that produce IgE, and that the secretion of IgE is increased by treatment with IL-10 in cells that are stimulated with anti-CD40 and IL-4 at the level of the EBV-immortalized cell line, which has already switched to IgE production. Somatropin similarly stimulates activated mature B cells to enhance their production of antigen-specific IgE without class switching, independently of IL-4 and IL-10.