Effects of activin A on IgE synthesis and cytokine production by human peripheral mononuclear cells.

Activin A not only stimulates the synthesis and release of pituitary follicle-stimulating hormone, but exerts various effects on haematopoietic cells, embryos, and fibroblasts. In the present study we have examined effects of activin A on IgE synthesis and cytokine production by peripheral blood mononuclear cells (PBMC) in normal humans. When PBMC were cultured in the presence of IL-4, activin A significantly augmented IgE production induced by IL-4. Activin A did not affect, however, IgE production from highly purified B cells when they were stimulated with anti-CD40 MoAb and IL-4. The fact that in the latter condition IgE synthesis was T cell- and monocyte-independent indicated that activin A does not directly influence B cells for IgE synthesis. Rather, production as well as gene expression of IL-6, which is known to enhance IgE synthesis by purified monocytes, was induced by activin A alone. In addition, activin A induced other monokines such as IL-1 and tumour necrosis factor (TNF)-alpha from monocytes. In contrast, activin A neither induced nor augmented the production of TNF-beta or interferon-gamma (IFN-gamma), both of which are known to be exclusively generated by T cells. These data indicate that activin A plays a certain role in physiological functions for monocytes in normal humans.