Interferon-gamma and B cell stimulatory factor-1 reciprocally regulate Ig isotype production

Gamma interferon (IFN-gamma) and B cell stimulatory factor-1 (BSF-1), also known as interleukin-4, are T cell-derived lymphokines that have potent effects on B cell proliferation and differentiation. They are often secreted by distinct T cell clones. It is now shown that IFN-gamma stimulates the expression of immunoglobulin (Ig) of the IgG2a isotype and inhibits the production of IgG3, IgG1, IgG2b, and IgE. By contrast, BSF-1 has powerful effects in promoting switching to the expression of IgG1 and IgE but markedly inhibits IgM, IgG3, IgG2a, and IgG2b. These results indicate that BSF-1 and IFN-gamma as well as the T cells that produce them may act as reciprocal regulatory agents in the determination of Ig isotype responses. The effects of IFN-gamma and BSF-1 on isotype expression are independent.