Cytokine regulation of immunoglobulin isotype switching and expression.

Several cytokines have been shown to regulate the expression of specific isotypes by affecting either the frequency of isotype switching or allowing maturation of precommited precursors. IL-4 enhances the production of IgG1 and is required for IgE production in vitro and in vivo. Evidence has been provided that Il-4 acts by enhancing switching to IgE, and perhaps IgG1. IFN-gamma was shown to stimulate the secretion of IgG2a in concentrations at which it inhibits IL-4 induced production of IgG1 and IgE. IL-5, on the other hand, appears to stimulate maturation. Recent evidence suggests that transforming growth factor-beta induces switching to IgA, despite the inhibitory activity on other isotypes.