Shown is the induction by IL-2 of IL-12Rβ2 to promote Th1 cell differentiation, of IL-4Rα to promote Th2 cell differentiation, and of IL-2Rα to promote Treg cell differentiation. Conversely, IL-2 represses expression of gp130 (and IL-6Rα) while inducing T-bet (not shown) to repress Th17 cell differentiation. IL-2 is also a repressor of Tfh differentiation based on its repression of BCL6 expression. Finally, IL-2 promotes the differentiation, expansion, and the cytolytic activity of cytotoxic T cells.