Priming for T helper type 2 differentiation by interleukin 2-mediated induction of interleukin 4 receptor α-chain expression

Interleukin 4 (IL-4) drives T helper type 2 differentiation, whereas IL-2 augments Il4 chromatin accessibility. Leonard and colleagues now find that IL-2 also maintains the expression of Il4ra and other genes in T helper type 2–committed cells. T helper type 2 (T H 2) cells are essential for humoral immunity and host defense. Interleukin 4 (IL-4) drives T H 2 differentiation and IL-2 augments the accessibility of Il4 chromatin. Here we demonstrate that IL-2, by inducing binding of STAT5 to the Il4ra locus, which encodes IL-4 receptor α-chain (IL-4Rα), was essential for inducing and maintaining IL-4Rα expression. Although IL-4 induced IL-4Rα expression, T cell receptor–induced IL-4Rα expression was normal in Il4 −/− cells but was much lower in Il2 −/− cells. Notably, forced IL-4Rα expression restored the T H 2 differentiation of Il2 −/− cells. Moreover, genome-wide mapping by chromatin immunoprecipitation coupled with sequencing showed broad interaction of the transcription factors STAT5A and STAT5B with genes associated with T H 2 differentiation. Our results identify a previously unappreciated function for IL-2 in 'priming' T cells for T H 2 differentiation and in maintaining the expression of Il4ra and other genes in T H 2-committed cells.