FIG. 2.

JAK/STAT signaling is critical for the differentiation of CD4+T-cells. Naive CD4+Th cells differentiate into various distinct functional subsets depending on the cytokines they encounter. Specifically, Th1 cell differentiation is induced by IL-12 through activation of JAK2/TYK2 and STAT4, Th2 cell differentiation is induced by IL-4 activation of JAK1/3 and STAT6, while Th17 cell differentiation requires IL-6 and IL-23, which signal through JAK1/2 and STAT3, as well as IL-1β. IL, interleukin; Th, T helper.