IL4 and allergic disease: JAK/STAT signaling is highly involved in the differentiation of Th cell subsets; Th1 cell differentiation is controlled by the IFN-γ/STAT1 and IL-12/STAT4 signaling pathways.178,179 Meanwhile, Th2 cell differentiation is modulated by IL-2/STAT5 and IL-4/STAT6 signaling.180,181 The differentiation of Th17 cells mainly requires the involvement of STAT3/STAT4 signaling induced by IL-6 or IL-23.182 In allergic diseases, the JAK/STAT pathway is critical for cell proliferation and differentiation.