T-bet signaling pathway is induced by the activation of STAT1 in IBD process and facilitates the differentiation to Th1 cells, and Th1 cells produce and secrete IFN-γ and IL-2, which repress the differentiation to Th2 cells and restrain the expressions of IL-5 and IL-13 derived from Th2 cells, leading to the disequilibrium of Th1/Th2; in addition, IFN-γ promotes macrophages to secrete large amounts of proinflammatory cytokines and exacerbates the tissue damage [58, 66–69]. Here, IL5 is linked to irritable bowel syndrome.