CD4 and colitis: Although the IL-23/IL-17 axis is known as an essential pathway of CD4+Th17 cells in the IBD model [39] and validated with experimental models of colitis [21,40], our data demonstrated that TIAM2S-mediated IL-23 activation results in IL-17 secreting CD8+ T cell expansion, which also plays a pathogenic role in chronic colonic inflammation.