CD4 and colitis: In spite of PGE2 contributing to the initiation of M2 macrophage polarization, we speculate that Th2 cytokines, such as IL-4, may further facilitate M2 polarization in the late stage of colitis in miR-155−/− mice, as miR-155−/− CD4+ T cells were intrinsically more prone to polarize toward Th2 cells with amplified Th2 cytokine production (12).