DPP4 and inflammatory bowel disease: The potential mechanisms (Figure 1) of DPP-4/GLP axis in the IBD may include the following: (1) GLPs promote the tissue repair of injured epithelium; (2) GLPs regulate T-cell differentiation and functions (e.g., Treg, effector T cells, and intraepithelial lymphocytes); (3) GLPs and DPP-4 regulate the function of innate immune cells such as macrophages and DCs; and (4) suppression of DPP-4 enzymatic activities by pharmacological inhibitors preserves GLP function.