CD4 and colitis: In an acidic microenvironment, the expression of GPR65 by immune cells regulates the inflammatory response by a myriad of differential mechanisms, such as its role in the Th1/Th17 differentiation of CD4+ T cells [100] and its role in decreasing leukocyte infiltration to the site of inflammation in mouse models of IBD and colitis-associated colorectal cancer [36].