CYP24A1 and Chronic colitis: Although CD4+CD25− T cell transfer model mice are frequently used as a preclinical model for IBD, our study has an added advantage as we used this chronic colitis model to compare the efficacy of established drug treatments, namely 5-ASA and PSL, with that of hCA I. Mice were administered hCA I or established drugs (5-ASA and PSL) and colitis was induced (Fig. 5A).