Although, it is possible that the reduced susceptibility to DSS-induced colitis in mPer2m/m mice may be due to some type of immune cell dysfunction, such as NK cells and macrophages, the chimeric mouse experiments strongly suggest that the Per2 mutation in non-hematopoietic cells is responsible for the protection against DSS-induced colitis (Fig. 4). Here, PER2 is linked to colitis.