GPR84 and colitis: GPR84 in hematopoietic cells appeared to play a critical role in DSS-induced colonic inflammation because both the WT and GPR84−/− hosts that received GPR84−/− BM developed a mild colitis with a significantly reduced body weight loss, lower DAI score and less mucosal damage compared with corresponding hosts receiving WT BM cells (Fig. 3a–d).