In contrast to pro-inflammatory properties, the PGD2-DP axis reduces granulocyte infiltration into the colonic mucosa in the mouse model of TNBS-induced colitis and colitis-associated colorectal cancer (24, 25) These opposing roles of CRTH2 and DP in chemotaxis are explained by different usage of G proteins. The gene discussed is PTGDR2; the disease is colitis.