Colitis scores in Cdcs1+/+Il10ra−/−Ccr2−/− mice are significantly higher than either wild-type mice or those that lack CCR2 alone (Cdcs1+/+), which do not develop histologic signs of colitis, and there are likewise significant increases in the number of colonic macrophages isolated from Cdcs1+/+Il10ra−/−Ccr2−/− mice compared to these control strains. The gene discussed is CCR2; the disease is colitis.