IBD is an immunological disease associated with activation of CD4+ T cells in the intestines3,4 and the expression of multiple proinflammatory chemokines, including C-X-C chemokine receptor type 4 (CXCR4), which attract leukocytes into inflamed intestines in both IBD mouse models1 and patients2. This evidence concerns the gene CXCR4 and inflammatory bowel disease.