CXCR2 and inflammatory bowel disease: The NOD2 locus, a cluster of chemokine genes (CXCL1-3, CXCL5-6, and CXCL8), and two receptors for these chemokines (CXCR1 and CXCR2), represent examples of enhancers linked with neighboring TSSs of genes associated with IBD pathogenesis (Fig. 4a–c).