CXCR2 is a 7-transmembrane G protein–coupled receptor that is activated by CXC chemokines containing the ELR (Glu-Leu-Arg) motif, including murine CXCL1 (keratinocyte-derived chemokine; KC) CXCL2 (macrophage inflammatory protein 2; MIP-2), CXCL3 (DC inflammatory protein-1; Dcip1) and CXCL5 (LIX). CXCR2 is expressed on neutrophils, keratinocytes, mast cells, eosinophils, macrophages, and lung endothelial cells (1-3). Homing of mast cell progenitors (MCps) to the mouse small intestine involves CXCR2, vascular cell adhesion molecule-1 (VCAM-1), and the interaction of alpha4beta7 integrin with mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) (4). In addition, CXCR2 regulates endothelial VCAM-1 expression, MCp migration and the levels of intraepithelial MC in the lung of aerosolized, antigen-challenged mice (5).