CXCR1 (also known as IL-8RA) is a Gi/o-coupled GPCR expressed on neutrophils, CD8(+) T cells, and intestinal epithelial cells (Murphy, 1997; Sturm et al., 2005; Takata et al., 2004). CXCR1 binds with high affinity to the chemokine interleukin-8 (IL-8) and much lower affinity to GROα, whereas a related receptor, CXCR2, binds with equal affinity to IL-8 and GROα (Hall et al., 1999). CXCR1 has been proposed to be the primary regulator of neutrophil response to IL-8 in sepsis (Cummings et al., 1999). Antagonists of CXCR1 and CXCR2 have been developed and display efficacy in animal models of reperfusion injury (Bertini, et al., 2004; Kaneider et al., 2005). Chemicon's cloned human CXCR1-expressing cell line is made in the Chem-1 host, which supports high levels of recombinant CXCR1 expression on the cell surface and contains high levels of the promiscuous G protein Gα15 to couple the receptor to the calcium signaling pathway. Thus, the cell line is an ideal tool for screening for antagonists of interactions between CXCR1 and its ligands.