CXCR2 and infection: To identify mechanistic bases for the different numbers of neutrophils at the site of infection, we measured the main chemokine factors for neutrophil attraction, including the CCR1 ligands CCL3 (SI Appendix, Fig. S5A), CCL4 (SI Appendix, Fig. S5B), and CCL5 (SI Appendix, Fig. S5C) and the CXCR2 ligands MIP-2/CXCL-2 (SI Appendix, Fig. S5D), KC/CXCL-1 (SI Appendix, Fig. S5E), and CXCL5 (Fig. 4C).