Growth factors and chemokines that support myeloid cell influx and expansion after infection, including M-CSF, G-CSF, MCP-1 (CCL2), MIP-1α (CCL3), MIP-1β (CCL4), KC (CXCL1) and MIP-2 (CXCL2), are also highly abundant in S. aureus infected femurs relative to mock infected femurs. This evidence concerns the gene CXCL1 and infection.