CCL2 and infection: Each macrophage population under investigation appeared to produce a distinct chemokine pattern in the absence of infection: untreated macrophages low MCP-1/low IL-8, macrophages treated with IFN-γ high MCP-1/low IL-8, macrophages treated with GM-CSF moderate MCP-1/high IL-8, and macrophages treated with IFN-γ and GM-CSF high MCP-1/high IL-8.