CXCL9 and cytomegalovirus infection: In murine cytomegalovirus infection [25] and in Toxoplasma gondii infection [26], early release of CCL3 and CCL4 from APCs is vital for the influx of NK cells into affected tissues, and these cells are an important source of IFN-γ, which induces macrophages and dendritic cells to secrete CXCL9 and CXCL10 [27].