CXCL9 and cancer: While the egress of Th1 and NK cells from intestinal lymphoid tissues and their entrance into the bloodstream are driven by the S1PR1/5 receptors and their ligand S1P, the exit from the systemic circulation of Th1 and NK cells and their infiltration of cancers are driven by CXCR3, a receptor expressed by T cells (44, 45) and NK cells (46), and its ligand CXCL9, which is induced or upregulated by IFN-γ (47, 48).