Chemokine (C-C motif) ligand 5(CCL5), also known as RANTES (Regulated upon activation, Normal T cell Expressed and presumable Secreted) is a CC-chemokine that can signal through the CCR1, CCR3, CCR5 and US28 (cytomegalovirus receptor) receptors. RANTES is chemotactic for T cells, eosinophils, and basophils, and plays an active role in recruiting leukocytes in inflammatory sites. With the help of specific cytokines (i.e., IL-2 and IFN-γ) that are released by T cells, RANTES induces the proliferation and activation of certain natural-killer (NK) cells to form CHAK (CC-Chemokine-activated killer) cells. RANTES is also an HIV-suppressive factor released from CD8+ T cells. This chemokine has been localized to chromosome 17 in humans. It has the capability to inhibit certain strains of HIV-1, HIV-2 and simian immunodeficiency virus (SIV).