Chemokine (C-C motif) ligand 5 (CCL5) also known as RANTES, is a chemotactic cytokine. It is chemotactic for T cells, eosinophils, and basophils, and plays an active role in recruiting leukocytes into inflammatory sites. With the help of particular cytokines (i.e., IL-2 and IFN-γ) that are released by T cells, CCL5 also induces the proliferation and activation of certain natural-killer (NK) cells to form CHAK (CC-Chemokine-activated killer) cells. It is also an HIV-suppressive factor released from CD8 T cells. Recently, the RANTES protein has been engineered for in vivo production by Lactobacillus bacteria, and this solution is being developed into a possible HIV entry-inhibiting topical microbicide.