CCL5 is an 8kDa protein classified as a chemotactic cytokine or chemokine. CCL5 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[citation needed]. This chemokine has been localized to chromosome 17 in humans.RANTES was first identified in a search for genes expressed "late" (3–5 days) after T cell activation. It was subsequently determined to be a CC chemokine and expressed in more than 100 human diseases. RANTES expression is regulated in T lymphocytes by Kruppel like factor 13 (KLF13). RANTES, along with the related chemokines MIP-1alpha and MIP-1beta, has been identified as a natural HIV-suppressive factor secreted by activated CD8+ T cells and other immune 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.