CCL5 (RANTES), also known as CCL5, is a 7.8 kD member of the CC family of chemokines, which is expressed in T cells and monocytes/macrophages. RANTES is strongly chemotactic for monocytes/macrophages, memory T cells, eosinophils, and induces histamine release from basophils. In a solution, RANTES can form high molecular weight aggregates that exhibit dissimilar biological activities to its dimeric form. The aggregates cause T cell and neutrophil activation while promoting HIV infection, whereas the dimeric form exhibits RANTES-induced chemotaxis and inhibits HIV infection. As T cells become activated, RANTES secretion appears to decrease.