The CC chemokine receptor 5 (CCR5) is a member of the CC-chemokine receptor family, and has the characteristic structure of a 7 transmembrane G protein-coupled receptor (GPCR). CCR5 regulates trafficking and effector functions of memory/effector Th1 cells, macrophages, NK cells, and immature dendritic cells. CCR5 and its ligands play an important role in viral pathogenesis. CCR5 represents the co-receptor for macrophage (M) and dual (T cell and M)-tropic immunodeficiency viruses. Together with the CD4 binding receptor, CCR5 plays a critical role in HIV entry into the target cells.