CXCR7, also known as RDC1, belongs to a subgroup of C-X-C chemokine receptors, which are part of a large protein family of G protein-coupled receptors (GPCR). CXCR7 binds with high-affinity to CXCL12/SDF-1 and CXCL11/I-TAC, which regulates the trafficking and activation of leukocytes. It is also a co-receptor for the entry of HIV-1. Binding of ligand to CXCR7 induces proliferation and migration of immature neurons, glia and their precursors. CXCR7 expression occurs on a wide variety of tissues and cells including monocytes, B cells, T cells and mature dendritic cells. Surface expression of CXCR7 was also reported to be on tumor cells, activated endothelial cells, fetal liver cells, and few other cell types.