Chemokine receptors are found on a variety of cell types and meiate important functions like chemotaxis and inflammation. The receptors can be sorted based on their specific ligands (CSC. CC. CX3C, and XC) and are composed of seven transmembrane spanning regions that are coupled to G-proteins for downstream signaling.

CX3CR1

CX3CR1 is expressed by resident and alternatively activated macrophages (M2), a subset of monocytes, dendritic cells (DCs), NK cells, a subset of memory T cells, and mast cells. CX3CR1 is involved in cell recruitment during inflammation and participates in cell adhesion and extravasation from blood vessels. Its ligand is CX3CL1, also known as fractalkine or neurotactin.  In the brain, it is expressed by glial cells, which interact with CX3CL1 expressed by neurons.

XCR1

XCR1, also known as GPR5 or CCXCR1, is the only member of the “C” chemokine receptor family. XCR1 mediateds chemotaxis via binding to XCL1 and XCL2 (lymphotactin-1 and -2), and defines a subset of CD8a+ conventional dendritic cells capable of antigen cross-presentation.

Cells from collagenase-digested C5 BL/6 mouse spleen were stained with CD11c Brillliant Violet 421, CD8a APC and purified XCR1 (clone ZET, left) or purified mouse IgG2b, k isotype control (right). The cells were then stained with biotinylated anti-mouse IgG2b, followed by Sav-PE, Data shown was gated on the CD11c+ population.