CX₃C-chemokine receptor 1 (CX₃CR1) is a 368 amino acid (aa) protein that contains seven-transmembrane domains and belongs to the family of G protein coupled receptors¹.

CX₃CR1 has a central role in adhesion and chemotaxis through binding to its ligand, fractalkine CX₃C chemokine ligand 1, (CX₃CL1). The major role of CX₃CR1 in immune cells is to recognize and enter inflamed tissue according to CX₃CL1 gradient and initiate the innate immune system². The receptor-ligand axis also mediates the crosstalk between glial cells and neurons by direct or indirect ways in the central nervous system (CNS)³. Expression and interaction of CX₃CR1 with CX₃CL1 is related to many diseases among which are asthma, cancer and gut infections (reviewed in 4).

Both CX₃CL1 and CX₃CR1 are expressed throughout the body. However, their expression is highly cell type-specific depending on organs and tissues. In the brain, CX₃CL1/CX₃CR1 signaling can modulate the production of cytokines by microglia cells. It has been reported that CX₃CL1/CX₃CR1 signaling is associated with Alzheimer's disease⁵. In the liver, CX₃CR1 is expressed in monocytes, CD8⁺ T cells, and natural killer (NK) cells. Besides immune cells, it is highly expressed at inflammatory sites⁴.