Fractalkine is a transmembrane protein and chemokine involved in the adhesion and migration of leukocytes. The protein encoded by this gene is a receptor for fractalkine. The encoded protein also is a coreceptor for HIV-1, and some variations in this gene lead to increased susceptibility to HIV-1 infection and rapid progression Receptor for the C-X3-C chemokine fractalkine (CX3CL1) present on many early leukocyte cells; CX3CR1-CX3CL1 signaling exerts distinct functions in different tissue compartments, such as immune response, inflammation, cell adhesion and chemotaxis. CX3CR1-CX3CL1 signaling mediates cell migratory functions. Responsible for the recruitment of natural killer (NK) cells to inflamed tissues. Acts as a regulator of inflammation process leading to atherogenesis by mediating macrophage and monocyte recruitment to inflamed atherosclerotic plaques, promoting cell survival. Involved in airway inflammation by promoting interleukin 2-producing T helper (Th2) cell survival in inflamed lung. Involved in the migration of circulating monocytes to non-inflamed tissues, where they differentiate into macrophages and dendritic cells. Acts as a negative regulator of angiogenesis, probably by promoting macrophage chemotaxis. Plays a key role in brain microglia by regulating inflammatory response in the central nervous system (CNS) and regulating synapse maturation. Required to restrain the microglial inflammatory response in the CNS and the resulting parenchymal damage in response to pathological stimuli. Involved in brain development by participating to synaptic pruning, a natural process during which brain microglia eliminates extra synapses during postnatal development. Synaptic pruning by microglia is required to promote the maturation of circuit connectivity during brain development.AIDS. Four transcript variants encoding two different isoforms have been found for this gene.