CX3CR1 and its chemokine ligand fractalkine (CX3CL1) have been implicated in the recruitment of mononuclear phagocytes to sites of inflammation and injury (7, 10, 11) and play roles in the pathogenesis of several inflammatory conditions, including atherosclerosis (12, 13), neuropathic pain (14), and asthma (15). This evidence concerns the gene CX3CL1 and asthma.