Fractalkine, also known as neurotactin, is a membrane-bound CX3C Chemokine. The mature protein is part of a 397aa precursor and consists of a chemokine domain of 76aa, a mucin stalk of 241aa, a putative transmembrane domain of 18aa, and an intracellular tail of 37aa. Within the chemokine domain, the first two cysteine residues are separated by 3aa (CX3C). Fractalkine message is found in high abundance in the brain, kidney, lung and heart tissues. Fractalkine is chemotactic for monocytes and other leukocytes including NK cells and may play a role in brain inflammation.