Fractalkine (CX3CL1), a member of the intercrine delta family, is also known as C-X3-C motif chemokine 1, CX3C membrane-anchored chemokine, neurotactin and small-inducible cytokine D1, which can be cleaved into processed fractalkine. The soluble form of CX3XL1 is chemotactic for T-cells and monocytes, but not for neutrophils. The membrane-bound form promotes adhesion of those leukocytes to endothelial cells. CX3CL1 may also play a role in regulating leukocyte adhesion and migration processes at the endothelium. Furthermore, CX3CL1 can bind to CX3CR1.