Fractalkine, also known as CX3CL1, is an atypical chemokine that was the first of a fourth chemokine motif (CX3C). It is thought to function as a T cell and monocyte chemotractant and is produced by non-haemopoietic cells. Fractalkine is made in a soluble and membrane bound form in activated endothelial cells which is thought to promote adhesion of leukocytes. Recombinant Fractalkine is a non-glycosylated Protein, containing 76 amino acids, with a molecular weight of 8.6 kDa.