Stromal-Derived Factor (SDF-1) is a chemoattractant active on T-lymphocytes and monocytes, but not neutrophils. This cytokine activates the C-, Xenopus/Amphibian,-C chemokine receptor C, Xenopus/Amphibian,CR4 to induce a rapid and transient rise in the level of intracellular calcium ions and chemota, Xenopus/Amphibian,is. SDF-1-alpha (3-67) and SDF-1-beta (3-72) show a reduced chemotactic activity. Binding to cell surface proteoglycans inhibits formation of SDF-1-alpha (3-67),Porcinereserving the activity of SDF-1 on local sites. SDF-1 acts as a positive regulator of monocyte migration and a negative regulator of monocyte adhesion via the Lyn kinase. SDF-1 stimulates migration of monocytes through its receptor, C, Xenopus/Amphibian,CR4, and decreases monocyte adherence to surfaces coated with ICAM-1, a ligand for beta-2 integrins.