Overview Introduction Leukocytes play an important role in eliminating offending agents neutrophils and macrophages are capable of destroying microbes, necrotic tissue, and foreign substances The process of leukocytes migrating from the blood vessel to tissue involves multiple steps and are mediated by adhesion molecules and chemokines margination leukocytes become redistributed closer to the vessel wall rolling leukocytes transiently attach to endothelium and then detach login to view 1 more bullet the endothelium possesses E-selectin and P-selectin login to view 3 more bullets firm endothelial adhesion mediated by integrin proteins login to view 2 more bullets migration through the vessel wall migration to tissue StepMolecule on Vasculature/StromaMolecule on Leukocyte1. Loose adhesion, rolling E-selection, P-selectinSialyl Lewis2. Tight adhesion ICAM-1LFA-1 (integrin)3. Diapedesis PECAM-1PECAM-14. Migration through ECMBacterial products, C5a, IL-8, LTB4, KallikreinVarious