The leukocyte extravasation cascade is controlled by sequential adhesive interactions between leukocytes and ECs. This schema depicts various steps of the extravasation cascade and the adhesive molecules that are involved at each step. The neutrophil extravasation cascade involves a sequence of tethering and rolling along the endothelium, followed by firm adhesion and arrest onto the endothelium. Subsequently, neutrophils undergo lateral migration or crawling on ECs to find a permissive site for transmigration. During this step, the formation of the ICAM-1 adhesome and F-actin–rich filopodia emerging from ECs are critical prior to diapedesis. Diapedesis can occur at EC junctions (paracellular migration) or through the EC body (transcellular migration). Once they have crossed the perivascular basement membrane, neutrophils migrate into the interstitial tissue. They can also return to the blood circulation in a reverse migration process. PMN, polymorphonuclear neutrophil.