Intraluminal crawling versus interstitial neutrophil migration during inflammation.

Site-directed trafficking of polymorphonuclear neutrophils (PMN) to their target regions within the tissue is an important prerequisite for efficient host defense during the acute inflammatory response. This process requires intraluminal crawling of PMN on the activated endothelial cells to their extravasation sites. Upon transendothelial diapedesis, PMN migrate in the interstitial tissue to sites of inflammation. These crucial steps within the recruitment cascade are defined as intraluminal crawling and interstitial migration. In this review, we will focus on the molecular mechanisms that control and fine-tune these migratory processes and discuss the role of adhesion molecules of the β2 integrin (CD11/CD18) family for these cellular functions.