ABSTRACT
This chapter explores the role of the vascular endothelium in leukocyte trafficking. It focuses on some of the characteristics of the endothelium that lines vessels in nonlymphoid tissues at sites of inflammation. It discusses the molecular organization of the endothelial surfaces, such as induction and apical expression of leukocyte adhesion molecules, endothelial cell-to-cell lateral junctions, and their relationship to blood leukocyte trafficking through these surfaces to gain passage into the extravascular space. Localized leukocyte accumulation is the cellular hallmark of inflammation. Much of the current information on leukocyte transmigration is based on findings from patients with rare, heritable diseases that result in a general defect in the inflammatory response. Leukocyte transmigration, which is also termed extravasation, emigration, or diapedesis, across nonlymphoid, peripheral vascular endothelium during inflammation usually occurs at the level of postcapillary and collecting venules, where the endothelial junctions are least specialized.
