● ● ● VASCULAR BIOLOGY Comment onWoodfin et al, page 6246

Francisco Sánchez-Madrid and Olga Barreiro NATIONAL CENTER OF CARDIOVASCULAR RESEARCH, MADRID Themolecular regulation of the specific sets of endothelial receptors that mediate leukocyte diapedesis is not fully understood. Using elegant adoptive transfer ex-periments with cells from genetically deficient mousemodels, in this issue ofBlood Woodfin and colleagues show that the junctional molecules ICAM-2, JAM-A, and PECAM-1mediate neutrophil transmigration in a stimulus-dependentmanner and define how this ability is regulated by the activated endothelium. Leukocyte transmigration across vascularendothelium is a key event in the inflamma-tory response.The extravasationprocess is or-chestratedby the concerted action of cellular adhesion receptors and chemotactic factors, and requires cell shape changes in both leukocytes and endothelial cells. For both cell types, it is an active process and controls the rapid recruitment of leukocytes to inflammatory fociwithout alter