FIG. 2.

Alternative routes of leukocyte passage across the endothelium. Following β2-integrin-mediated arrest of PMN, the endothelium proactively forms an ICAM-1 enriched “cuplike” structure (transmigratory cup) comprising microvilli-like projections which surround the adherent PMN. The PMN in the transmigratory cup can take two different pathways to migrate across the endothelium. PMN can either squeeze through the intercellular clefts between endothelial cells (“paracellular” TEM) or migrate through the endothelial cell body (“transcellular” TEM). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).