Leukocyte-endothelial cell interactions.

The movement of leukocytes from the blood circulation into organized lymphoid tissues or sites of inflammation requires cooperative interactions between signaling and adhesion molecules. Selectins mediate the initial rolling contacts of leukocytes with the endothelium. Following leukocyte activation, integrins strengthen adhesion and then direct migration beneath the endothelium. Unique combinations of signaling and adhesion molecules may regulate the subsets of leukocytes that are recruited into specific tissues.