New insights into leukocyte recruitment by intravital microscopy.

Leukocyte recruitment to sites of inflammation requires adhesion to and transmigration through the blood vessel wall. Recent progress in optical equipment and new genetic and molecular tools have revealed additional steps in the leukocyte adhesion cascade beyond rolling, adhesion, and transmigration. In vivo studies using intravital microscopy (IVM) were essential for the discovery of slow rolling, postadhesion strengthening, intraluminal crawling, and different routes of transmigration. IVM revealed unique features of leukocyte recruitment in different organs. This review focuses on insights into the leukocyte adhesion cascade gained by IVM.