Schematic representation of leukocyte-endothelial cell interactions during extravasation (inset). Selectin-mediated adhesion (red/pink arrows) initiates leukocyte rolling, and integrin-mediated adhesion (blue/purple arrows) stabilizes leukocyte adhesion to endothelial cells. Endothelial junction proteins (orange arrows) mediate leukocyte transmigration. Adhesion proteins (box) and protein networks assembled at the synapse between rolling leukocytes and endothelial cells (selectin- and integrin-mediated adhesion) as well as during leukocyte transmigration (JAM-1/LFA-1, CD99, and PECAM). Abbreviations: CaM, calmodulin; ERM, ezrin/radixin/moesin; MLCK, myosin light chain kinase; RAPL, regulator of adhesion and cell polarization enriched in lymphoid tissues; ROCK, Rho kinase.