Epithelial ICAM-1 and ICAM-2 regulate the egression of human T cells across the bronchial epithelium

ABSTRACT Egression of inflammatory cells from the lung interstitium into the airway lumen is critical for the resolution of inflammation, but the underly-ing mechanisms of this egression are unclear. Here, we use an in vitro system, in which human T cells migrate across a bronchial epithelial monolayer, to investigate the molecules involved. We show that although inhibition of T-cell LFA-1 blocks egression by 75! 5.6 % (P<0.0001), inhibition of the LFA-1-ligand ICAM-1 on the epithelium only inhibits by 52.7! 0.06 % (P"0.0001). We, therefore, looked for other epithelial ligands for LFA-1 and demonstrate that ICAM-2, but not ICAM-3, is expressed on the bronchial epithelium. Blocking ICAM-2 inhibits egression by 50.95! 10.79 % (P"0.04), and blocking both ICAM-1 and ICAM-2 inhibits egression by 69.6! 5.2 % (P&lt