Integrin LFA-1 regulates immune cell adhesion and trafficking by binding to ICAM-1 upon chemokine stimulation. Integrin-mediated clutch formation between extracellular ICAM-1 and the intracellular actin cytoskeleton is important for cell adhesion. We applied single-molecule tracking analysis to LFA-1 and ICAM-1 in living cells to examine the ligand-binding kinetics and mobility of the molecular clutch under chemokine-induced physiological adhesion and Mn 2þ -induced tight adhesion. Our results

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... how a transient LFA-1-mediated clutch formation that lasts a few seconds and leads to a transient lowermobility is sufficient to promote cell adhesion. Stable clutch formation was observed for Mn 2þinduced high affinity LFA-1, but was not required for physiological adhesion. We propose that fast cycling of the clutch formation by intermediate-affinity integrin enables dynamic cell adhesion and migration.