Interactions of E-selectin with clathrin-coated pits of HUVECs enhance leukocyte rolling under flow. (A) Fixed neutrophils were perfused over IL-1β–stimulated HUVECs in isotonic or hypertonic medium in the absence or presence of 10 μg/mL anti-E-selectin mAb ES1 or anti-β2 integrin mAb IB4. The wall shear stress was 1 dyne/cm². The number of rolling neutrophils was measured after 4 minutes. (B,C) The mean velocity and the variance of velocity of neutrophils rolling on IL-1β–stimulated HUVECs in isotonic or hypertonic medium was measured. The data represent the mean plus or minus SEM for at least 4 experiments (**P < .01; ***P < .001, as measured by the unpaired t test).