Microkinetics of neutrophil rolling is regulated by LFA-1. (A) The instantaneous velocity of rolling neutrophils was quantitated as the distanced traversed by individual neutrophil centroids every 0.250 second for the length of time the neutrophil remained in the field of view. Data are representative of the average response of 30 individual neutrophils from 6 to 8 separate experiments. (B) LFA-1 activation regulates neutrophil rolling dynamics. The average rolling velocity and standard deviation from the mean velocity for neutrophils on IL-1β activated HUVECs were quantitated at 0.250-second intervals for the length of time an individual rolling neutrophil remained in the field of view. Data represent mean ± SEM for 30 neutrophils in 4 to 6 separate experiments. ^**Significance in velocity between IC487475 and both TS1/22 (P < .01) and BIRT (P < .001). #Significance in deviation between IC487475 and both TS1/22 (P < .01) and BIRT (P < .001).