Figure 6.

The kinetics of dissociation of transiently tethered neutrophils from PNAd and its independence from PNAd or L-selectin densities. The k _off values equal the negative slope of the lines through the dissociation data. (A) Kinetics at a wall shear stress of 0.75 dyn/cm² on different low densities of PNAd. Data at the same wall shear stress on P-selectin (1) are shown for comparison. (B) Kinetics at a wall shear stress of 0.75 dyn/cm² on higher density PNAd (60 sites per μm²) in the presence of subsaturating concentrations of control mAb AD38 to CD44 or mAb DREG-56 to L-selectin at 0.3 μg/ml. The L-selectin mAb reduced tethering frequency by 70% and abolished all rolling adhesions. (C) Dissociation rate constants at different wall shear stresses, as a function of PNAd site density. At low shear stresses, when both transiently tethered and continuously rolling cells could be observed, the few transient events that occurred had the same dissociation kinetics as those derived at low densities.