Rolling of WT and ΔCD leukocytes on P-selectin in vivo and in vitro. (A) Leukocyte rolling flux fractions in venules of cremaster muscle from WT and ΔCD mice subjected to trauma to mobilize P-selectin to the endothelial cell surface. (B) Leukocyte rolling velocity distributions in venules of cremaster muscle from WT and ΔCD mice subjected to trauma. The cumulative histograms of rolling velocities of the indicated number of leukocytes are depicted. The mean rolling velocities (V_avg) are also shown. (C) Velocities of WT neutrophils suspended in buffer, WT plasma, or ΔCD plasma rolling on P-selectin at a wall shear stress of 1 dyne/cm². (D) Flow cytometric analysis of PSGL-1 expression on ΔCD leukocytes and on WT leukocytes treated with OSGE (WT-tr). Leukocytes were incubated with PE-conjugated anti–PSGL-1 2PH1, which recognizes an epitope within the N-terminal P-selectin–binding region. (E) Number of WT-tr or ΔCD neutrophils rolling on P-selectin (235 sites/μm²) captured on the floor of a flow chamber at the indicated wall shear stress. (F) Velocities of WT-tr or ΔCD neutrophils rolling on P-selectin at the indicated wall shear stress. (G) Representative membrane tethers, marked by arrowheads, extending from the trailing edge of a WT or ΔCD neutrophil rolling on P-selectin at a wall shear stress of 1 dyne/cm². Flow is from right to left. Bar represents 1 μm. In panels A and B, injection of 30 μg anti–P-selectin mAb RB40.34 detached all rolling leukocytes, confirming the P-selectin–dependency of rolling. In panels C and in E-G, rolling was eliminated by anti–PSGL-1 mAb 4RA10 or anti–P-selectin mAb RB40.34. The data represent the mean plus or minus SEM from at least 3 experiments.