Effect of low-dose (1 mg/kg) rPSGL-Ig treatment on the fate of rolling leukocytes.

WT mice were prepared for intravital microscopy, and surgically induced leukocyte rolling was allowed to develop for 10 minutes. After this period, leukocytes were tracked from a point of obvious attachment (as in Figure 3) through postcapillary venules to points where confident tracking could no longer proceed (ie, if vessels were too large or passed out of the viewable area. (A) Cumulative distance/time plots for individual leukocytes. Each plot shows tracks of 2 leukocytes traveling through the same vessel network before (black line) and after (gray line) low-dose (1 mg/kg intravenously) rPSGL-Ig. Rightward-facing arrows indicate leukocytes rolling out of the observable region. Downward-facing arrows indicate firm adhesion. (B) Combined fate of leukocytes traveling through multiple networks. After surgical preparation of the cremaster and a 10-minute stabilization period, mice received either rPSGL-Ig or vehicle. Multiple leukocytes were tracked through different vessel networks of n = 4 mice per treatment (control, 46 cells, ■; 1 mg/kg rPSGL-Ig, 48 cells, ░; 30 mg/kg rPSGL-Ig, 54 cells, ▪), and their fate was determined as either rollout (leaving the observable area without detachment), stick (remaining stationary for longer than 30 seconds), or break-off (detaching from the endothelium, rejoining the free circulation, and disappearing from view). **Indicates a statistically significant difference from control, P < .01. Data are presented as mean ± SEM.