Effect of rPSGL-Ig on pre-existing leukocyte rolling.

(A-B) Effect on P-selectin–dependent rolling. Leukocyte rolling was allowed to develop for 30 minutes after surgical stimulation of wild-type (WT) mice. Control rolling was recorded for 1 minute followed by injection of rPSGL-Ig at the indicated dose. Effects on proportion of leukocytes rolling (A) and rolling velocity (B) were determined and compared with controls. Anti–P-selectin or PSGL-1 antibodies were injected at the end of experiments. (C-D) Effect on E-selectin–dependent rolling. P-selectin^−/− mice were stimulated for 2 hours with TNFα, after which time cremasters were prepared for intravital microscopy. Control rolling was recorded for 1 minute followed by injection of rPSGL-Ig at the indicated dose. Effects on the proportion of leukocytes rolling (C) and leukocyte rolling velocity (D) were determined and compared with controls. Anti–E-selectin antibody was injected at the end of experiments. (E) Effect on L-selectin–dependent rolling. E-selectin^−/− mice were stimulated for 6 hours with TNFα. Mice also received P-selectin blocking antibody plus 50 U heparin at the time of TNFα injection. Cremasters were prepared for intravital microscopy, and rolling was allowed to develop for a further 30 minutes. Indicated doses of rPSGL-Ig were injected at 6 hours 31 minutes, and the effects on the proportion of leukocytes rolling were determined. Anti–L-selectin antibody was injected at the end of all experiments. All experiments were repeated in at least 4 mice. Velocities of 6 leukocytes were measured for each of at least 10 observed venules. The dashed line in panels A, C, and E indicates baseline rolling. Data in panels A, C, and E are presented as mean ± standard errors of the mean (SEMs). Significant difference from baseline rolling is indicated by *P < .05 or **P < .01.