mAbs against CD44 (IM7 and KM81) and Gr-1 (RB6-8C5) deplete granulocytes in the circulation and exert similar effects on the rolling/adhesion behavior of leukocytes. (A) Peripheral blood neutrophil counts in WT mice before and 1 and 24 hours after intravenous administration of: (top left) 200 μg () control rat IgG, (●) IM7, or (○) KM81; and (top right) 40 μg () rat IgG, (●) IM7, or (▲) anti–Gr-1 (n = 9 mice/group, *P < .05). (B) Comparison of the effects of IM7 and anti–Gr-1 mAbs (both at 40 μg) on the rolling and adhesion of leukocytes in the inflamed synovial vessels. The results are expressed as ratios of changes observed after treatment with specific mAbs vs control rat IgG (n = 8 mice/group, *P < .05). (C) IVM snapshots of leukocytes in a synovial venule before (0 minutes, baseline, left panel) and 5 minutes after intravenous injection of 40 μg anti–Gr-1 mAb (right panel). Arrows indicate bright rolling cells (left panel) that disappeared after anti–Gr-1 injection (right panel), and dotted lines encircle adherent cells that underwent changes in morphology (became hairy/disheveled in appearance) after anti–Gr-1 treatment.