Interactions of neutrophil-derived OSM with gp130-containing receptors on endothelial cells enhance P-selectin–dependent rolling in mouse postcapillary venules. (A) Rolling flux fraction of leukocytes in postcapillary venules of trauma-stimulated cremaster muscle from WT mice with or without injection of the indicated mAb. (B) Representative flow cytometric data of intracellular OSM expression in Ly6G⁺ neutrophils from WT mice, Osm^−/− mice, irradiated Osm^−/− mice transplanted with bone marrow from WT mice, or irradiated WT mice transplanted with bone marrow from Osm^−/− mice. (C-D) Rolling flux fraction and rolling velocity of leukocytes in postcapillary venules of trauma-stimulated cremaster muscle from the indicated genotype. (E) Representative fluorescent images of injected labeled neutrophils rolling in postcapillary venules of trauma-stimulated cremaster muscle of Osm^−/− mice. Venular endothelial cells were labeled with Alexa Fluor 488–conjugated anti-CD31 mAb, outlined by the blue dashed line. The images depict distances rolled by the circled cells in a 2-second interval. The arrow indicates the path of each rolling cell. Top, Injected WT neutrophils (red); middle, injected Osm^−/− neutrophils (blue); bottom, injected 1:1 mixture of WT (red) and Osm^−/− (blue) neutrophils. Scale bar, 10 μm. (F-G) Rolling flux fraction and rolling velocity of injected labeled cells. (H, left) Representative images of Fluoresbrite Red microspheres coated with anti-gp130 mAb or isotype control IgG adhering to endothelial cells in trauma-stimulated venules of cremaster muscle from tamoxifen-treated WT or gp130^flox/floxVECad-Cre-ER^T2 mice. To block rolling of leukocytes, which also express gp130, anti-mouse PSGL-1 mAb 4RA10 was injected 1 hour before exteriorization of the cremaster muscle. (H, right) Quantification of the covered area of adherent microspheres with digital image analysis software. The data represent the mean ± standard error of the mean (SEM) from 10 venules from 5 mice. Scale bar, 10 μm. (I-J) Rolling flux fraction and rolling velocity of leukocytes in postcapillary venules of trauma-stimulated cremaster muscle from tamoxifen-treated WT or gp130^flox/floxVECad-Cre-ER^T2 mice, with or without preinjection of blocking anti–P-selectin mAb. The data in panels B and H are representative of 5 experiments. The data in panels A,C-D,F,I-J represent the mean ± SEM from 10 to 20 venules from 4 to 8 mice in each group. **P < .01.