Cooperative PSGL-1 and CXCR2 signaling in neutrophils enhances adhesion in flow-restricted IVC. (A) Top, Sagittal view of B-mode ultrasonography confirms stenosis of the IVC after ligation. The cephalic and caudal directions are marked. Bar, 1 mm. Bottom, Color Doppler mode in B-mode sagittal view reveals the flow direction in the IVC around the stenosis. The blue color indicates blood flowing toward the transducer, from right (caudal) to left (cephalic). The red color indicates blood flowing away from the transducer, from left (cephalic) to right (caudal). (B) Blood flow in the IVC was quantified by pulse Doppler mode before and after ligation. (C) Representative images of CXCL1 expression (green) and adherent Ly6G⁺ neutrophils (red) in the IVC of WT mice obtained with spinning-disk intravital microscopy. PE-conjugated anti-Ly6G mAb and Fluoresbrite green beads coated with anti-CXCL1 mAb were injected IV into WT mice 1 hour before sham surgery or surgical ligation. Top, Three hours after sham surgery; middle, 15 minutes after ligation; bottom, 3 hours after ligation. Bar, 10 μm. (D) Number of rolling neutrophils per minute per microscopic field 3 hours after ligation (vertical axis). Circulating neutrophil count for each genotype (horizontal axis). (E) Quantification of endothelial surface area covered with firmly adherent neutrophils 3 hours after ligation. The data in the graphs represent the mean ± standard error of the mean (SEM) from 5 mice in each group. *P < .05.