Blockade of endothelial VWF prevents microsphere leakage during neutrophil transmigration. (A) C57BL/6 mice received anti–Gr-1 antibodies or control (Ctrl) IgG and were injected IV with VWF-blocking or control antibodies 24 hours later. Five minutes later, local inflammation was induced by intrascrotal IL-1β injection. Fluorescent microspheres were injected IV 4 hours later, and cremaster whole mounts were prepared and stained for PECAM-1 and MRP14 5 minutes later. Arrowheads indicate microsphere leakage. Scale bars, 40 µm (left panels), 15 µm (right panels). Microsphere leakage (B) and neutrophil extravasation (C) in experiments as depicted in (A) were quantified and normalized to vessel surface. Results are representative of (A) or pooled from (B-C) 5 independent experiments, with 50 vessels analyzed. Data are mean ± SEM. *P < .05, ***P < .001, 1-way ANOVA.