Conditional inactivation of Tie-2 in endothelial cells evokes neutrophil-dependent leakiness of microspheres. (A) Tek^lox/lox and Tek^iECKO mice received intraperitoneal injections of anti–Gr-1 or control IgG antibodies and were stimulated 24 hours later for 3 hours with IL-1β. Fluorescent microspheres were injected IV for 5 minutes, and cremaster whole mounts were stained for PECAM-1 and MRP14. Arrowheads indicate microsphere leakage. Scale bars, 40 µm (left panels), 15 µm (right panels). Quantification of microsphere leakage (B) and relative neutrophil extravasation (C) per vessel. (D) Total lung lysates of Tek^lox/lox and Tek^iECKO mice were analyzed by immunoblot for the indicated antigens. Results are representative of (A,D) or pooled from (B-C) 4 independent experiments, with 40 or 41 vessels analyzed. Data are mean ± SEM. ***P < .001, 2-way ANOVA. n.s., not significant.