Leukocyte migration to the site of endothelial injury is greatly attenuated in NAP-2^−/− mice. (A-C) C57Bl/6 wild-type (WT) and NAP-2^−/− mice were subjected to mesenteric venous needle injury with local microinjection of thrombin. Thrombus formation and leukocyte recruitment at the thrombus base were monitored for 20 minutes by using fluorescence and DIC microscopy. (A) The number of leukocytes migrating toward the site of vascular injury was quantitated in C57Bl/6 (WT) and NAP-2^−/− mice (mean ± SEM; WT group, n = 15 injuries; NAP-2^−/− group, n = 15 injuries). The surface area of thrombi was also quantified. (B) Representative fluorescence images depicting leukocyte–thrombus interactions (leukocytes: Gr-1 Ab, green; platelets: DiOC6, red) in C57Bl/6 (WT) and NAP-2^−/− mice; the insets demonstrate the marked reduction in shape-changed and migrating leukocytes in NAP-2^−/− mice. (C) The number of leukocytes interacting with the thrombus margin was quantitated 20 minutes postinjury in C57Bl/6 (WT) and NAP-2^−/− mice. (D) Platelet lysates from C57Bl/6 (WT) and NAP-2^−/− mice were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting analysis for NAP-2, CXCL1, and CXCL5, and representative blots from 1 of 3 independent experiments are shown. ns, not significant; ***P < .001.