NAP-2 regulation of leukocyte recruitment and migration at sites of vascular injury. (A) C57Bl/6 (Control) mice were administered pertussis toxin (PTX; 4 µg per mouse, 2 hours prior to experiment), PAF antagonist (WEB2086 or CV-3988, 10 mg/kg), or the CXCR1/2 antagonist MSGA 8-73 (10 mg/kg, CXCR1/2 Antag) prior to needle injury of mesenteric veins. The number of firmly adherent leukocytes was quantified by using real-time DIC imaging 20 minutes postinjury (mean ± SEM; n = 3 to 4). (B) Recombinant NAP-2 (50 μg/mL) or saline (Control) were injected 20 to 30 μm upstream from the thrombus 10 minutes postinjury, and the number of firmly adherent leukocytes was quantified (mean ± SEM; n = 3). Representative DIC images following saline or NAP-2 injection are depicted (red, firmly adherent cells; yellow, rolling cells). (C) An anti–NAP-2 Ab (Alexa-546—labeled) was injected at the site of thrombus formation 15 minutes and 30 minutes postinjury. Images depict representative overlay images of NAP-2 staining (red) localized near the base of thrombi (blue outline) adjacent to the site of vascular injury. (D) The effects of PAF antagonist CV-3988 (PAF Antag), CXCR1/2 antagonist MSGA 8-73 (CXCR1/2 Antag), and inactive control (monocyte chemotactic protein1 9-76) on leukocyte directional migration at the thrombus base were examined over a 30-minute time frame by fluorescence microscopy (mean ± SEM; n = 3 to 4). The surface area of thrombi was also quantified. ns, not significant, P > .05; **P < .01.