Microvascular platelet thrombi induce directed intravascular leukocyte conveyance in response to localized endothelial injury. (A-F) GFP or C57Bl/6 mouse mesenteric veins were subjected to needle injury with local microinjection of thrombin, and the thrombus formation and leukocyte recruitment were monitored by confocal, epifluorescence, or DIC microscopy. (A) Representative DIC and fluorescence images of thrombi (red) and leukocyte recruitment (green) in mesenteric veins of C57Bl/6 mice following repetitive injury at the indicated time postinjury. (B) Time course of leukocyte recruitment to thrombi expressed as number per unit volume (mean ± SEM; n = 4), and quantified as described in “Materials and methods” and supplemental Methods, Quantitative analysis of leukocyte recruitment and adhesion to thrombi in vivo. (C) Left panel: representative image depicting migrating leukocytes (Gr-1 Ab, green) at different positions between the margin and the center (the site of vascular injury) of a thrombus (3,3′-dihexyloxacarbocyanine iodide [DiOC6], red) 10 minutes postinjury; the inset demonstrates the polarized morphology of individual migrating leukocytes. Right panel: migration paths (dotted lines) of individual leukocytes moving from the margins of the thrombus toward the site of vascular injury (thrombus core, red shaded area). (D) Migration velocity (µm/min) of individual leukocytes determined by using ImageJ software (n = 30). (E) Images depicting the presence of leukocytes (Gr-1 Ab, green) within the three-dimensional thrombus body (upper left), taken from front, back, and lateral perspectives 30 minutes postinjury. (F) Images depicting leukocyte migration (Gr-1 Ab, green) through the Top, Middle, and Base of a representative thrombus (red, 30-mm height as schematically depicted on the upper right) at the indicated time postinjury.