Platelet recruitment supports DVT formation in vivo. (A) Immunohistological cross sections of the IVC 48 h after DVT induction display platelet accumulation (CD41⁺) within the thrombus. Nuclei are counterstained with DAPI. Bars, 200 µm. Representative of n = 3 experiments. (B) Representative images of intravital video microscopy of blood cell recruitment taken at 6 h after DVT induction. Arrowheads: thrombi; arrows: single, adherent cells. Platelets, red (rhodamine B); leukocytes, green (Acridine orange). Bars, 100 µm. (C) Time-lapse images of the developing thrombus (arrowheads) visualized by two-photon microscopy 6 h after DVT induction. Platelets (yellow) and neutrophils (green) are recruited from the bloodstream (blue) to the vessel wall (red; see also Video 8). (D) Platelet–leukocyte interaction was determined by intravital microscopy in C57BL/6 and IL4-R/Iba mice after 6 h of flow restriction. Bars: (left) 50 µm; (right) 100 µm. The right panel shows quantification of colocalization of leukocytes and platelets in WT (n = 5) and IL4-R/Iba mice (n = 4). Data are shown as mean ± SEM. (E) Representative images obtained by video microscopy 6 h after DVT induction in IL4-R/Iba and control animals (n = 3 per group). Platelets are pseudocolored in red (DyLight488-labeled GPIbβ antibody) and leukocytes in green (Acridine orange). Bars, 100 µm. (F) Representative images taken by intravital microscopy of WT mice 1 h after induction of venous (left) and 5 min after arterial (right) thrombosis. Arrows show platelet aggregate formation. Leukocytes are fluorescently labeled (green) by i.v. application of Acridine orange. Bars, 50 µm. (G) Quantitative analysis of platelet (plt) and leukocyte (lcs) accumulation (as percentage of WT controls) in IL4-R/Iba (n = 3) and WT mice (n = 5). Data are shown as mean ± SEM. (H) Thrombus weight at 48 h after DVT induction in C57BL/6 (n = 8) and IL4-R/Iba mice (n = 5). Dots represent individual experiments; lines show the mean of each group.