Increased leukocyte adhesion in the TNF-α–stimulated mesenteric venules of Adamts13^−/− mice. Mice were treated with the inflammatory cytokine TNF-α 3.5 h before intravital microscopy. A single mesenteric venule (25–30 μm diameter) was studied per mouse. (A) Representative images are shown. Arrows indicate leukocytes adhering to inflamed endothelium. (B) Quantification of the adherent leukocytes. The number of adherent leukocytes was markedly increased in the microvenules of Adamts13^−/− compared with Adamts13^+/+ mice. In contrast, the number of leukocytes adhering in venules of Adamts13^−/−/Vwf^−/− mice was similar to Adamts13^+/+/Vwf^−/− mice, suggesting that VWF plays a role in increased leukocyte adhesion in Adamts13^−/− vessels. Data represent the mean ± SEM. Bars, 30 μm. Video 4 is available.