Effect of hGPVI-Fc on platelet adhesion. Heparinized whole blood from healthy volunteers (A) or wild-type mice (B) was incubated with the indicated concentrations of hGPVI-Fc () or control IgG (▪) for 2 minutes and perfused at wall shear rates of 1000 seconds^–1 (4 minutes) over a collagen-coated surface. Mouse blood was also tested in the presence of JAQ1 (20 μg/mL). Surface area covered by thrombi is summarized in the upper panels (mean ± SD of 5 experiments per group). Control bar (B) represents blood from wild-type mice incubated with 30 μg/mL of irrelevant IgG, but similar results were also obtained with higher concentrations (not shown). Bottom panels show representative phase-contrast images taken at the end of the experiment. (*P < .05; **P < .01)