Platelet thrombus formation after laser-induced arteriolar wall injury in β3^−/− mice. (A) Nonblocking rat anti–mouse GPIbβ antibody conjugated to DyLight 649 (0.2 μg/g body weight) was infused into a wild-type (wt) or β3^−/− mouse 5 minutes before laser-induced arteriolar wall injury. Representative images of fluorescence associated with platelets (red) are shown over the course of 180 seconds after vessel injury within the context of the bright-field microvascular histology. (B) The median integrated platelet fluorescence (F_platelets) for 22-23 thrombi in 2 WT or 2 β3^−/− mice infused with the anti-GPIbβ antibody conjugated to DyLight 649 is presented over the course of 250 seconds after vessel injury.