ADAMTS13 deficiency promotes excessive leukocyte adhesion and spontaneous plaque formation in the carotid sinus. (A) Representative photomicrographs of adhering leukocytes (> 60 seconds) at the carotid sinus, a lesion-prone site, as visualized by intravital upright microscope. Endogenous leukocytes were labeled with rhodamine 6G. White lines indicate the arteries; and arrows, adherent leukocyte. Original magnification ×200. (B) Dot plot shows the number of adherent leukocytes of each genotype (N = 8/group). Each dot represents a single mouse. Horizontal bars represent mean values. (C) Representative photomicrographs of spontaneous plaque formation as visualized by intravital upright microscope. Leukocytes were labeled with rhodamine 6G. White lines indicate the arteries; arrows, adherent leukocyte; and white dotted line, the spontaneous plaque, which occluded the vessel by approximately 70% to 80% (supplemental Video 4, available on the Blood Web site; see the Supplemental Materials link at the top of the online article). (D) The percentage of mice with a spontaneous plaque at the carotid sinus (N = 10/group).