Transmission electron micrographs of a carotid artery from a β3^+/+ and a β3^−/− mouse exposed to FeCl₃ demonstrate platelet masses in the β3^+/+ mouse and a platelet monolayer in the β3^−/− mouse.

The carotid artery of the β3^+/+ mouse (A-B) was fixed approximately 7 minutes after the application of FeCl₃, whereas the artery in the β3^−/− mouse (C-F) was fixed after 30 minutes. Dark-staining FeCl₃ accumulated along the internal elastic lamina and, in the wild-type artery, within the thrombus. The vessel in the wild-type mouse was occluded by thrombus composed of platelets, fibrin, and erythrocytes (A-B). Primarily a single layer of platelets adhered to FeCl₃-treated vessel wall of the in β3^−/− mouse (C-D); fibrin and residual erythrocytes were also present. In addition to attaching directly to the damaged wall, platelets accumulated in areas rich in fibrin along the β3^−/− artery (E). Along the damaged vessel in β3^−/− mouse, adherent platelets recruited leukocytes, and additional platelets attached to the luminal surfaces of the leukocytes (F).