Histology and immunohistochemistry with antibodies to platelets and fibrin(ogen) reveal increased platelet- and fibrin(ogen)-rich thrombi in the lungs of β3^+/+ mice injected with collagen + epinephrine as compared to β3^−/− mice.

Mice were injected with collagen + epinephrine, and 3 minutes later sections of lung tissue were stained with hematoxylin and eosin (panels A-B, 40 ×). Arrowheads point to thrombi in the pulmonary vasculature of a β3^+/+ mouse; thrombi were present in the central and peripheral fields of the lung. Fewer thrombi were present in β3^−/− mice, and, in the β3^−/− mice, the thrombi (more than 70%) tended to be confined to the periphery of the lung tissue. Immunohistochemistry demonstrated that the thrombi were composed of fibrin(ogen) (C-D) and platelets (brown staining; E-F, 40 ×; G-H, 100 ×).