Vascular pathology in FcγRIIA/hPF4 mice injected with anti-hPF4/heparin antibody and heparin.

Hematoxylin/eosin–stained lung sections from KKO/heparin–treated FcγRIIA/hPF4 mice show intravascular fibrin precipitation and thrombus formation in arterioles and capillaries, as indicated by arrows (panel A, 100 ×), while lung sections from FcγRIIA/hPF4 mice injected with KKO/saline (panel B, 100 ×) show no evidence of thrombus formation. Thrombi in the lungs (panel C, 40 ×; panel E, 20 ×; arterial and venous, respectively) were rich in hPF4, as shown by immunostaining with RTO, a monoclonal antibody specific for hPF4, while staining with an isotype control antibody was negative (panel D, 40 ×; panel F, 20 ×; arterial and venous, respectively).