Antiplatelet antibody-induced thrombocytopenia and thrombosis in vivo. (A) Platelet count of hFcR transgenic mice (solid line) injected with 0.5 μg/g (■) or 1.0 μg/g (▴) body weight of anti-GPIX antibody. Platelet count of WT mice injected with anti-GPIX (1 μg/g body weight) is shown as control (dashed line, ●). The platelet counts in whole blood were determined at baseline (t = 0) and every hour up to 4 hours. Results shown are percentage platelet count compared with baseline. *P < .05. **P < .01. ***P < .001. (B) Whole-body scan with a Pearl in vivo Imager of hFcR mice and WT mice 4 hours after the injection of Alexa750-labeled anti-GPIX antibody (1 μg/g body weight) LICOR, Pearl infrared chamber, software Pearl cam Version 2.0. thx indicates thorax; lvr, liver; and spln, spleen. (Insets) Representative H&E-stained histology sections of lungs isolated from WT or hFcR mice. Arrows point at fibrin and platelet-rich thrombi in the lung vasculature. Images are representative of 3 independent experiments. Scale bar represents 50 μm. The images were obtained with a Nikon Eclipse 80i microscope (Nikon) and a 40×/0.8 numeric aperture oil-immersion objective lens, imaging medium: oil, H&E staining, Spot Flex Color camera (Diagnostic Instruments), Spot Advanced Version 4.5 software (Diagnostic Instruments).