Effect of 15H8 on platelet and fibrin deposition in a baboon arteriovenous shunt thrombosis model. Thrombogenic devices depicted in Figure 2 were inserted into femoral arteriovenous shunts in olive baboons as described.^9,13,14  Flow through the grafts was maintained at 100 mL per minute, producing an initial average wall shear rate of 265 s⁻¹  within the 4-mm diameter portions of the graft. (A) Platelet accumulation in the collagen-coated, silicon linker, and silicon expansion chamber segments of grafts was assessed in real time by imaging of local ¹¹¹In-labeled platelet accumulation using a GE-400T camera with NuQuest InteCam. The curves composed of closed circles (●) with error bars (±1 SD) represent mean values for 9 devices inserted into arterio-venous shunts in 2 untreated animals (control results). Individual results for 4 devices tested in the same 2 animals at least 1 hour after administration of anti-fXII antibody 15H8 (5-6 mg/kg IV) are indicated by the symbols ○, △, ▽, and ♢. (B) Endpoint determinations of total ¹²⁵I-labeled fibrin deposition during the experiments in panel A. Fibrin deposition in the collagen-coated graft segment (left panel) and silicon expansion chamber (right panel) were determined for 8 of the 9 devices inserted before animals received 15H8 (●) and for the 4 devices tested after animals received 15H8 (○). Large bars indicate mean values and smaller bars ± 1 SD (C) Plasma TAT complex measured in blood obtained at various times after graft insertion from the arteriovenous shunt upstream of the site of graft insertion for 6 of 8 control grafts (●), and the 4 grafts placed after 15H8 administration (○). Large bars indicate mean values and smaller bars ± 1 SD.