FXIIa inhibition protects mice from prostasome-induced PE. (A) Real-time thrombin formation in murine platelet-free plasma stimulated with PC size synthetic polyP (LC polyP, 100 µg/mL) in the absence or presence of increasing concentrations of anti-FXIIa antibody 3F7 (n = 3). Molar antibody concentrations are relative to plasma FXII (375 nM). (B) Mortality associated with intravenous injection of PC3 cell prostasomes (0.8 µg/g bw) in WT mice pretreated with saline or 3F7 (4.5 µg/g bw) was assessed in each group (n = 6); animals still alive at 30 minutes after challenge were considered survivors. ***P < .001 vs saline, unpaired Student t test. (C) Mice challenged with prostasomes were intravenously infused with Evans blue shortly after respiratory arrest while lungs were still perfused. Excised lungs show perfusion defects in red. (D) Sections from lungs of saline- and 3F7-treated WT mice were analyzed for fibrin by immunohistochemistry with 59D8 antibody and counterstained with Mayer’s hematoxylin; bar, 100 µm. (E) Thrombi per visual field were counted at ×10 magnification from sections such as those in D. ***P < .001 vs saline, unpaired Student t test. Columns are mean ± SEM for 35 fields. (F-G) 3F7 treatment does not impair hemostatic capacity. (F) Tail bleeding times and (G) total hemoglobin loss assessed by hemoglobin absorbance at λ = 575 nm was determined in saline- and 3F7-infused mice. Mean ± standard deviation, n = 10.