Prostasomes initiate lethal PE in mice via the intrinsic coagulation pathway. (A) PE was induced by intravenous infusion of PC3 cell-derived prostasomes (0.8 µg/g body weight [bw]) in WT, F12^−/−, F11^−/−, Kng1^−/−, Klkb1^−/−, and Bdkrb2^−/− mice or WT animals pretreated with ASIS (WT + ASIS; 2.5 µg/g bw). Mortality was assessed in each group of mice (n = 5-15). Animals alive 30 minutes after challenge were considered survivors. Horizontal bars represent mean values. ***P < .001 and **P < .01 vs untreated WT. (B) Prostasome challenged mice were intravenously infused with Evans blue shortly after the onset of respiratory arrest while the heart was still beating or after 30 minutes for those animals that survived. Lungs were excised, and perfusion defects were analyzed. (C) Immunohistochemical localization of fibrin deposition on sections from lungs of WT, F12^−/−, F11^−/−, and WT + ASIS-treated mice using the fibrin-specific antibody 59D8 (high magnification, lower right). Sections were counterstained with Mayer's hematoxylin (bar, 100 µm). (D) Thrombi per visual field were counted at ×10 magnification from sections such as those in C. Columns are mean ± standard error of the mean (SEM) for 35 fields. (E) Accumulation of fibrin in lungs of prostasome-challenged WT, F12^−/−, F11^−/−, and WT + ASIS mice was analyzed by immunoblotting. (F-G) Pulmonary thromboembolism model as in A induced by injection of 10 µg/g bw seminal prostasomes (F; n = 6) or 150 µg/g bw healthy male or patient prostasomes/exosomes (G; n = 5), *P < .05 vs untreated WT (F) and **P < .01 vs healthy males (G). P values were determined using 1-way analysis of variance (ANOVA); n.s., nonsignificant.