Deficiency in FXII or FXI impairs collagen-dependent thrombus and platelet procoagulant activity. Blood from FXII^−/− or FXI^−/− mice or corresponding wild types was flowed over collagen under coagulant condition for 4 minutes (Figure 5). Blood was pretreated with JAQ1 mAb (40 μg/mL), as indicated. Thrombi were poststained with OG488-annexin A5. (A) Representative phase-contrast and fluorescent images (175 × 225 μm). (B left panel) Surface area covered by thrombi (□) and annexin A5 fluorescence (■). (Right panel) Frequency distribution of small and large platelet thrombi (estimated number of platelets per feature indicated in box). Mean ± SEM; n = 5-7; *P < .05 vs corresponding wild type; #P < .05, χ² test.