Recalcified whole blood (A, D), pooled human plasma (PPP; B, E) or coagulation-factor depleted plasma (C, F) was incubated with indicated FXI function blocking antibody, FXII inhibitor (CTI) or direct thrombin inhibitor (hirudin). aPTT (A–C) or PT (D–F) was recorded as described in Methods. *indicates significantly different, p < 0.05, clotting time vs. vehicle (mean±SEM).