Effect of fXIa on thrombin generation in fXI-deficient plasma. Thrombin generation in plasma supplemented with (A) vehicle or (B) 30 nM fXI. Coagulation was initiated with (1) 300, (2) 30, (3) 3.0, (4) 0.3, or (5) 0.0 pM fXIa. Note that curves 4 and 5 in panel A, and curve 5 in panel B, are essentially flat lines (ie, no thrombin generated).