FVL reduces the TFPI-dependent activation threshold for FXa-initiated thrombin generation in PRP. Thrombin generation was initiated in PRP, containing FV (black) or FVL (gray), with 5 to 100 pM FXa and 20 μg/mL collagen, in the absence (lines) or presence (dashes) of 50 nM anti-K2. Experiments were performed using 5 each of FV and FVL donors. Shown are representative thrombin generation curves from a single FV donor and a single FVL donor.