Activation of FXI after LPS infusion. Mean ± SEM of FXIa levels measured in the ECA (○) and the total amount of the FXIa-FXIa inhibitor complexes (•) after LPS administration (4 ng/kg). The y-axis presents the absolute difference from the mean value at t = 0 of both the ECA and the FXIa-FXIa inhibitor complexes. TheP value indicates difference over time (P < .001 for the ECA, P < .0001 for the FXIa-FXIa inhibitor complexes).