Heterozygous fII^WE mice exhibit no survival advantage after challenge with acute endotoxemia and modestly lower circulating APC relative to wild-type mice. (A) Kaplan-Meier survival analysis of wild-type (n = 10) and fII^WT/WE (n = 11) mice after IP injection of LPS (15 mg/kg). (B) Determination of plasma APC concentration in wild-type and fII^WT/WE mice. Plasma was collected from unchallenged (n = 3 per genotype) mice or from mice challenged with 15 mg/kg of LPS by IP injection for 2 hours (n = 6 per genotype) and 10 hours (n = 6 per genotype). Note that 2 hours after LPS challenge, wild-type mice had approximately 2-fold more APC than fII^WT/WE mice, whereas at 10 hours the differences were more modest. (C) Thrombin-antithrombin (TAT) levels in plasma of LPS-challenged (15 mg/kg) wild-type and fII^WT/WE mice (n = 6 per genotype). Note that TAT levels were higher in the wild-type plasma at both time points. *P < .05; **P < .02; ***P < .003 by Student t test.