In vivo analysis of the effect of thrombin in the absence and presence of PC-S195A on vascular leakage in response to HMGB1. Mice (n = 5, for every experiment) were given intraperitoneal injection of the proteases (100 µg/kg APC and 5 nM thrombin ± 50 µg/kg PC-S195A) in 200 µL normal saline. After 30 minutes, all mice were intravenously injected with 1% bovine serum albumin–bound Evans blue dye followed by an immediate intraperitoneal injection of HMGB1 (15 µg/g body weight). Vascular permeability was determined from the extent of extravasation of Evans blue to the peritoneal cavity as described in “Materials and methods.” *P < .05 for APC as compared with HMGB1 and for thrombin + PC-S195A as compared with thrombin only and PC-S195A only.