Figure 4.

Challenge with Stx or histones decreases activation of protein C. The ability of human aortic endothelial cells (A,C) or renal endothelial cells (B,D) to activate protein C after 24 h challenge with Stx1, Stx2, or histones was determined on confluent monolayers with 10 nM human alpha-thrombin and 0.2 μM human protein C at 37°C. Activated protein C was quantified in cell supernatants with spectrozyme PCa substrate and converted to nM APC using a standard curve, then adjusted for cell number with Draq5 staining. Anti-histone antibody BWA3 (20 μg/mL) was added before challenge in some wells. Differences relative to media alone are shown as *p < 0.05, **p < 0.01, ***p < 0.001.