Figure 1

Increase in endothelial surface TF activity in response to IL-1β and dependence of IL-1β induced vascular permeability on tissue factor expression. Confluent EC monolayers were incubated for 3 hours with increasing concentrations of IL-1β and a single step coagulation assay performed to measure TF activity. A rapid increase of TF activity was observed at IL-1β of 100 pg/ml to rapidly plateau at 1 ng/ml or above (a). At concentrations of 0.1 ng and 1.0 ng/ ml, IL-1β strongly induced vascular permeability only in the presence of Factor VIII-deficient plasma and there was a modest increase in vascular permeability without plasma (b). All experiments were conducted in triplicate.