Fibrin network density correlates with cellular expression of TF activity. Factor Xa generation (○, A), prothrombinase activity (●, B), and fibrin density (x-axis) were measured in reactions with HUVECs, SMCs, TNFα-stimulated HUVECs, and fibroblasts (left to right) as described in “TF, prothrombinase activity, and activated protein C generation assays.”