Table 1.

Specificity of factor Xa stimulation of IL-6 release by HUVEC

Additions	IL-6 release ng/ml
Factor Xa (5 μg/ml)	2.29  ±  0.36
Factor Xa denatured	<0.010
Tumor necrosis factor α (10 ng/ml)	2.3  ±  0.8
Thrombin (1 unit/ml)	2.26  ±  1.04
Transferrin (2.5 μg/ml)	0.026  ±  0.026
Cathepsin G (50 μg/ml)	0.051  ±  0.051
Urokinase (40 nM)	0.08  ±  0.08
Chymotrypsin (100 nM)	0.134  ±  0.02
	% of control
Thrombin + hirudin (0.08 unit/ml)	123  ±  6.8
Thrombin + hirudin (10 units/ml)	3.1  ±  3.1
Factor Xa + hirudin (0.08 unit/ml)	72  ±  16
Factor Xa + hirudin (10 units/ml)	92.5  ±  3.5

Resting HUVEC monolayers were incubated with the indicated concentrations of the various proteins and cultivated for 12 h at 37°C before determination of IL-6 release by ELISA. Data are the mean ± SD of two independent determinations.