hTFAA inhibition of coagulation initiated by mTF. (A) Fold prolongation of clotting by hTFAA relative to no added antagonist is shown for human plasma (▴), rhesus plasma (♦) and rabbit plasma (▪). For comparison, effects of WT sTF on clotting with human plasma are also shown (⋅). Open symbols show the effect of rTFAA on clotting time with human (▵) and rabbit (□) plasma. Coagulation experiments with human plasma used human mTF to initiate clotting whereas measurements with rhesus and rabbit plasma used rabbit brain thromboplastin to initiate coagulation. In the absence of inhibitor the clotting times were 26.9 ± 1.7 seconds (human plasma), 14.2 ± 0.3 seconds (rhesus plasma), and 7.3 ± 0.5 seconds (rabbit plasma). (B) Comparison of hTFAA effects in human (⋅) and rabbit (▪) plasma. For these experiments, a standard curve relating clotting time to the concentration of relipidated human TF(1-243) (human plasma) or dilution of rabbit brain thromboplastin (rabbit plasma) was used to evaluate the apparent TF activity as a function of inhibitor concentration. The amount of initiator added was adjusted to give a clot time of 21 seconds in the absence of hTFAA. For human plasma, this clotting time was obtained with 1 nmol/L relipidated human TF(1-243). The solid lines are the result of nonlinear regression analysis using equation 1.