Binding of tissue factor pathway inhibitor (TFPI) to factor VII-activating protease (FSAP). To measure binding of TFPI to FSAP, microtiter plates were coated with purified two-chain FSAP (tcFSAP). Biotinylated TFPI was preincubated with anti-Kunitz domain 1 (K1), anti-Kunitz domain 2 (K2), anti-Kunitz domain 3 (K3), or anti-C-terminus (Cter) of TFPI, or an irrelevant antibody (50 μg mL–1), before addition to the plate. Results are expressed as percentage binding of TFPI to FSAP, where binding of TFPI, preincubated with an irrelevant antibody, to FSAP was set at 100%. Results are given as mean ± standard error of the mean (n = 4).