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. Author manuscript; available in PMC: 2009 May 1.
Published in final edited form as: Xenotransplantation. 2008 May-Jun;15(3):191–197. doi: 10.1111/j.1399-3089.2008.00476.x

Figure 3. Pig TFPIα binds human factor Xa and inhibits human factor VIIa/TF.

Figure 3

(A), Expression vectors were constructed for full length human and pig TFPIα, modified to incorporate a FLAG epitope tag at the N-terminus and the human CD55 GPI membrane attachment signal at the C terminus. IL-3 SS = IL-3 signal sequence; HB = heparin-binding domain of TFPIα. (B), The expression vectors were transiently transfected into COS-7 cells. Similar expression of human (H, blue line) and pig (P, red line) TFPIα was demonstrated by flow cytometric analysis using an anti-FLAG antibody (vector-transfected cells = V, black line). (C), Pig TFPIα efficiently bound human factor Xa. Left panel, representative experiment showing fXa binding by transfectants expressing human (H) or pig (P) TFPIα, relative to 12.5nM recombinant human TFPI (R) (vector-transfected cells = V, no cells control = NC). Right panel, comparison of fXa binding by human and pig TFPIα (mean ± SD of 2 independent experiments). (D), Pig TFPIα neutralised human factor VIIa/TF activity as efficiently as human TFPIα (mean ± SD of 3 independent experiments; p=0.12). Under the same conditions 3nM recombinant human TFPI inhibited fVIIa/TF activity by 66% (data not shown).