CHO cells transfected with the GPIb-IX-V complex bind to immobilized rFVIIa. (A,B) Mock-transfected CHO cells (CHO-wt, 10⁶ cells/mL; A) and CHO cells transfected with the GPIb-IX-V complex (CHO-Ib, 10⁶ cells/mL; B) were allowed to adhere under static conditions to immobilized rFVIIa (10 μg/mL) for 60 minutes at 37°C. After gentle washing, adhesion was visualized by light transmission microscopy with a Zeiss 10×/0.22 numeric aperture lens on a Leica Diavert microscope (Leica, Wetzlar, Germany). Images were acquired using a JAI-CCD camera (Copenhagen, Denmark) coupled to a matrox frame grabber (Matrox Electronic Systems, Quebec, QC) using OPTIMAS 6.2 software (Optimas, Seattle, WA); original magnification 400×. (C) CHO-wt and CHO-Ib (10⁶ cells/mL) were allowed to adhere under static conditions for 60 minutes at 37°C to immobilized rFVIIa (10 μg/mL) or recombinant soluble tissue factor (TF; 10 μg/mL). Subsequently, TF-immobilized wells were blocked with 2% BSA, before incubation with rFVIIa or vehicle (“TF/rFVIIa” and “TF,” respectively). Adhesion was quantified by measuring the intrinsic phosphatase activity, and optical density is depicted as arbitrary units of adhesion (AU). Images and graph are representative of at least 3 independent experiments performed in triplicate. Error bars represent SD. *P < .01 compared with blank.