Binding of the anti–GP Ib monoclonal antibody WM23 and vWf to GP Ib chimeras.
(A) Relative binding of WM23 to CHO βIX cells (5 × 106/mL) or CHO βIX cells expressing wild-type canine GP Ibα, human GP Ibα, or canine–human chimeras of GP Ibα, as indicated by mean fluorescence intensity in flow cytometric analysis (see “Materials and Methods”). Data were normalized to CHO βIX cells expressing wild-type human GP Ibα. (B) Specific binding of 125I-labeled vWf (1 μg/mL) to the cells described in the legend to panel A in the presence of botrocetin (2.5 μg/mL final concentration) for 30 minutes at 22°C. Nonspecific binding was determined in the absence of modulator. (C) Binding of vWf to the cells described in the legend to panel A, but in the presence of ristocetin (1 mg/mL final concentration) instead of botrocetin. (D) Relative vWf binding in the presence of ristocetin (C) compared with botrocetin (B). Data in A-C are the means of triplicate determinations (± SEM) and are representative of 3 separate experiments with different populations of cells.
