Binding of VM16d to GPIbα chimeras.

Specific binding of ¹²⁵I-labeled anti-GPIbα monoclonal antibody, VM16d (1 μg/mL), to CHO βIX cells (5 × 10⁶/mL) co-expressing wild-type human GPIbα, or canine–human chimeras of GPIbα for 30 minutes at 22°C. Binding is expressed relative to specific binding of ¹²⁵I-labeled WM23 for each cell line, to account for any differences in expression of GPIbα between different populations of cells. Specific binding for each antibody was calculated by subtracting nonspecific binding measured in the presence of 100 μg/mL unlabeled antibody in a parallel assay. Error bars, ± SEM (n = 2).