Effects of RAM.1 on GPIb-dependent adhesion to bovine and human VWF under flow conditions.

K562-GPIb/V/IX cells (A), CHO-GPIb/IX cells (B), or human platelets (C) were perfused through microcapillaries coated with 25 μg/mL bovine VWF (BVWF, upper panels) or human VWF (HVWF, lower panels). Cells (1 × 10⁶/mL) or platelets (4 × 10⁸/mL) resuspended in Tyrode buffer were preincubated for 10 minutes with 10 μg/mL RAM.1 (■) or control rat IgG1 (▪) and perfused at a shear rate of 150 s^-1 for 10 minutes. The number of adherent cells per field was counted off-line at the indicated times. (♦) indicates adhesion to albumin-coated control microcapillaries. The rate and extent of adhesion of transfected cells or platelets was decreased by RAM.1 treatment and this effect was more pronounced on human VWF (approximately 90%-100% inhibition) than on bovine VWF (50% inhibition). Results are expressed as the means ± SEM of 4 separate experiments performed in duplicate.