The impact of the type 2B mutant A1, Ile546Val, on PT-VWD platelet attachment and tether bond formation in flow. (A) Platelets (5 × 107/mL) purified from 2 patients with PT-VWD or 2 healthy individuals on 3 consecutive days were infused at the indicated wall shear rates through a parallel platelet flow for 5 minutes. The total number of platelets that attached to surface-immobilized recombinant type 2B mutant protein (100 μg/mL) was determined and compared (mean ± SD; n = 6). (B) Frequency of tether bonds formed between beads coated with a low density of type 2B mutant VWF-A1 and healthy or PT-VWD platelet substrates as a function of wall shear rate (s-1). (C) Representative graph depicting the distribution of interaction times for more than 35 individual transient attachment events that occurred between microspheres coated with WT or type 2B VWF-A1 and surface-immobilized platelets purified from healthy individuals or patient A with PT-VWD. Dissociation rate constants were estimated at wall shear stress of 1.0 dyne cm-2. koff is the negative slope of the linear regression through the experimental data.
