Effect of preshearing vWF. The mean velocity (A) and the total number (B) of rolling LβIXV cells were determined at a wall shear stress of 10 dyn/cm². In preshear experiments, before cells were introduced into the chamber, vWF immobilized on the glass coverslip was exposed to a shear stress of 40 dyn/cm² for 5 minutes by perfusing Dulbecco’s PBS through the chamber. Values are the mean ± SEM, n = 4 to 7.