Normal plasma contains VWF-cleaving activity.

The ULVWF strings with adherent platelets formed when washed platelets (A), but not platelet-rich plasma (B), were perfused over histamine-stimulated HUVECs. The ULVWF strings with adherent platelets that formed by perfusing washed platelets (C; arrow) were cleaved when normal platelet-poor plasma was perfused subsequently (D; arrow). The figure is representative of 28 separate experiments. Original magnifications × 400.