Upshaw-Schulman syndrome-associated ADAMTS13 variants possess proteolytic activity at the surface of endothelial cells and in simulated circulation. oleh Anton Letzer, Katja Lehmann, Christian Mess, Gesa König, Tobias Obser, Sven Peine, Sonja Schneppenheim, Ulrich Budde, Stefan W Schneider, Reinhard Schneppenheim, Maria A Brehm