ADAMTS13 and thrombotic thrombocytopenic purpura: Two types of anti-ADAMTS-13 antibodies have been described: one inhibiting (neutralizing) ADAMTS-13 proteolytic activity17,18 and the other binding to the protease and accelerating its clearance from plasma through opsonization and/or other yet unresolved mechanisms.69 Both of these antibodies may be simultaneously present in many TTP patients.65