The monoclonal antibody 20A5 recognizes human ADAMTS-13, A Disintegrin And Metalloprotease with ThromboSpondin type 1 domain 13. ADAMTS-13 is produced by hepatic stellate cells and in smaller amounts by human endothelial cells, and is present in plasma at a concentration of approximately1 ug/ml.ADAMTS-13 is a zinc-containing metalloprotease belonging to the ADAMTS family characterized by a protease domain, an adjacent disintegrin-like domain, one or more thrombospondin type 1 repeats, a cystein-rich domain and a typical spacer region. ADAMTS-13 is composed of a series of domains (amino to carboxy terminal): metalloprotease, disintegrin-like, central thrombospondin-1 (TSP-1), cysteine-rich, spacer, seven additional TSP-1 domains and two unique CUB domains. ADAMTS-13 has no hydrophobic transmembrane domain, and hence it is not anchored in the cell membrane. The apparent molecular weight is 170 or 190 kDa on non-reducing or reducing SDS-PAGE, respectively.ADAMTS-13 has an important function in haemostasis, where it catalyzes the cleavage of the peptide bond between tyrosine-1605 and methionine-1606 in the A2 domain of von Willebrand Factor (VWF), resulting in 2 electrophoretic reduced fragments of 176 and 140 kDa, respectively. This process renders large multimers less adhesive and hence less reactive in the setting of thrombus formation. ADAMTS-13 is therefore said to be a natural anti-thrombotic agent.Severe ADAMTS-13 deficiency is associated with systemic microvascular thrombosis in familial or acquired thrombotic thrombocytopenic purpura (TTP). The accumulation of non-cleaved large VWF multimers causes spontaneous systemic platelet aggregation blocking oxygen supply to vital organs. This life-threatening disorder can lead to ischemic disease with (multiple) organ failure.The monoclonal antibody 20A5 recognizes the central to C-terminal TSP-1 repeats 2 to 5 of ADAMTS-13 (amino acid 686-894).