Schematic protein domain structure of ADAMTS13 and localization of anti-ADAMTS13 autoantibody epitopes. The ADAMTS13 protein consists of 1427 amino acid residues and the domain structure includes a signal peptide (S) and a pro-peptide (P), a metalloprotease, a disintegrin (Dis), a cysteine-rich (Cys), a spacer, and 2 CUB domains, as well as 8 thrombospondin type 1 repeats (1-8) (top row). Bottom rows (A-C): Lines below ADAMTS13 depict the ADAMTS13 fragments used for epitope mapping of anti-ADAMTS13 Abs. Y indicates that Abs directed against the respective ADAMTS13 fragment were found in a certain proportion of patients investigated (percentage indicated). In all 3 studies (A-C), only patients suffering from acute TTP with severe acquired ADAMTS13 deficiency were investigated. Row A: Klaus et al investigated 25 patients using E coli–derived recombinant ADAMTS13 fragments.¹⁷  Row B: Luken et al performed epitope mapping in 7 patients using full-length ADAMTS13 and ADAMTS13 fragments produced in insect cells.¹⁸  Row C: Zheng et al performed epitope mapping on 67 patient samples using rADAMTS13 and rADAMTS13 fragments produced in mammalian cell lines.¹⁹