Anti–ADAMTS-13 antibodies detected in an ADAMTS-13 antigen-specific ELISA system. NHP was used as a control. The error bars of the NHP indicate the 2 times added SD calculated from several plasma lots. Plasma dilutions ranging from 1:20 to 1:1200 were analyzed. (A) Anti–ADAMTS-13 IgG titer. (B) Anti–ADAMTS-13 IgM titer.