Epitope mapping of anti-ADAMTS-13 autoantibodies in patients with acquired TTP. The culture media of various COOH-terminally truncated mutants were blotted onto polyvinylidene diflouride membranes. The membranes were reacted with anti-FLAG M2 MoAb as a positive control (A) or anti–ADAMTS-13 inhibitory autoantibodies from 3 patients with acquired TTP (B-D).