Binding of anti-ADAMTS13 IgGs from TTP patients to ADAMTS13 and variants. WT or variants M1 to M5 (50 ng) were incubated with mAb II-1 (35μM) or TTP patient plasmas (5-10 μL each, depending on plasma IgG concentrations). The immune complexes were pulled down with protein A-Sepharose 4B and detected by Western blotting with anti-V5. Anti-V5 IgG coupled Sepharose 4B beads were used for a positive control. Normal IgG from healthy persons (nIgG) was used for a negative control.