Immunoblot of anti–ADAMTS13 IgG and VWF multimeric pattern. (A) Immunoblot showing the presence of IgG reacting with recombinant (r) ADAMTS13. Serum samples were reacted with human rADAMTS13 previously transblotted to a nitrocellulose membrane. The presence of IgG was detected by a peroxidase conjugate goat anti–human IgG antibody. Lane 1: patient serum collected during an acute phase; lane 2: patient serum collected at remission before plasma (day –23); lane 3: patient serum collected at day 0 before rituximab treatment; lane 4: patient serum at day 123; and lane 5: serum from a healthy subject. The time of sampling is indicated by the upward-pointing filled arrowhead in Figure 1B. In samples containing an inhibitor, a reactive band of about 170 kDa corresponding to rADAMTS13 was found (arrow). (B) Representative images of VWF multimers in patient and control plasma. The origin of the gel is on the top; the arrow indicates the position of UL VWF multimers. Lane 1: control plasma pool; lane 2: patient sample collected before plasma at day –23; lane 3: patient sample collected before rituximab infusion (day 0); and lane 4: patient sample collected at day 88. The time of sampling is indicated by the vertical double-headed arrow in Figure 1B.