VWF and thrombotic thrombocytopenic purpura: The spacer domain is essential for proteolysis of full‐length vWF under flow conditions [29, 32, 33], and data in the present study also agree with the previous studies also found that 98% of HIV‐associated TTP patient samples had IgG autoantibodies that bind to both the cysteine‐rich as well as the spacer domains.