Affinity chromatography of the inhibitor of the vWF-cleaving protease on protein A-Sepharose and protein G-Sepharose. Two milliliters of patient plasma (PP) obtained on day 221 was applied onto a column of either protein A-Sepharose or protein G-Sepharose (4 mL bed volume each). Protease activity was assayed in mixtures of NHP (4 vol) and peak fractions eluted from the chromatographic columns (1 vol). A, B, C, D, and E refer to the chromatographic fractions eluted; TBS, Tris-buffered saline.