Purification of factor XII (Hageman factor) from human plasma

Factor XII was purified from human plasma in four steps, in the presence of a contact activation inhibitor, hexadimethrine bromide, and soy bean trypsin inhibitor (SBTI), an inhibitor of plasma proteases, which act on factor XII. After adsorption with aluminum hydroxide (1 : 10), the plasma was precipitated with polyethylene glycol. The protein precipitating between 4.0 and 16% saturation was redissolved in about 30% of the starting plasma volume and chromatographed. The first chromatographic step was anion exchange chromatography on QAESephadex, in the presence of hexadimethrine bromide and SBTI. The SBTI was used also during the first half of chromatography on CM-Sephadex, from which factor XII eluted in the second half. As a fourth preparative step factor XII was subjected to either gel filtration on Sephadex G-100 or affinity chromatography. The latter consisted of an immunoadsorbent column, the antibody being against contaminating proteins isolated from factor XII-deficient plasma. The final product exhibited a sharp intense band by SDS-disc gel electrophoresis, with an estimated molecular weight of 78,000. The method is suitable for the purification of factor XII, which is a trace protein, from large volumes of plasma.