[Purification of the ninth component of human complement (C9)].

A large amount of human C9 was purified from plasma by the following procedures: 1) Polyethylene glycol precipitation; 2) Depletion of plasminogen by passing over an L-lys-sepharose column; 3) DEAE-sephadex A-50 chromatography; and 4) Hydroxylapatite (HA) chromatography. The method of C9 purification was improved by altering the column-elution conditions and by the establishment of a novel method for preparing high-flow-rate HA. As a result, the rate of recovery of C9 was high (28.2%) and no impurities were detected either on gel electrophoretic or immunochemical examination. The hemolytic activity of purified C9 was retained.