Isolation of factor h from fraction i paste

A method for preparing an enriched Factor H composition from plasma, the method comprising the steps:

• (A) precipitating Factor H from a Cohn plasma pool, in a first precipitation step, the first precipitation step performed at a final concentration of from 6% to 10% alcohol at a pH of from 7.0 to 7.5, thereby forming a first precipitate and a first supernatant;
• (B) extracting the Factor H from the first precipitate with a first Factor H extraction buffer, thereby preparing an extracted Factor H composition;
• (C) admixing polyethylene glycol (PEG) into an extracted Factor H composition, in a second precipitation step, the second precipitation step performed at a final concentration of from 2% to 7% PEG at a pH of from 7.0 to 9.0, thereby forming a second precipitate and a second supernatant;
• (D) admixing PEG into the second supernatant, in a third precipitation step, the third precipitation step performed at a final concentration of from 10% to 20% PEG at a pH of from 7.0 to 9.0, thereby forming a third precipitate and a third supernatant;
• and
• (E) extracting the Factor H from the third precipitate with a second Factor H extraction buffer, thereby forming an enriched Factor H composition.