A modification of an affinity procedure for purification of human C1- inhibitor that provides a homogeneous stable preparation

Human C1- inhibitor can be rapidly purified by the affinity chromatography procedure described by Pilatte and his associates (1989), but the inhibitor so purified breaks down during storage or is in a cleaved form when initially purified. By adding an ion-exchange chromatography procedure after the affinity chromatography, a stable, single species of C1- inhibitor molecules is obtained. It is likely that serine proteinases in trace amounts, which may be complexed with some of the C1- inhibitor, are removed during the ion-exchange procedure. This procedure provides a highly purified and useful preparation of C1- inhibitor.