Separation of functionally or highly pure C2 from human plasma with Sepharose and a lectin of Euonymus europeus

A method is described for isolating both functionally and highly pure C2 from normal human serum or plasma. Functionally pure C2 was obtained by a two-step method of ammonium sulfate (AS) fractionation of plasma or serum and chromatography on AH-Sepharose containing a bound lectin of Euonymus europeus. The functionally pure C2 can be isolated in 2 days, and is used routinely as a reagent for functional hemolytic titrations of C3 and C4 in the Clinical Immunology Laboratory. Highly pure C2 was isolated by the two-step fractionation with AS followed by chromatography on CM-cellulose, aged CNBr-activated Sepharose 4B, and AH-Sepharose-lectin. The major difficulty for isolating highly pure C2 was its separation from Factor B of the alternative complement pathway. The yield of C2 varied from 30 to 40 per cent. Following electrophoresis and staining on polyacrylamide gels, the single band was hemolytically active C2.