Immunoadsorbent affinity purification of the fifth component (C5) of human complement and development of a highly sensitive hemolytic assay.

The fifth component of complement (C5) has been isolated from human serum in fully hemolytically active form by immunoadsorbent and anion exchange column chromatography. The immunoadsorbent column was prepared by the covalent coupling of the purified IgG fraction obtained from monospecific goat anti-human C5 antiserum to CNBr activated Sepharose 4B. Establishment of appropriate conditions for the dissociation and elution of functionally active C5 from the immunoadsorbent column was of central importance in the development of this purification procedure. The C5 preparations exhibited final yields of 20--50% with 570--710-fold purification factors based on recovery of specific hemolytic activity. These preparations were free of contaminating serum proteins as judged by SDS-polyacrylamide slab gel electrophoretic and immunochemical criteria. A C5-depleted reagent (C5D) was generated from the non-adsorbed protein containing fractions obtained subsequent to the passage of freshly drawn NHS plus 10 mM EDTA through the monospecific anti-C5 Sepharose 4B column. Upon reconstitution of C5D with Ca2+, Mg2+, and C1q, this reagent was utilized for the detection and quantitation of C5 hemolytic activity. The purified C5 preparations contained 1.5--2.5 x 10(12) effective molecules/mg protein and NHS expressed 0.5--2.0 x 10(11) effective molecules/ml.