Monoclonal antibodies to human C4. I. Purification of hemolytically active C4 from small volumes of normal serum.

A C4-specific monoclonal antibody has been developed that allows the rapid purification of C4 from whole serum or plasma by affinity chromatography. 1- to 2-ml volumes of serum are loaded onto a small column of antibody-coupled agarose beads and washed through with buffer. C4 is eluted by adjusting the pH to 11.2. The purified C4 is free of extraneous proteins as detected by SDS-polyacrylamide gel electrophoresis and retains high activity as assessed by hemolytic assay and incorporation of [14C]-methylamine. Columns are reusable, and the entire procedure can be adapted for large-scale purifications.