Isolation of human complement component C3 from small volumes of plasma

A method for the isolation of 8-10 mg of human C3 from 20 ml of plasma is described. The procedure is simple and rapid with excellent yields in hemolytic activity (74%) and antigenic activity (68.7%). It consists of polyethylene glycol precipitation, DEAE-Sephacel chromatography, and immunoadsorption. The final product is free of contaminating proteins as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The simplicity and speed of this procedure allow for the continual availability of hemolytically active C3.