Isolation of alpha-1 fetoprotein.

A suitable method of the isolation of alpha-1 fetoprotein for the needs of enzyme immunoassay of this oncofetal antigen is described. By combining isoelectric focusing and "indirect" affinity chromatography the preparation of alpha-1 fetoprotein was obtained that was not contaminated with IgG, contrary to the isolation performed by means of "direct" affinity chromatography on a carrier with coupled anti-alpha-1 fetoprotein antibodies, or other immunochemical methods that usually yielded contaminated preparations. Neither disc electrophoresis in PAA gel, immunoelectrophoresis, double radial immunodiffusion, nor biological experiments revealed any traces of ballast proteins in the resulting preparation; it seems suitable both for the preparation of monovalent antisera of a sufficient avidity, and as a standard for enzyme immunoassay.