Purification of mouse interferon by sequential affinity chromatography on poly(U)--and antibody--agarose columns

Mouse interferon has been purified to homogeneity by twostep affinity chromatography. Two polypeptide bands were obtained on sodium dodecyl sulphate--polyacrylamide gel electrophoresis migrating at molecular weights 35,000 and 22,000, both having antiviral activity. The 35,000 but not the 22,000 band, also stained with periodic acid--Schiff. The specific activity was 8 X 10(9) of our laboratory units, corresponding to 2.4 X 10(9) NIH reference units.