Resolution of human fibroblast interferon into two distinct classes by thiol exchange chromatography

Chromatography of crude and purified human fibroblast interferon on activated thiol Sepharose 4B yielded two classes of material exhibiting different stability to inactivation by mechanical stress. Interferon which bound to the gel accounted for 20--30 per cent of recoverable activity, could be eluted with reducing agents and was unstable. Unbound material did not bind on subsequent rechromatography and was stable to shear forces. Leucocyte interferon did not bind, nor did fibroblast interferon treated with thiol blocking reagents. Peak eluted fractions had a specific activity of up to 10(7.9) units per milligram of protein, representing a 1700 fold purification.