Purification of two subspecies of human gamma (immune) interferon.

Abstract

Interferon (IFN)-.gamma. was produced in cultures of human leukocytes by combined stimulation with 12-O-tetradecanoylphorbol 13-acetate and phytohemagglutinin. IFN-.gamma. was purified by sequential adsorption and elution from controlled-pore glass and concanavalin A-Sepharose and by subsequent adsorptive removal of contaminating proteins on DEAE-Sephacel at pH 8.0. Treatment of such partially purified IFN-.gamma. preparations with the anionic detergent sodium dodecyl sulfate (NaDodSO4) (0.1% at 20-25.degree. C) decreased biological activity to .apprx. 5-20%. When analyzed by NaDodSO4/polyacrylamide gel electrophoresis the bulk of IFN activity not destroyed by NaDodSO4 treatment was recovered from 2 peaks with apparent MW of 20,000 and 25,000. The 2 activity peaks showed close correspondence with Coomassie blue-stained bands regularly demonstrable in purified supernatants from induced cultures but absent from culture supernatants from uninduced cells. The 2 bands, isolated in pure form, apparently represent subspecies of IFN-.gamma.. Native IFN-.gamma. had a lower affinity for alkyl agarose columns than human IFN-.alpha. or IFN-.beta. did, suggesting that IFN-.gamma. is a relatively hydrophilic protein. Sulfhydryl-specific binding of native IFN-.gamma. to an Affi-Gel 501 column suggested that this IFN contains free SH.