Streptococcal preparation OK-432-induced interferon in human leukocytes: purification and characterization

Interferon production was induced in leukocyte suspensions from human buffy coats after stimulation with the streptococcal preparation OK-432. At day 2-3 the induced interferon reached a maximal level of 0.9 units/1,000 cells. By a combination of batch adsorption/elution on silicic acid, batch adsorption to DEAE-Sephacel, affinity chromatography on concanavalin A-Sepharose and on poly(U)-Sepharose, this interferon could be purified to a specific activity of 10(7.5) units/mg protein. The antiviral activity was characterized as being solely due to gamma-type interferon by a variety of physicochemical, biochemical and serological criteria. Its molecular weight as determined by gel filtration amounted to 53,000 daltons, and its activity was completely neutralized by highly specific antisera to human gamma-type interferon (45K). The OK-432-induced interferon, as the crude supernatant of stimulated leukocytes, and at several stages of its purification, was found to stimulate the natural killer cell activity of fresh human lymphocytes.