Studies on the enhancement of interferon production in human diploid (FS-4) cells by ultraviolet

Interferon production stimulated with Polyinosinate-Polycytidylate [Poly (I). Poly (C)] in cultures of human FS-4 cells was enhanced ('superinduced') by the irradiation of cells with UV at the time of induction. UV showed no additional enhancing action on interferon production in cultures already superinduced by the sequential treatment with cycloheximide and actinomycin D; UV doses above 1,000 erg/mm2 inhibited interferon synthesis. In UV-irradiated cells interferon production remained sensitive to inhibition by high concentrations of actinomycin D for at least 3 hr after exposure to Poly (I). Poly (C). Irradiation of induced cells at 4, 5 or 6 hr after stimulation with Poly (I). Poly (C) prevented the rapid decline (shutoff) of interferon synthesis seen in control cultures. All these results support the conclusion that the action of UV protects the interferon mRNA from inactivation. This effect, and the fact that interferon mRNA synthesis can occur after the irradiation of cells with superinducing doses of UV, form the basis of the enhancement of interferon production by UV.