[Characteristics of the factors that suppress and stimulate interferon production]

A repressor of interferon production is contained in the hyaloplasm of the chick embryo fibroblast cells in the state of hyporeactivity. A factor stimulating interferon production (FSIP) was found in the hyaloplasm of the cells subjected to single or double induction with poly (pI) x poly (pC) followed by exposure to actinomycin D. Both preparations were of the protein nature and possessed high biological activity. They repressed or stimulatd interferon production at a dilution of 1:512-1:1024. The preparations had tissue and inductor specificity, did not affect the Venezuelan equine encephalomyelitis virus and interferon antiviral activity. Unlike the repressor, the FSIP proved to be thermolabile and pH-sensitive in acid media. The half lives of the repressor and stimulator were about 10 and 5 hours respectively.