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Production of High-Titered Interferon in Cultures of Human Diploid Cells

The effect of incubation with interferon prior to the stimulation of interferon production (priming) and of sequential treatment with cycloheximide and actinomycin D (superinduction) on the interferon yield from polyinosinic-polycytidylic acid (poly I·poly C)-induced diploid human foreskin cell cultures (FS-3 strain) was studied. Suitable priming with interferon produced, on the average, about an eightfold increase over the control yield, with a greater increase noted on some occasions when the control interferon yield was very low. Under the optimal conditions carefully defined in our experiments, superinduction produced about a 100-fold increase over the average control yield, resulting in interferon yields of about 10,000 reference units from cultures containing about 106 cells. Combined superinduction and priming did not produce yields markedly higher than obtainable by superinduction alone. Essentially similar results were obtained in cultures of human embryonic kidney cells and in FS-3 cells stimulated with other double-stranded polynucleotide inducers. However, stimulation of cells with certain concentrations of a mixture of diethylaminoethyl-dextran and poly I·poly C altered the interferon response; the yield was considerably higher than in cells stimulated with poly I·poly C alone, but it could not be markedly increased further by superinduction.