Rat fibroblast-derived interferon: production in serum-free medium and enhancement by theophylline.

Incubation of rat fibroblasts (RFA-1) with theophylline after Newcastle disease virus (NDV) induction, increased rat fibroblast interferon (RfIFN) yields 3 to 10-fold. However, incubation with butyric acid for 24 or 48 h before NDV addition resulted in no change or decrease in IFN production. Combined treatment with butyric acid and theophylline did not improve the yields obtained with the methylxanthine alone. Production of IFN by RFA-1 cells was the same in serum-free and in serum-containing media. These findings will facilitate RfIFN production and purification.