Examination of parameters affecting human interferon production with microcarrier-grown fibroblast cells

Various parameters were examined for their effects on interferon production with human fibroblast cells (FS-4) grown on microcarriers, using a superinduction procedure. Optimal concentrations of cycloheximide and actinomycin D during induction were 10 micrograms/ml, respectively. Cells required 5 to 6 h of exposure to cycloheximide and at least 2 h of exposure to actinomycin D to achieve maximum yields. FS-4 cells were found to grow well at low serum concentrations (2.5 and 5%) and actually produced higher yields of interferon than cells grown at higher serum concentration (10 and 20%). Kinetics of interferon production at various temperatures revealed that significantly higher yields could be obtained at 34 degrees C than at either 37 or 30 degrees C. Priming cells for 16 h with 50 U of interferon per ml resulted in consistently higher yields of interferon. By modifying the superinduction procedure in accordance with the above findings, it is now possible to consistently obtain interferon yields of greater than 20,000 international units per 10(6) cells.