Factors influencing the production of interferon from L cells.

The production of interferon from Newcastle disease virus-infected mouse L929 cells was investigated in relation to superinduction procedures, cell density, cellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and rate of incorporation of 14C-labeled protein hydrolysate into trichloroacetic acid-precipitable material. Densely populated cultures did not have their interferon production enhanced through "superinduction" using cycloheximide, actinomycin D, or the two antimetabolites in combination. These dense cultures produced more interferon per cell than less dense cultures, even though the interferon production from the latter cells could be enhanced two- to threefold by cycloheximide or combined cycloheximide and actinomycin D. Cells in densely populated cultures relative to those from sparsely populated cultures were smaller in volume, had a correspondingly reduced protein content and a lower concentration of cAMP, and were less able to concentrate 14C-labeled protein hydrolysate, although proportionally they were just as efficient in incorporating labeled precursors into trichloroacetic acid-precipitable polypeptides.