Interferon production by individual cells

A feline interferon production and assay system has been defined which allows measurement of the interferon produced by a single cell. It was found that 2–3 induced cells were required to reduce by 0.5 log¹⁰ the yield of vesicular stomatitis virus (VSV) from approximately 2500 target cells. The antiviral effect was characterized as interferon by several criteria. The presence of trypsin or pretreatment of the induced cells with actinomycin D eliminated the effect. The antiviral effect was species specific, and cell-free supernatants from target cell monolayers which had been exposed to induced cells could be used to protect other target cell monolayers. It was found that one interferon-producing cell provided significant (p < 0.05) 0.1 log₁₀ reduction of VSV yield from 2500 target cells. Analysis of the data obtained when 2 or 3 induced cells were used to provide antiviral protection indicated that approximately $\text{1}\text{3}$ of the cell population failed to respond measurably to the inducer. The number of cells required to protect target cells was found to be inversely proportional to the amount of interferon produced in monolayer culture.