The mechanism of interferon production

Interferons are formed when most cells are treated with viruses or double-stranded RNA (to form IFN-$\alpha$ or $\beta$, or both) or when lymphoid cells are treated with mitogens or the appropriate antigen (to form IFN-$\gamma$). Interferon-$\alpha$ and $\beta$ are formed as a result of transcription of cellular genes - probably in response to double-stranded RNA in the cytoplasm. The process can be controlled at three levels. (1) In mouse terato-carcinoma stem cells or early mouse embryos the interferon system is inaccessible and only becomes inducible as differentiation proceeds. (2) The target(s) responding to double-stranded RNA probably involve sequences upstream from the 5' end of the interferon genes, sequences now becoming accessible by gene cloning. (3) Levels of interferon mRNA can be regulated either by an increased rate of transcription or by an increased half-life of the mRNA.