Interferon production: variation in yields from human cell lines

Interferons Alpha, Beta, and Omega

Interferon alpha (IFN-α) is a mixture of closely related proteins, termed “subtypes,” expressed from distinct chromosomal genes. Interferon β (IFN-β) is a single protein species and is molecularly related to IFN-α subtypes, although it is antigenically distinct from them. IFN omega (IFN-ω) is antigenically distinct from IFN-α and IFN-β but is molecularly related to both. The genes of three IFN subtypes are tandemly arranged on the short arm of chromosome 9. They are transiently expressed following induction by various exogenous stimuli, including viruses. They are synthesized from their respective mRNAs for relatively short periods following gene activation and are secreted to act, via specific cell surface receptors, on other cells. IFN-α subtypes are secreted proteins and as such are transcribed from mRNAs as precursor proteins, pre-IFN-α, containing N-terminal signal polypeptides of 23 hydrophobic amino acids (aa) mainly. Pre-IFN-β contains 187 aa, of which 21 comprise the N-terminal signal polypeptide and 166 comprise the mature IFN-β protein. IFN-ω contains 195 aa—the N-terminal 23 comprising the signal sequence and the remaining 172, the mature IFN-ω protein. At the C-terminus, the aa sequence of IFN-ω is six residues longer than that of IFN-α or IFN-β proteins. IFN-α, as a mixture of subtypes, and IFN-ω may be produced together following viral infection of null lymphocytes or monocytes/macrophages. The biological activities of IFNs are mostly dependent upon protein synthesis with selective subsets of proteins mediating individual activities. IFNs can also stimulate indirect antiviral and antitumor mechanisms, depending upon cellular differentiation and the induction of cytotoxic activity.

Depressed interferon synthesis in skin fibroblasts from lung cancer patients

Skin fibroblast cell cultures, derived from male adult lung cancer patients, an adult control population, and a newborn population were examined for their susceptibility to transformation with Kirsten murine sarcoma virus and their ability to respond to an interferon inducer (poly I.poly C). An association between sensitivity to viral transformation and induction of interferon was observed. Cultures derived from lung cancer patients demonstrated an increased sensitivity to virus transformation and a decreased ability to respond to interferon induction as compared with age-matched controls and newborns.

Human trophoblast interferon: pattern of response to priming and superinduction of purified term trophoblast and choriocarcinoma cells

We recently described a beta interferon response of primary cultures of term human trophoblast exposed to poly(I:C). The response pattern has now been studied further with priming and superinduction both of normal placental cell types and JAR, JEG-3 and BeWo choriocarcinoma cells. Pre-treating placental trophoblast cells, fibroblasts and macrophages with human interferon generally led to increased yields of interferon after poly(I:C) induction, whereas choriocarcinoma cells did not respond to priming. All the cells showed the superinduction phenomenon although to varying degrees. The combination of priming and superinduction conditions led to the production of very high yields of interferon in placental fibroblast cultures. The combined procedure also produced more interferon in macrophage cultures than priming or superinduction alone. Combined superinduction and priming of normal trophoblast did not produce higher yields than those obtainable by superinduction alone. These data might help to provide additional insight into the cellular control mechanisms of sensitivity of normal and malignantly transformed cells to interferon. Furthermore, the large quantity of trophoblast interferon produced by superinduction could be used for studies of its anti-viral and immunomodulatory effects.

Depressed interferon synthesis in skin fibroblasts from lung cancer patients

Skin fibroblast cell cultures, derived from male adult lung cancer patients, an adult control population, and a newborn population were examined for their susceptibility to transformation with Kirsten murine sarcoma virus and their ability to respond to an interferon inducer (poly I X poly C). An association between sensitivity to viral transformation and induction of interferon was observed. Cultures derived from lung cancer patients demonstrated an increased sensitivity to virus transformation and a decreased ability to respond to interferon induction as compared with age-matched controls and newborns.

Production of human alpha- and beta- interferons by human-rodent hybrids

Attempts were made to demonstrate human alpha interferon production in virally induced human-rodent cell hybrids. In all hybrids investigated human beta-interferon production was detected when the relevant human chromosomes were retained, but only low levels of human alpha interferon could ever be detected even when human chromosome 9, which contains at least eight alpha-interferon genes, was present in the hybrid. The detection of human alpha interferon was made possible only by the use of specific antisera to human alpha and beta interferon and the sensitive virus yield-inhibition assay. Evidence is presented for independent regulatory mechanisms governing the expression of human alpha and beta interferons in human-rodent hybrids.

Production of interferon in human diploid cells at different population doubling levels

Interferon (IFN) yield after superinduction declined gradually by in vitro senescence of the cells, while it remained unchanged in IFN-pretreated cells. IFN yield after stimulation with Newcastle disease virus remained unchanged by in vitro senescence.