Interferons

The term interferon (IFN) was first used by Isaacs and Lindenmann in 1957 to describe substances secreted by chicken chorioallantoic membranes exposed to influenza virus. The soluble interferon secreted into the culture medium rendered other membrane cultures resistant to virus challenge. This effect was termed virus “interference,” and served as the origin of the name interferon. More than 60 years later it is clear that interferons are members of the large cytokine family of evolutionarily conserved pleiotropic regulators of cellular function. Mammalian IFN are broadly classified into Type I, Type II, and Type III. Type I IFN include alpha (IFNA), beta (IFNB), delta (IFND), epsilon (IFNE), tau (IFNT), and omega (IFNW). The Type II IFN class is represented by a single member, termed IFN gamma (IFNG), and the Type III IFN class contains at least three members that are known either as IFN lambda (IFNL) 1, 2, and 3 or as interleukin (IL) 29, 28A, and 28B. The roles of IFN are perhaps best described as components of the innate arm of the immune system and serve as early responders to invading pathogens. Interferons play a key role in reducing pathogen replication, and regulating immune responses to infection. However, a subclass of Type I IFN is now known to serve as vital controllers of early signaling between the developing embryo (conceptus) and the uterine endometrium in ruminant ungulates. It is this role of interferons that will be reviewed here.