Editing Interferon (section)

{{short description|Signaling proteins released by host cells in response to the presence of pathogens}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
{{Redirect|IFN}}
{{Infobox protein family
| Symbol = Interferons
| Name = Interferon 
| image = 1RH2 Recombinant Human Interferon-Alpha 2b-01.png
| width =
| caption = The molecular structure of human interferon-alpha ({{PDB|1RH2}})
| Pfam= PF00143
| InterPro= IPR000471
| SMART= SM00076
| Prosite = PDOC00225
| SCOP = 1au1
| CATH = 1au0
| TCDB =
| OPM family=
| OPM protein=
|CDD=cd00095
}}
{{Infobox protein family
|Name=Interferon type II (γ)
|InterPro=IPR002069
|Pfam=PF00714
|Symbol=IFN-gamma
|CATH=1d9cA00
|SCOP=d1d9ca_
|image=Image:1HIG Interferon-Gamma01.png
|caption=The three-dimensional structure of human [[interferon gamma]] ({{PDB|1HIG}})
}}
{{Infobox protein family
|Name=Interferon type III (λ)
|Pfam=PF15177
|Symbol=IL28A
|InterPro=IPR029177
|CATH=3og6A00
}}

'''Interferons''' ('''IFN'''s, {{IPAc-en|ˌ|ɪ|n|t|ər|ˈ|f|ɪər|ɒ|n}} {{respell|IN|tər|FEER|on}}<ref>{{Cite web | url=https://www.lexico.com/en/definition/interferon | title=Interferon {{pipe}} Definition of Interferon by Lexico | access-date=2019-10-17 | archive-date=2020-12-22 | archive-url=https://web.archive.org/web/20201222183022/https://www.lexico.com/en/definition/interferon | url-status=live }}</ref>) are a group of [[signaling protein]]s<ref>{{cite journal | vauthors = De Andrea M, Ravera R, Gioia D, Gariglio M, Landolfo S | title = The interferon system: an overview | journal = European Journal of Paediatric Neurology | volume = 6 | issue = 6 Suppl A | pages = A41–6; discussion A55–8 | date = 2002 | pmid = 12365360 | doi = 10.1053/ejpn.2002.0573 | s2cid = 4523675 }}</ref> made and released by [[host cells]] in response to the presence of several  [[virus]]es. In a typical scenario, a virus-infected cell will release interferons causing nearby [[cell (biology)|cells]] to heighten their anti-viral defenses.

IFNs belong to the large class of [[proteins]] known as [[cytokine]]s, molecules used for communication between cells to trigger the protective defenses of the [[immune system]] that help eradicate pathogens.<ref name="Cohen and Parkin">{{cite journal | vauthors = Parkin J, Cohen B | title = An overview of the immune system | journal = Lancet | volume = 357 | issue = 9270 | pages = 1777–1789 | date = June 2001 | pmid = 11403834 | doi = 10.1016/S0140-6736(00)04904-7 | s2cid = 165986 }}</ref> Interferons are named for  their ability to "interfere" with [[viral replication]]<ref name="Cohen and Parkin" /> by protecting cells from [[virus infection]]s. However, virus-encoded genetic elements have the ability to antagonize the IFN response, contributing to viral pathogenesis and viral diseases.<ref>{{cite journal | vauthors = Elrefaey AM, Hollinghurst P, Reitmayer CM, Alphey L, Maringer K | title = Innate Immune Antagonism of Mosquito-Borne Flaviviruses in Humans and Mosquitoes | journal = Viruses | volume = 13 | issue = 11 | pages = 2116 | date = October 2021 | pmid = 34834923 | pmc = 8624719 | doi = 10.3390/v13112116 | doi-access = free }}</ref> IFNs also have various other functions: they activate [[immune cells]], such as [[natural killer cell]]s and [[macrophage]]s, and they increase host defenses by up-regulating [[antigen presentation]] by virtue of increasing the expression of [[major histocompatibility complex]] (MHC) [[antigens]].  Certain symptoms of infections, such as [[fever]], [[muscle pain]] and "flu-like symptoms", are also caused by the production of IFNs and other [[cytokines]].

More than twenty distinct IFN genes and proteins have been identified in animals, including humans. They are typically divided among three classes: Type I IFN, Type II IFN, and Type III IFN.  IFNs belonging to all three classes are important for fighting [[viral infections]] and for the regulation of the immune system.