Table 1.

Provides an overview of the different subtypes of IFN found in humans, key references and main characteristic is listed.

Type	Subtypes	Receptor	Comments	References
Type I IFNs
IFN‐α	IFN‐α1, ‐α2, ‐α4, ‐α5, ‐α6, ‐α7, ‐α8, ‐α10, ‐α13, ‐α14, ‐α16, ‐α17, ‐α21	IFN‐αR1/IFN‐αR2	IFN‐α is primarily produced by pDCs	Cella et al (1999), Barchet et al (2002), Dai et al (2004), Hardy et al (2004), Jaks et al (2007)
IFN‐β		IFN‐αR1/IFN‐αR2	IFN‐β is produced by most infected cells	Platanias (2005), Khaitov et al (2009), Ioannidis et al (2013)
IFN‐ε		IFN‐αR1/IFN‐αR2	IFN‐ε is associated with the female reproductive tract	Fung et al (2013), Marks et al (2019)
IFN‐κ		IFN‐αR1/IFN‐αR2	IFN‐κ is selectively expressed in keratinocytes	LaFleur et al (2001)
IFN‐ω		IFN‐αR1/IFN‐αR2	One of the least studied IFNs but the presence of neutralizing auto‐antibodies against it in severe COVID‐19 patients suggests its role in antiviral immunity may be underappreciated	Hauptmann and Swetly (1985), Bastard et al (2020)
Type II IFNs
IFN‐γ		IFN‐γR1/ IFN‐γR2	Not discussed here
Type III IFNs
IFN‐λ	IFN‐λ1, ‐λ2, ‐λ3, ‐λ4	IFN‐λR1/IL‐10R2	IFN‐λ is produced by infected cells at barrier tissues such as epithelial cells in the respiratory tract	Meager et al (2005), Sommereyns et al (2008), Jewell et al (2010), Mordstein et al (2010), Crotta et al (2013), Wack et al (2015), Ye et al (2019)