Overview of Interferons

In studying the phenomenon of viral interference, Isaacs and Lindenmann discovered interferon in 1957. On the basis of this criteria the IFNs were initially classified into two types—the type I family composed of the acid-stable forms IFNα and IFNβ, whereas the acid-labile form, IFNγ, was classified as the lone type II IFN.2 In recent years, a third type of IFN has been described, IFNλ. Originally termed interleukin (IL)-28a/b and IL-29 these proteins have been re-classified as IFNs based on the similar modes of induction and anti-viral activities they share with the type I and type II IFNs. However, although the type I and type III IFNs are induced during a viral infection and are, at least in part，involved in host defense against viruses, the type II IFN is primarily involved in the allergic response, in host defense against intracellular pathogens and in control of tumors.

Ligand types	Names	Receptor chain 1	Receptor chain 2
Type I IFN	IFN-αIFN-βIFN-εIFN-κ IFN-ω IFN-υ	IFN-αR1(Also IFN-αRα, IFNAR1)	IFN-αR2(Also IFN-αRβ,IFNAR2)
Type II IFN	IFN-γ	IFN-γR1(Also IFN-γRα, IFNGR1)	IFN-γR2(Also IFN-γRβ,IFNGR2)
Type III IFN	IL-28AIL-28BIL-29	IL-28R1	IL-10R2