Interferon type III

The type III interferon group is a group of anti-viral cytokines that in humans consists of a singular family, IFN-λ (lambda). Their function is similar to that of type I interferons, but is less intense and serves mostly as a first-line defense against viruses in the epithelium.

In humans, the IFN-λs are IFN-λ1, , IFN-λ3, and IFN-λ4. The first three used to be known as IL29, IL28A, and IL28B respectively. They were discovered in 2003.

IFN-λ2 and IFN-λ3 plays a role in immune defense against viruses, including the induction of an "antiviral state" by turning on Mx proteins, 2',5'-oligoadenylate synthetase as well as ISGF3G (Interferon Stimulated Gene Factor 3).