IL-28 and IL-29: Newcomers to the interferon family

IL-28 and IL-29 were recently described as members of a new cytokine family that shares with type I interferon (IFN) the same Jak/Stat signalling pathway driving expression of a common set of genes. Accordingly, they have been named IFNλ. IFNsλ exhibit several common features with type I IFNs: antiviral activity, antiproliferative activity and in vivo antitumour activity. Importantly, however, IFNsλ bind to a distinct membrane receptor, composed of IFNLR1 and IL10R2. This specific receptor usage suggests that this cytokine family does not merely replicate the type I IFN system and justifies its designation as type III IFN by the nomenclature committee of the International Society of Interferon and Cytokine Research.