Interferon lambda-2, also known as Interleukin 28A, is an antiviral cytokine with immunomodulatory activity and is distantly related to the IL-10 family and type I interferons. IL28A along with IL29 and IL28B, are three closely related cytokines that form a cytokine gene cluster that use a distinct receptor system which induces antiviral defence signals. IL28A interacts with a heterodimeric class II cytokine receptor ligand and leads to the activation of the JAK/STAT signalling pathway, which ultimately leads to IFN-stimulated gene (ISG) and MHC class I antigen expression. It also plays a key role in antiviral defence in Toll-like receptors (TLR) and intestinal epithelia.