Interferon lambda-1 (IFNL1) binds Interleukin-10 receptor subunit beta (IL10RB), which is associated with Non-receptor tyrosine-protein kinase TYK2 (TYK2), and Interferon lambda receptor-1 (IFNLR1), which is associated with Tyrosine-protein kinase JAK1 (JAK1). Interferon lambda-2 (IFNL2, IL28A), Interleukin-28B (IL28B, Interferon lambda-3) and Interferon lambda-1 (IFNL1, Interleukin-29) are related cytokines, collectively known as the type III interferons. They are distantly related to the type I interferons (IFNs) and are members of the class II cytokine family, which includes type I, II, and III interferons and the Interleukin-10 family (IL10, Interleukin-19 (IL19), Interleukin-20 (IL20), Interleukin-22 (IL22), Interleukin-24 (IL24), and Interleukin-26 (IL26)). They are encoded by genes that form a cluster on 19q13. Expression of all three IFNLs can be induced by viral infection. They share a heterodimeric class II cytokine receptor that consists of IFNLR1 and interleukin-10 receptor beta (IL10RB) (Kotenko et al. 2003, Sheppard et al. 2003). IL10RB is also part of the receptor complexes for IL10, IL22, IL24 and IL26. IFNL1, IFNL2 and IFNL3, like type I IFNs, can signal through ISRE regulatory sites and are likely to provide antiviral activity by the induction of at least a subset of IFN-stimulated genes (Dumoutier et al. 2004, Gad et al 2004, Sheppard et al. 2003).