The Interferon-Lambda Family Celebrates 20 Years of Scientific Discovery.

It has now been 20 years since the original discovery of the interferon λ (IFN-λ) family (Kotenko et al., 2003; Sheppard et al., 2003) and 10 years since the subsequent discovery of IFN-λ4 (Prokunina-Olsson et al., 2013). The IFN-λ family (type III IFNs) includes 4 members: IFN-λ1, 2, 3, and 4, and all 4 of these proteins signal through the same heterodimeric receptor complex: IFN-λR1 plus IL-10R2. Throughout the past 20 years, much has been learned about the IFN-λ family and the important role of these cytokines in antiviral responses against viruses such as hepatitis C virus, influenza A virus, and SARS-CoV-2. This special issue of the Journal of Interferon & Cytokine Research (JICR) features a group of new reports that highlight recent developments regarding various aspects of IFN-λ-mediated responses. Many of these reports were first presented during the Interferon Lambda 2022 Satellite Meeting after the "Cytokines 2022" meeting in Hawaii. These articles underscore the fact that our understanding of the IFN-λ family continues to evolve and remains a critical subject area for additional future research.