IFNL1 and Down syndrome: Following infection of airway epithelial cells by respiratory viruses, such as influenza virus, rhinovirus, parainfluenza virus type 1, respiratory syncytial virus (RSV), or severe acute respiratory syndrome (SARS) coronavirus, several proinflammatory cytokines are induced, including interleukin-1β (IL-1β), IL-6, IL-8, and interferon lambda 1 to 3 (IFN-λs) (28, –, 35).