IFNL1 and viral infectious disease: To directly address the importance of endogenous IFNλ1 and IFNλ2/3 in controlling viral infection we infected T84 WT, IFNλ1 KO, and IFNλ2/3 KO cells with VSV-GFP, RV-UnaG, MRV, and VV-GFP.