IFNAR1 and influenza: Moreover, while the IFN signature was completely abolished in influenza infected IFNAR1−/−IL-28Rα−/− cells, the addition of neutralizing antibodies against secreted type I and type III IFNs, used in combination on wild-type epithelia or for the complementary IFN on IFN receptor single knock-out epithelia, had little effect on ISG induction (not shown), indicating that even minute concentrations of IFN were still able to induce ISG expression in responsive cells.