ISGs are induced in the absence of detectable type I and III IFNs.

Wild-type, MAVS^−/− and IRF3^−/−IRF7^−/− MTEC were either mock infected or infected with PR8 and their RNA analyzed 24 hpi for the induction of (A) both IFNs (IL-28A/B and IFNβ) and (B) ISGs (Oasl2, Ifi203, Rsad2). All the transcripts were first normalized to HPRT levels and then expressed as fold induction relative to the mean of mock infected controls, +/− SEM. (C) Viral replication was measured by qRT-PCR on the Influenza A Matrix gene and expressed as copy number +/− SEM.