IL-1R signaling in dendritic cells replaces pattern recognition receptors to promote CD8(+) T cell responses to influenza A virus

Immune responses to vaccines require direct recognition of pathogen-associated molecular patterns (PAMPs) through pattern recognition receptors (PRRs) on dendritic cells (DCs). Unlike vaccines, infection by a live pathogen often impairs DC function and inflicts additional damage to the host. Here, we found that following live influenza A infection, signaling through the interleukin-1 receptor (IL-1R), but not the PRRs, TLR7 and RIG-I, is required for productive CD8(+) T cell priming. DCs activated by IL-1 in trans were both required and sufficient for the generation of virus-specific CD8(+) T cell immunity. Our data reveal a critical role of a bystander cytokine in CD8(+) T cell priming during a live viral infection.