Bystander activation through interleukin 1 signaling is necessary and sufficient for the induction of T cell responses during live viral infection, reports a paper published online in Nature Immunology. These results suggest interleukin 1 could be potentially used as a vaccine adjuvant.
Vaccine-induced immune responses require direct recognition of molecular patterns associated with the pathogen - which are part of the vaccine formula - by professional antigen-presenting cells called dendritic cells (DCs). DC-intrinsic signaling through specific receptors that can recognize such pathogen-specific signatures is required to induce T cell responses against the virus, while inflammatory cytokines are not sufficient to induce DC activation during vaccination. Akiko Iwasaki and colleagues show that during infection with live influenza virus, signaling through the cytokine interleukin 1 in DC is both required and sufficient to promote the expansion of virus-specific T cells. The authors conclude that this bystander activation may be important during physiologic live virus infection, as DCs may be killed or incapacitated by the virus.