Neutrophils sustain effective CD8 T-cell responses in the respiratory tract following influenza infection

Neutrophils have an important role in early host protection during influenza A virus infection. Their ability to modulate the virus‐specific adaptive immune response is less clear. Here, we have used a mouse model to examine the impact of neutrophils on CD8+ T‐cell responses during influenza virus infection. CD8+ T‐cell priming, expansion, migration, cytokine secretion and cytotoxic capacity were investigated in the virus‐infected airways and secondary lymphoid organs. To do this, we utilised a Ly6G‐specific monoclonal antibody (mAb; 1A8) that specifically depletes neutrophils in vivo. Neutrophil depletion early after infection with influenza virus strain HKx31 (H3N2) did not alter influenza virus‐derived antigen presentation or naïve CD8+ T‐cell expansion in the secondary lymphoid organs. Trafficking of virus‐specific CD8+ T cells into the infected pulmonary airways was also unaltered. Instead, early neutropenia reduced both the overall magnitude of influenza virus‐specific CD8+ T cells, together with impaired cytokine production and cytotoxic effector function. Therefore, neutrophils are important participants in anti‐viral mechanisms that sustain effective CD8+ T‐cell responses in the respiratory tract of influenza virus‐infected mice.