Figure 4.

Exogenous IL-33, but not endogenous IL-33, enhanced CD8 T-cell responses against influenza infection. (A–C) C57BL/6 mice were injected intranasally with 0.5 μg of rIL-33 or PBS daily for five days and infected with 50 PFU of PR8 influenza virus. (A) On day seven post-infection, the recruitment of CD3ε⁺ CD8⁺ T-cells to lungs was assessed by flow cytometry. (B) IFN-γ production by CD3ε⁺ CD8⁺ CD44^hi T-cells post-stimulation with NP_366–374 peptide was measured by intracellular staining. (C) NP_366-374 antigen-specific CD3ε⁺ CD8⁺ CD44⁺ T-cells were measured by pentamer staining. (D) IL-33^+/− and IL-33^−/− mice were infected with 50 PFU of PR8 influenza virus. On day seven post-infection, IFN-γ production by CD3ε⁺ CD8⁺ CD44^hi T-cells post-stimulation with NP_366-374 peptide was measured by intracellular staining. ** p < 0.01; ns, not significant.