FIG. 6.

Tregs inhibit IL-13 production by CD4⁺ T cells and protect against IAV. Two-day-old scurfy or heterozygous littermate control mice were infected i.n. with an LD₁₀ dose of the PR8 strain of IAV or left uninfected. Flow cytometry was used to determine the number of CD4⁺ Foxp3⁺ T cells in the lung digest (A) and the proportion of CD4⁺ T cells expressing IFNγ (B, C) or IL-13 (D) in the lungs over time. Insets (C, D) show representative histograms of IFNγ or IL-13 expression on CD4⁺ lung digest cells of scurfy (solid line), littermate controls (dotted line), and an isotype control (shaded histogram). Lung viral burden was determined by plaque assay on MDCK cells (E). Data represent the mean ± SD of 3–9 mice per group and are representative of three experiments. *p < 0.05 for infected scurfy compared to infected heterozygous littermate control, ^#p < 0.05 compared to all other groups, ^‡p < 0.05 compared to naive littermates.