FIG 2.

IRF9 deficiency impairs accumulation of effector CD8⁺ T cells and induces exhaustion. (A to F) WT, Irf9^−/−, and Ifnar^−/− mice were infected with LCMV-Arm i.p., and the spleens were analyzed at day 8 p.i. (A) Frequencies of CD8⁺ T cells and LCMV GP_33–41 and LCMV NP_396–404 dextramer-positive (Dex⁺) CD8⁺ T cells in WT, Irf9^−/−, and Ifnar^−/− mice. Left panels depict GP_33–41 Dex⁺ CD8⁺ T cells in naive (uninfected) mice. (B and C) Mean fluorescence intensities (MFI) for CD44 and KLRG1 of LCMV-GP_33–41 Dex⁺ CD8⁺ T cells in WT, Irf9^−/−, and Ifnar^−/− mice. (D) Splenocytes were stimulated with GP_33–41 peptide and analyzed for IFN-γ and TNF-α production by intracellular staining. n.c., nonstimulated control. The numbers display percentages of positive cells. (E and F) MFI for PD1 and LAG3 of LCMV-GP_33–41 Dex⁺ CD8⁺ T cells in WT, Irf9^−/−, and Ifnar^−/− mice. For all panels, representative histograms are shown, and bar diagrams display means and SEM (n = 5 per group). Data from one of two independent experiments with consistent results are shown. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; n.s., not significant (unpaired two-tailed Student's t test).