Fig. 6.

IRF4 supports survival of CD8⁺ tissue-resident memory T cells. (A) Representative gating strategy for CD45IV⁻ CD69⁺ CD8⁺ T_RM cells in lung. (B) Irf4^+/+ mice were infected with LmOVA. After 5 wk, tissues were analyzed for CD8⁺ T cells with a T_RM phenotype. Mean fluorescence intensity of IRF4 staining of CD45IV⁻ CD44⁺ CD62L⁻ CD69⁻ CD8⁺ T effector/effector memory (T_Eff/EM) cells, of CD45IV⁻ CD44⁺ CD62L⁻ CD69⁺ CD8⁺ T_RM cells and corresponding CD45IV⁺ CD8⁺ T_Eff/EM cells in blood, and of CD44⁻ CD62L⁺ naïve CD8⁺ T cells. Representative result of two independent experiments, each with three individually analyzed mice. Mean ± SEM, paired t test. (C) Irf4^+/+, Irf4^+/−, and Irf4^−/− mice were infected with LmOVA. After 5 wk, tissues were analyzed. Frequencies of CD8⁺ T cells with a T_RM-cell phenotype among CD45IV⁻ CD8⁺ T cells. Pooled results from two independent experiments with five or six mice/group. Mean ± SEM, ANOVA, and Bonferroni’s post-test. (D) Rag1^−/− mice were reconstituted with T cells from naïve Irf4^fl/+×CreER^T2 and Irf4^fl/−×CreER^T2 mice. Recipient mice were infected with LmOVA. After 5 wk, mice were treated with tamoxifen for 5 d. After 6 mo, tissues were analyzed for CD8⁺ T cells with a T_RM phenotype among CD45IV⁻ CD8⁺ T cells. Pooled results from two independent experiments with five and six mice. Mean ± SEM, paired t test. *P ≤ 0.05, **P ≤ 0.01.