(A) Overview of the different mouse strains used for the experiments. The crossed arrows indicate deleted Hdac1 and Hdac2 alleles. (B) Histograms showing HDAC2 and HDAC1 expression levels in TCRβ⁺CD4⁺ splenocytes isolated from WT, HDAC1^cKO, HDAC2^cKO, HDAC1^HET-HDAC2^cKO, and HDAC1^cKO-HDAC2^HET mice. (C) Flow cytometry analyses showing CD4, IFN-γ, granzyme B (GzmB), and EOMES expression in WT, HDAC1^cKO, HDAC2^cKO, HDAC1^HET-HDAC2^cKO, and HDAC1^cKO-HDAC2^HET CD4⁺ T cells and WT CD8⁺ T cells activated with anti-CD3 and anti-CD28 for 3 days in the presence of IL-2. (D) Summary diagrams showing the percentages of IFN-γ⁺, granzyme B⁺, T-bet⁺, and EOMES⁺ cells of the indicated genotype as described in C and D. For CD8α⁺, WT MFI levels were set as 1, and relative MFI levels in HDAC1^cKO, HDAC2^cKO, HDAC1^HET-HDAC2^cKO, and HDAC1^cKO-HDAC2^HET CD4⁺ and WT CD8⁺ T cells are shown. Each symbol indicates 1 independent biological sample. Horizontal bars indicate the mean. *P < 0.05, **P < 0.01, and ***P < 0.001, 1-way ANOVA analysis followed by Tukey’s multiple-comparisons test (CD8⁺ WT is shown as control and was not included in the statistical analysis). (E) Histograms showing T-bet and CD8 expression in WT, HDAC1^cKO, HDAC2^cKO, HDAC1^HET-HDAC2^cKO, and HDAC1^cKO-HDAC2^HET CD4⁺ and WT CD8⁺ T cells activated as described in C. (B, C, and E) Numbers indicate the percentage of cells in the respective quadrants or gates or, as indicated, the MFI. (B and E) The dotted vertical lines indicate the peak of the WT histogram (for MFI), while the vertical solid line indicates the gating region for the percentage of cells. Data are representative (B, C, and E) or show a summary (D) of at least 7 (B) or 6 (C, D, and E) mice that were analyzed in at least 3 (B) or 4 (C, D, and E) independent experiments.