(A) Proportions of cells expressing T cell and activation markers in the SCseq data set (4 mice pooled per group). (B) Flow cytometric analysis of the B16F10-OVA tumor-infiltrating immune cells on day 12 showing elevated levels of CD8⁺ T cells in tumors of WT mice, and higher levels of IFN-γ production by these cells. Two-tailed t test was used for statistical comparisons. *P ≤ 0.05; ns, P > 0.05. (C) Expression levels of T cell activation markers and effector genes within the CD3⁺CD8⁺ cells are shown. Sell, Pdcd1, and Tnfrsf9 encode CD62L, PD-1, and 4-1BB respectively. In these plots, each dot represents a single cell. Normalized expression values were used, and random noise was added to show the distribution of data points. The box plots show interquartile range and the median value (bold horizontal bar). Average expression value per sample is indicated by the red points. Wilcoxon’s test was used for statistical comparisons. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001; ns, P > 0.05. (D) Gene set enrichment analysis (GSEA) of CD3⁺CD8⁺ cells in SCseq data on day 12. Normalized enrichment score (NES) and adjusted P value are shown. WT CD8⁺ T cells were enriched for cell cycle genes and genes upregulated in effector CD8⁺ T cells (gene sets were derived from MSigDB) (33). (E) Analysis of activation markers within activated CD8⁺ T cell cluster (as defined in Figure 1) showing a more robust activation phenotype in WT T cells. (F) Analysis of the miR-155 target gene expression in activated CD8⁺ T cell clusters on day 9. The x axis of the stacked histograms indicates the normalized expression values of target genes and the y axis indicates the scaled frequency of cells. To account for differences in cell numbers per sample, the frequency of cells with no expression of the indicated genes was scaled to 1. Dashed lines indicate the average expression values in each group. (G) Analysis of miR-155 targets in activated CD8⁺ T cell clusters on day 12. Data were scaled similarly to panel F.