Figure 3. The presence or absence of brain tumor-derived IDO contextually regulates T cell infiltration and long-term survival in T cell -competent, but not -deficient mice.

Wild-type (WT) mice were intracranially-injected (ic.) 4×10⁵ GL261 cells transduced with -scrambled shRNA (vector control, V_c; white bars) or -shRNA specific to IDO (IDO knockdown, IDO_kd; black bars). Naïve (control; grey bars) mice were used as a baseline of normal T cell levels in the brain. The (A) frequency and (B) absolute numbers of total CD4⁺ T cells, CD8⁺ T cells and CD4⁺FoxP3⁺ regulatory T cells isolated from the brain of tumor-bearing mice were analyzed from naïve, or at 1, 2 and 3 weeks post-injection. All T cell populations were initially identified by the expression of CD3. Bar graphs in figures A – B are shown as mean ± SEM and are representative of two independent experiments (n = 4 – 5 mice/group). Kaplan-Meier survival curves for (C) WT, CD4-deficient (CD4^−/−; lack CD4⁺ T cells), CD8-deficient (CD8^−/−; lack CD8⁺ T cells) and recombinase activating gene 1-deficient (Rag1^−/−; lack all functional T or B cells) mice ic. 4×10⁵ V_c or IDO_kd GL261 cells. Mouse survival was analyzed for up to 150 days (n = 7 – 16 mice/group) and reflects the pooled data resulting from 2 – 3 independent experiments. *p < 0.05; **p < 0.01; ***p < 0.001.