Fig. 1

PD-1 expression on T cells was upregulated during glioma progression that correlate with apoptosis. a–d Flow cytometry analysis of PD-1 expression on glioma-infiltrating T cells at indicated time points. Representative data of the PD-1 expression of CD4⁺ T cells (a) and CD8⁺ T cells (c) at the indicated time point and the statistical summary for CD4⁺ T cells (b) and CD8⁺ T cells (d), n = 3–4. N, normal brain; 10, 10 days after tumor inoculation; 20, 20 days after tumor inoculation; TM, terminal stage. e–h Flow cytometry analysis of T cell apoptosis by annexin V. Representative data of the apoptosis level of CD4⁺ T cells (e) and CD8⁺ T cells (g) from the peripheral blood and glioma tissue. The statistical summary for CD4⁺ T cells (f) and CD8⁺ T cells (h), n = 12. i Representative staining for Iba1 (green) and CD8 (red) in tumor-bearing brain (day 20). Arrow, morphologically intact T cells; asterisk, disintegrated T cells. Scale bar, 20 μm. One-way ANOVA was performed in b and d. Unpaired Student’s t test was performed in f and h. *p < 0.05; **p < 0.01. All values are shown as mean ± SEM