Fig. 5.

Recovery of P4 cell induction and antitumor activity in aged mice by xenogeneic cell injection. (A) Schematic diagram of the experimental schedule. (B–D) Young (3–4 mo old) and aged (16–18 mo old) PD-1 KO mice were i.v. injected with Daudi cells (day −10). Ten days after injection (day 0), PLN cells of the mice were analyzed by FACS and real-time PCR. (B) Percentages of P1–P4 subsets relative to all CD8⁺ T cells in PLNs. (C) Expression levels of 1C-metabolism–related genes in CD8⁺ T cells. (D) CD45RB expression levels in P1 cells from PLNs. (E–I) Young (3–4 mo old) and aged (17–18 mo old) PD-1 KO mice were i.v. injected with or without (Ctrl) Daudi cells (day −10). Ten days after the transfer (day 0), the mice were i.d. inoculated with MC38 (E–G) or MC38-OVA (H and I) cells and used for the following experiments. MC38-tumor sizes (E) and percent survival (F). (G) The percentage of p-ZAP-70⁺ cells relative to all CD8⁺ T cells from DLNs on day 6. (H and I) Frequency of OVA tetramer⁺ CD8⁺ T cells in DLNs (H) or tumor tissues (I) on day 6. Data are presented as the mean ± SEM (n = 9–10 for B; n = 4–6 for C–I). *P < 0.05; **P < 0.01 (one-way ANOVA followed by Tukey’s test, log-rank test, or two-tailed unpaired Student’s t test).