Fig. 4: CD8 is indispensable in blocking CD73 to enhance RT-mediated systematic immune responses and abscopal effects.

1 × 106 MC38 cells were injected into the left flank of C57BL/6 mice three days after the first injection (1 × 106) into the right flank. For CT26 model, we utilized 2 × 105 CT26 cells injecting into BALB/c mice. The pictures of primary and secondary tumors of C57BL/6 (A) and BALB/c mice (C), and their tumor growth curves of each treatment group (B, D) are shown. E, F In CD8 + T cells depletion experiment, the first anti-CD8 antibodies were administered three days prior to RT, with subsequent applications twice weekly throughout the course of treatment. Tumor growth curves of each treatment group (E), with corresponding survival data (F), are shown. G, H Splenic CD8 + T cells were isolated using magnetic bead isolation (Miltenyi Biotec) and pre-activated with Dynabeads mouse CD3/CD28 beads (IBA Life Sciences) for 48 h. After 48 h of pre-activation, they were co-cultured with MC38 cells treated ± 8 Gy RT, ±CD73i for 48 h, followed by flow analysis 24 h later. G Quantification of IFN-γ+, TNF-α+, and GrzmB+ cells as a proportion of CD8+ cells. H Quantification of PD-1+ and TIM3+ cells as a proportion of CD8+ cells. Statistical variations were analyzed utilizing the One-way ANOVA (B, D, E, G, H) or Kaplan–Meier method with the log-rank test (F). Data are expressed as mean ± SEM (n = 10 per group).*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.