Figure 1. Short-course ATRi plus RT promotes tumor antigen–specific CD8⁺ T cell expansion in the DLN.

(A–E) CT26 tumor–bearing mice were treated with ATRi on days 1–3 (ATRi QDx3), RT on days 1–2 (RT 2 Gy x 2), ATRi QDx3 + RT, or vehicle, and tumor-draining lymph nodes (DLNs) were immunoprofiled at day 9. (A) Representative cytograms depicting CD62L and CD44 expression on CD8⁺ T cells. Activated and naive CD8⁺ T cell subsets were defined as effector/effector memory (Tem; CD44^hiCD62L^lo), central memory (Tcm; CD62L^hiCD44^hi), or naive (Tn; CD62L^hiCD44^lo). (B) Quantitation of CD8⁺ Tem cells as percentages of CD8⁺ T cells or per 1,000 cells stained. Data from at least 4 independent experiments with 1–3 mice per group. n = 9 Vehicle, 7 ATRi QDx3, 9 RT, 11 ATRi QDx3 + RT. (C–E) Tumor antigen–specific CD8⁺ T cells were labeled with AH1 Pentamer. (C) Representative cytograms depicting Pentamer⁺ CD8⁺ T cells. Fluorescence-minus-one (no Pentamer) and naive (negative, no tumor) controls shown. (D) Quantitation of Pentamer⁺ CD8⁺ T cells as percentages of CD8⁺CD4^– cells or CD45⁺ immune cells. (E) Quantitation of Pentamer⁺ CD8⁺ Tem and Tcm cells as percentages of CD8⁺CD4^– Tem and Tcm cells. (D and E) Data from at least 5 independent experiments with 1–5 mice per group. n = 12 Vehicle, 13 ATRi QDx3, 13 RT, 14 ATRi QDx3 + RT. (B, D, and E) Mean and SD bars shown. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 by ANOVA with Tukey’s multiple-comparison test.