Figure 1. PD-1–laIL-2 selectively targets intratumoral CD8⁺ T cells.

(A) BALB/c mice (n = 5/group) were inoculated with 2 × 10⁶ A20 tumor cells and were treated with 50 μg anti–PD-1 and/or 200 μg anti–IL-2Rβ on day 14. Tumor growth was assessed twice a week. (B) IL-2Rα expression on CD8⁺, CD4⁺, and Treg cells in peripheral blood, spleen, and tumor samples (indicated as PB, SP, and tumor in the figures) from A20 tumor-bearing mice (n = 5/group). (C) Percentages of PD-1⁺ T cells in peripheral blood, spleen, and tumor samples from A20 tumor-bearing mice (n = 5/group). (D) Mean fluorescence intensity (MFI) of PD-1 on Treg and CD8⁺ T cells in the spleen and on Treg and PD-1⁺CD8⁺ T cells in the tumors from A20 tumor-bearing mice (n = 5/group). (E) Schematic diagram of the anti–PD-1 × laIL-2 heterodimer (PD-1–laIL-2). (F and G) PD-1–wtIL-2 and PD-1–laIL-2 bind to Treg (F), CD8⁺, and CD4⁺ (G) T cells in the spleen of A20 tumor-bearing mice (n = 5/group). (H) Erb–laIL-2 and PD-1–laIL-2 bind to PD-1⁺CD8⁺ T cells in tumors from A20 tumor-bearing mice (n = 5/group). (I) PD-1–laIL-2 binds to CD8⁺ T cells in the spleen and to PD-1⁺CD8⁺ T cells in tumors from A20 tumor-bearing mice (n = 5/group). (J) PD-1–laIL-2 binds to PD-1^–CD8⁺ and PD-1⁺CD8⁺ T cells in tumors from A20 tumor-bearing mice (n = 5/group). Data represent mean ± SEM from 2 to 3 independent experiments. The P value was determined by 2-way ANOVA with Geisser-Greenhouse’s correction (A), 1-way ANOVA with Tukey’s multiple comparisons test (D and H), 2-way ANOVA with Tukey’s multiple comparisons test (G and I), or 2-tailed unpaired t test (J). The normality of the data was confirmed by the Shapiro-Wilk test. ***P < 0.001, ****P < 0.0001.