Figure 3: IL-10 interacts with CD8⁺ T cell immunity during tumorigenesis and inhibits DC cell maturation to facilitate tumor growth.

(A) The blockade of Nrp-1 in melanoma tumor-bearing mice up-regulated CD8a expression in tumor tissues and decreased CD8a protein expression in IL10KO tumor-bearing mice. Representative immunohistochemistry images were obtained using a microscope with a 20X objective. Statistical analysis of the mean IOD for tumor cell proliferation was performed with by Image-Pro Plus software. Nonlinear regressions were performed using GraphPad Prism (San Diego, CA, USA). (B) Neutralization of Nrp-1 in IL10^−/− or WT mice implanted with B16/F10 tumors augmented CD8a⁺IFN-γ⁺ T cells in the tumor microenvironment compared with the control based on flow cytometry staining. (C) Tumor tissues were harvested from tumor-bearing mice on day +15. The tumor-derived cytokine Granzyme B was measured using the mouse multiplexed bead-based immunoassay, MilliplexMapKit (Luminex kit MCD8MAG-48K, Millipore Corporation). (D)Mouse spleen-derived DC (spDC) activation and maturation status were detected by flow cytometry. Significantly more mature CD11b⁺CD11c^hi cells (mDC, left) were observed in IL10-knockout tumor-bearing mice compared with WT; however, no significant differences were detected in immature CD11b^hi CD11c^hi (imDC, middle) and CD11b⁺CD11c^int-low cells (MDSC, right). Panels (A–D) The mean ± SEM is shown, n = 3–4 mice. *P < 0.05, **P < 0.01, ***P < 0.001, one-way ANOVA.