Figure 2.

Expression of IL15Rα in brain tumor tissue of murine models of GBM. (A) The diagram shows the experimental set up used for generation of Gr1+ cells for downstream analysis of IL15Rα expression. (B) RNAseq analysis of Gr1⁺ cells harvested from the brain and spleens (paired samples) of mice bearing established CT2A tumors Gr1⁺ cells were harvested from 10 mice in three independent experiments, n=3. Paired t-test. *p<0.05. (C) RT-qPCR analysis of IL15Rα mRNA expression in Gr1⁺ cells harvested from the brains and spleens of mice bearing CT2A and GL261, n=8. Paired t-test. *p<0.05. (D) Flow cytometry analysis of IL15Rα expression on the surface of total population of myeloid cells (CD45⁺ CD11b⁺ cells) and different subsets of myeloid cells, as well monocytic MDSCs (CD11c^-CD11B⁺ Ly6G^- Ly6C⁺), polymorphonuclear MDSCs (CD11c^-CD11B⁺ Ly6G⁺ Ly6C^-), TAMs (CD45⁺ CD11B⁺ F4/80^hi Ly6C^-), B cells (CD45⁺ CD19⁺), and dendritic cells (CD45⁺ CD11b^low CD11c^hi) harvested from brains and splenocytes of mice bearing intracranial CT2A and GL261 murine glioma tumors, n=4. Paired t-test. ***p<0.001. (E) CD8+T cells proliferate in the presence of recombinant murine IL15 in coculture with wild type MDSC, but not with IL15Rα KO MDSCs or absence of IL15 (negative control). A representative flow plot showing proliferation of Cell Trace Violet labeled CD8+T cells at 1:32 ratio of MDSCs to T cells (red) or negative control (blue; unstimulated). Quantitative analysis of T cells proliferation in cocultures are shown. CD8+T cells activated with activating beads served as a positive control in the proliferation assay. GBM, glioblastoma; KO, knock-out; MDSCs, myeloid-derived suppressor cell.