In the GL261 murine GBM model, combination immunotherapy with anti-CXCR4 and anti-PD-1 significantly reduced CD11b+ macrophage and monocytic MDSC infiltration while lowering the proportion of CD4+FoxP3+ Treg cells, thereby enhancing CD8+ tumor-infiltrating lymphocyte (TIL) cytotoxicity. Here, CXCR4 is linked to glioblastoma.