To define the major cell subsets that contribute to the therapeutic effects of αPD + αGITR therapy, we adoptively transferred Treg cells, CD8 T cells, or both Treg cells and CD8 T cells into Rag1–/– hosts, followed by orthotopic implantation of GL261-MGH or CT2A GBM tumors. Here, RAG1 is linked to glioblastoma.