PURPOSE: Adoptive T cell immunotherapy (ACT) has emerged as a viable therapeutic for peripheral and central nervous system (CNS) tumors. In peripheral cancers, optimal efficacy of ACT is reliant on dendritic cells (DCs) in the tumor microenvironment. However, the CNS is largely devoid of resident migratory DCs to function as antigen-presenting cells during immunotherapy. Herein, we demonstrate that cellular interactions between adoptively-transferred tumor-reactive T cells and bone marrow-derived HSPCs lead to the generation of potent intratumoral DCs within the CNS compartment. EXPERIMENTAL DESIGN: We evaluated HSPC differentiation during ACT in vivo in glioma-bearing hosts and HSPC proliferation and differentiation in vitro using a T cell co-culture system. We utilized FACS, ELISAs, and gene expression profiling to study the phenotype and function of HSPC-derived cells ex vivo and in vivo. To demonstrate the impact of HSPC differentiation and function on anti-tumor efficacy, we performed survival experiments. RESULTS: Transfer of HSPCs with concomitant ACT led to the production of activated CD86+CD11c+MHCII+ cells consistent with DC phenotype and function within the brain tumor microenvironment. These intratumoral DCs largely supplanted abundant host myeloid-derived suppressor cells. We determined that during ACT, HSPC-derived cells in gliomas rely on T cell-released IFN-gamma to differentiate into DCs, activate T cells, and reject intracranial tumors. CONCLUSIONS: Our data supports the use of HSPCs as a novel cellular therapy. While DC vaccines induce robust immune responses in the periphery, our data demonstrates that HSPC transfer uniquely generates intratumoral DCs that potentiate T cell responses and promote glioma rejection in situ.