Tumor Immunogenicity Shapes CNS Immune Niches and CD8⁺ T Cell Fate in Glioblastoma

Immunotherapeutic strategies have largely failed in glioblastoma (GBM), in part because the spatial and temporal choreography of anti-tumor immunity across central nervous system (CNS) compartments remains poorly defined. Here, using longitudinal, compartment-resolved profiling of the deep cervical lymph nodes (dcLNs), cranial meninges, and tumor tissue in two preclinical GBM models of differing immunogenicity, we delineate how tumor immunogenicity shapes CNS immune engagement. Although early immune priming occurred in both models, as evidenced by similar temporal patterns of dcLN activation, they diverged markedly at the CNS border. In the highly immunogenic setting, the meninges underwent profound remodeling, assembling dense CD3⁺/B220⁺ lymphoid aggregates indicative of robust local immune activation. By tracking T cell responses to an endogenous retroviral antigen expressed by both tumors, we detected antigen-specific CD8⁺ T cells in the meninges as well as the tumor bed, demonstrating that the meningeal compartment actively contributes to anti-GBM immunity rather than serving as a passive inflammatory site. CD8⁺ T cell differentiation trajectories varied substantially with anatomical context and tumor immunogenicity. During intermediate tumor progression, meningeal CD8⁺ T cells were enriched for PD-1⁺TCF1⁺Tim-3⁻ stem-like and, later, CD44⁺CD62L⁺ central-memory phenotypes, whereas tumor-infiltrating counterparts rapidly acquired cytotoxic programs, yielding PD-1⁺GzmB⁺ and TNF⁺ effectors. Although the full spectrum of CD8⁺ T cell states was present in both immunogenicity contexts, their distribution differed: highly immunogenic tumors maintained robust stem-like and memory reservoirs in the meninges, correlating with sustained polyfunctionality and delayed exhaustion intratumorally. In contrast, poorly immunogenic tumors showed diminished meningeal reservoirs and were dominated in the tumor bed by hyperactivated PD-1⁺GzmB⁻ populations prone to early terminal dysfunction. These findings support a model in which the meninges serve as a regenerative immune niche that sustains durable cytotoxic responses.Tumor immunogenicity also reshaped the myeloid landscape: highly immunogenic tumors induced macrophages and microglia co-expressing activation and regulatory programs, whereas their counterparts in poorly immunogenic tumors remained largely inert. Collectively, our work defines a spatiotemporal model in which tumor immunogenicity is a key architect of immune topology across CNS compartments, positioning the meninges as a critical site sustaining long-lived anti-tumor immunity.