Graduate Student Geisel Sch. of Med. at Dartmouth Lebanon, New Hampshire, United States
Introduction/Rationale: Resident memory T cells (TRM) reside in diverse tissues, including the central nervous system (CNS), where they provide rapid, site-specific immune responses upon secondary challenge. Mouse models have demonstrated the importance of CNS TRM in protection against neurotropic pathogens, involvement in neurological disorders, and maintenance of CNS homeostasis. However, understanding of human brain TRM has been limited by challenges in acquiring timely and adequate tissue samples.
Methods: We developed a unique pipeline combining on-site autopsies with rapid tissue dissociation to collect specimens from multiple CNS regions, including the cerebellum, hippocampus, frontal cortex, and meninges. Flow cytometry was used to quantify CD8+ TRM marked by canonical residency markers CD69+ CD103+. Single-cell RNA sequencing profiled TRM transcriptional signatures across regions. Additionally, barcoded tetramers identified virus-specific T cells, and TCR sequencing characterized clonal relationships between different regions.
Results: High frequencies of CD8+ TRM marked by CD69+ CD103+ were detected in all CNS tissues. Single-cell RNA sequencing revealed location-specific TRM signatures; meningeal T cells clustered distinctly, enriched for Granzyme B and Interferon-gamma, while hippocampus, cortex, and cerebellum TRM expressed TOX and HOBIT. Live tissue sampling from epilepsy surgeries showed analogous TRM signatures. Tetramer analysis identified influenza-, SARS-CoV-2-, Epstein-Barr virus (EBV)-, and cytomegalovirus (CMV)-specific T cells distributed throughout the brain. TCR sequencing demonstrated clonal overlap of virus-specific TRM clones across CNS regions, indicating an antigen-driven expansion that supports a durable, heterologous antiviral TRM repertoire in the brain.
Conclusion: These findings reveal regional heterogeneity and specialization of human brain TRM, underscoring their roles in neurological diseases and the need to understand their biology to develop targeted immunotherapies.
