Nasal anti-CD3 modulates T cell and Microglia activation in aged mice 2267372

Abstract Introduction Cellular senescence is characterized by a permanent arrest of the cell cycle, often accompanied by dysfunctional regulatory T cell (Treg) activity and loss of homeostatic microglia, contributing to neurotoxicity. We previously demonstrated that intranasal administration of anti-CD3 (αCD3) induces several Treg subpopulations that produce anti-inflammatory cytokines such as TGF-β and IL-10, which can reduce microglial inflammation and ameliorate neurodegenerative conditions like multiple sclerosis (MS) and Alzheimer’s disease (AD). Methods In this study, we treated aged female mice with intranasal αCD3 and evaluated the effects on brain immune cell populations and behavior. Mice aged 8, 16, and 70 weeks received 1 μg of nasal αCD3 three times per week for three months. Following treatment, we assessed motor function, memory, anxiety, and depression-like behavior. Brain cell suspensions were sorted into three CD45-defined populations for single-cell enriched analysis, and spleens were analyzed by flow cytometry. Results While no significant differences were observed in behavioral outcomes, single-cell analysis revealed that αCD3 treatment altered the myeloid compartment. We found increased clustering of dendritic cells, oligodendrocytes, macrophages, and monocytes in treated mice compared to controls. Additionally, we detected an upregulation of T cell markers such as CD39 and TIGIT, and reduced expression of proinflammatory cytokines including IL-17, TNF-α, and IFN-γ. Conclusion Collectively, our findings suggest that nasal αCD3 induces a systemic anti-inflammatory immune response and modulates microglial-related pathways, which may confer neuroprotective benefits in the context of aging. Funding Source The ALS Association, NIH-National Institutes of Health Topic Categories Neuroimmunology (NEUR)