Westphal, Maria S.

Neurons upregulate major histocompatibility complex class I (MHC I) during demyelination, enabling the presentation of self-antigens to cytotoxic CD8 + T cells. While this phenomenon is well described in multiple sclerosis lesions, its functional significance for disease progression remains poorly understood. Here, we test the hypothesis that neuronal MHC I expression promotes CD8 + T cell-mediated neurodegeneration in demyelinating disease. Using genetic and viral approaches to selectively ablate β ₂-microglobulin (β₂M) in neurons, we demonstrate that the loss of neuronal MHC I limits antigen presentation, attenuates the activation of neuron-antigen–specific CD8 + T cells, and reduces the recruitment of these cells to the demyelinated central nervous system (CNS). In myelin oligodendrocyte glycoprotein (MOG₃₅–₅₅)-induced experimental autoimmune encephalomyelitis, CD8 + T cell ablation during active disease limited neuronal injury and improved clinical recovery. Similarly, neuronal β ₂M ablation decreased clinical disease burden without affecting CNS T cell infiltration. Likewise, in the context of cuprizone intoxication, neuronal β ₂M deletion reduced peripheral activation and CNS recruitment of CD8 + T cells recognizing a neuron-restricted neoantigen. It protected neoantigen-expressing neurons from cognate CD8 + T cell-mediated cytotoxicity. Collectively, these findings identify neuronal MHC I–dependent antigen presentation as a driver of both the immune surveillance of neuronal antigens and neuronal injury during demyelination.

This study reveals a novel role for Treg-derived IL-6R in supporting epithelial repair. Despite preserved immune-suppressive capacity, deletion of IL-6R from Tregs impairs epithelial transcription and worsens injury in colitis. We demonstrate that human intestinal organoids preferentially respond to trans- over classic IL-6 signaling. These findings introduce a Treg-specific role in immune-epithelial cross talk relevant to mucosal healing and inflammatory bowel disease.

Multiple sclerosis is characterized by CNS infiltration of autoreactive immune cells that drive both acute inflammatory demyelination and chronic progressive axonal and neuronal injury. Expanding evidence implicates CD8 + antineural T cells in the neurodegeneration that underlies irreversible clinical progression in multiple sclerosis, yet therapies specifically targeting this cell population are limited. CD8 + T cells from patients with MS exhibit increased engagement of the pentose phosphate pathway. Pharmacologic inhibition of the pentose phosphate pathway reduced glycolysis, glucose uptake, NADPH production, ATP production, proliferation, and proinflammatory cytokine secretion in CD8 + T cells activated by ligation of CD3 and CD28. Pentose phosphate pathway inhibition also prevented CD8 + T cell–mediated antigen-specific neuronal injury in vitro and in both an adoptive transfer–based cuprizone model of demyelination and in mice with experimental autoimmune encephalomyelitis. Notably, transcriptional profiling of CNS-infiltrating CD8 + T cells in patients with MS indicated increased pentose phosphate pathway engagement, suggesting that this pathway is involved in CD8 + T cell–mediated injury of axons and neurons in the demyelinated CNS. Inhibiting the pentose phosphate pathway disrupts CD8 + T cell metabolic reprogramming and effector functions, suggesting that such inhibition may serve as a therapeutic strategy to prevent neurodegeneration in patients with progressive MS.