Blood cytotoxic natural killer-like CD8 + CD94+ T cells migrate to the brain and predict multiple sclerosis severity

: Memory CD8+ T cells are central to multiple sclerosis (MS) and undergo clonal expansion, but disease-associated states remain incompletely defined. By single-cell profiling of circulating memory CD8+ T cells from patients with relapsing-remitting MS, healthy volunteers, and neuroinflammatory controls, we identified an MS-associated cytotoxic subset with NK-like features. These cells increase around relapse activity and belong to an oligoclonal reservoir. In an independent cohort sampled at the first clinical event, an elevated frequency of NK-like CD8+ T cells predicted an aggressive MS course two years later and was associated with a migratory/inflammatory program. Bulk and single-cell RNA-seq confirmed the NK-like transcriptional signature, and functional assays demonstrated TCR-independent cytotoxicity. Immunostaining and spatial transcriptomics revealed enrichment of these cells in MS lesions and a spatial association with macrophages/microglia. Together, our results identify a cytotoxic NK-like CD8+ T-cell subset that links peripheral inflammation to CNS lesions and may serve as an early biomarker of MS severity.