Twin study identifies early immunological and metabolic dysregulation of CD8+ T cells in multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory neurological disease of the central nervous system with a subclinical phase preceding frank neuroinflammation. CD8⁺ T cells are abundant within MS lesions, but their potential role in disease pathology remains unclear. Using high-throughput single-cell RNA sequencing and single-cell T cell receptor analysis, we compared CD8⁺ T cell clones from the blood and cerebrospinal fluid (CSF) of monozygotic twin pairs in which the cotwin had either no or subclinical neuroinflammation (SCNI). We identified peripheral MS-associated immunological and metabolic alterations indicative of an enhanced migratory, proinflammatory, and activated CD8⁺ T cell phenotype, which was also evident in cotwins with SCNI and in an independent validation cohort of people with MS. Together, our in-depth single-cell analysis indicates a disease-driving proinflammatory role of infiltrating CD8⁺ T cells and identifies potential immunological and metabolic therapeutic targets in both prodromal and definitive stages of the disease.