CD8A and myeloid sarcoma: By single-cell RNA sequencing of CSF cells, Beltrán and colleagues (82) recently showed that clonally expanded CD8 T cells can be detected in the CSF of MS discordant monozygotic twins with subclinical neuroinflammation defined by presence of small MRI lesions and CSF alterations, supporting early involvement of activated CD8 T cells in MS immunopathogenesis.