In post-mortem MS cases, a role for virus-driven immunopathology is evident with the finding of tissue-resident memory (Trm) T cells, a subset of CD8+ T cells, that establish direct contact with EBV infected cells in the infiltrated MS white matter and meninges, including the TLO (Serafini et al., 2023). The gene discussed is CD8A; the disease is myeloid sarcoma.