Taken together with neuropathological evidence of active EBV infection in CNS-infiltrating B cells/plasma cells (19, 35, –, 39, 42) and the predominance of CD8 T cells with a cytotoxic effector phenotype in the MS brain (50, –, 53), the selective enrichment of EBV-specific CD8 T cells in postmortem MS brain samples reported here and in the CSF of MS patients (54, –, 57) supports a pathogenic model of MS where skewed cytotoxic immune responses toward EBV may contribute to inflammation in the CNS. The gene discussed is CD8A; the disease is myeloid sarcoma.