CD8A and myeloid sarcoma: By showing that fewer inactive MS patients have a detectable CD8+ T cell response against EBV lytic antigens compared with HD and active MS patients and that the frequency of lytic antigen-specific CD8+ T cells is higher in active MS patients than in HD and inactive MS patients, we demonstrate for the first time that changes in the immune control of EBV replication are associated with the active and inactive phases of MS.