CD8A and myeloid sarcoma: In this study, we used postmortem brain tissue donated by persons with MS and in situ pentamer staining to (i) characterize the EBV antigens recognized by CNS-infiltrating CD8 T cells, (ii) compare the frequency of EBV-specific CD8 T cells with that of CD8 T cells recognizing other common viruses or a putative myelin autoantigen, and (iii) study the cytotoxic effector function of CNS-infiltrating, EBV-specific CD8 T cells and their spatial proximity to virus-infected B cells/plasma cells.