CD274 and myeloid sarcoma: By using multiple immunostainings on highly inflamed MS brain tissues containing meningeal tertiary lymphoid structures (TLSs), we analyzed PD-L1 expression on EBV-infected cells expressing EBNA2, five EBV lytic gene products, BZLF1, BHRF1, BMRF1, BALF2, and gp350/220, as well as on follicular dendritic cells within the TLSs.