CD274 and myeloid sarcoma: We demonstrated that in the cerebral immune infiltrates of MS donors (i) PD-L1 is expressed on EBV latently infected LMP2A+ B lymphocytes, mainly accumulating in meningeal TLSs; (ii) T cells and, most importantly, EBV-specific CD8+ T cells express PD-1; and (iii) PD-1+ T cells establish close contacts with PD-L1+/LMP2A+ latently infected cells.