CXCR3 and myeloid sarcoma: In this study, we reveal that high EBV load is associated with (1) early emergence of CXCR3+ class‐switched memory B cells from autologous BMT‐treated MS patients, and (2) enhanced in vitro generation of CXCR3+ plasma cells from memory B cells trapped in the blood of NTZ‐treated MS patients.