CXCL13 and myeloid sarcoma: The high levels of CXCL13 in the CSF or ELFS of MS patients, along with other proteins associated with lymphoid follicles such as activation-induced cytidine deaminase (AICDA) [39] and proliferating B cells, such as Ki67+ centroblasts [40], are all consistent with the hypothesis that ELFs in the meninges of MS patients have a major role in the disease.