MOG and myeloid sarcoma: Although anti-MOG antibodies were initially associated with conversion to MS, they were later linked to a distinct entity, MOGAD, rather than MS.252,253 Nevertheless, the formation of tertiary lymphoid structures in the meninges of MS patients, where B and T cells interact and B cells mature, indicates sustained secretion of antibodies into the CNS and strongly supports the contribution of B cells to the immunopathogenic mechanisms of MS.254