CD4 and myeloid sarcoma: Naive B cells that have escaped this control most likely mature and differentiate into T-bet+ class-switched memory B cells by interacting with infectious triggers and IFN-γ-producing CD4+ T follicular helper (TFH) cells.20, 21, 22, 23 Within the periphery, these B cells mainly function as potent antigen presenting cells to stimulate IFN-γ-producing brain-homing CD4+ T cells in MS.24