CD4 and myeloid sarcoma: In human, but not in mouse [91], CD28, an important co-stimulatory molecule expressed on T cells [92,93] and involved in the regulation of both tolerance and autoimmunity [94], has been also described to stimulate CD4+ T cells to produce inflammatory cytokines and chemokines related to the Th17 cell phenotype [95,96] and to enhance the inflammatory response in MS by reprogramming T cell metabolism and favoring the expression of Th17-associated cytokines [97,98].