Interestingly, the secretion of serotonin by platelets has been demonstrated to stimulate differentiation of T cells toward pathogenic Th1, Th17, and interferon-γ/interleukin-17–producing CD4 T cells in a stage-depended manner: Early in MS and EAE, high levels of platelet-derived serotonin stimulate differentiation of pathogenic T cell subsets, promoting proinflammatory responses (165). This evidence concerns the gene CD4 and myeloid sarcoma.