In 1986, Mossman and Coffman  presented the concept of distinct T helper cell subsets and MS was later considered a CD4+ Th1-mediated autoimmune disease  but not surprisingly the T-cell biology in vivo is more complex than a simple dichotomy. In addition to Th1/Th2, the Th17 subset and different classes of regulatory T cells (Treg) are involved in MS. Recent studies have shown that the T cells mediating MS can be heterogeneous, with Th17 cells predominating in some individuals and Th1 cells in others  The plasticity of different T cell subsets and emerging evidence that subset-signature cytokine expression is not as stable as initially believed  strongly support our attempt to find a more reliable marker as a predictor of conversion to CDMS.