In this context, peripheral blood as a mirror of immune reaction in CNS is much easier to measure longitudinally. CD4+ T cells and later CD4 + Th1 cells are the most studied cell populations in MS  because of their potential role in the pathogenesis of the disease, as well as they are used to assess the effect of different therapies used in MS. More recently, regulatory subpopulations such as Th2 cells, regulatory CD4+ T cells and NK cells were studied for their relationship in disease prognosis  and radiologically confirmed MS activity. Changes in their effector populations were described . The association of CD4 + CD45RO+ IL-17A+ cells to clinical and radiological disease activity was reported. [17, 18] Differences in naive CD4 T-cell biology, notably in TCR and TLR signalling pathways, identified patients with MS with more rapid conversion to secondary progression .