Multiple Sclerosis CD49dCD154 As Myelin-Specific Lymphocytes Induced During Remyelination.

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system (CNS) mediated by autoreactive lymphocytes. The role of autoreactive lymphocytes in the CNS demyelination is well described, whereas very little is known about their role in remyelination during MS remission. In this study, we identified a new subpopulation of myelin-specific CD49dCD154 lymphocytes presented in the peripheral blood of MS patients during remission, that proliferated in vitro in response to myelin peptides. These lymphocytes possessed the unique ability to migrate towards maturing oligodendrocyte precursor cells (OPCs) and synthetize proinflammatory chemokines/cytokines. The co-culture of maturing OPCs with myelin-specific CD49dCD154 lymphocytes was characterized by the increase in proinflammatory chemokine/cytokine secretion that was not only a result of their cumulative effect of what OPCs and CD49dCD154 lymphocytes produced alone. Moreover, maturing OPCs exposed to exogenous myelin peptides managed to induce CD40-CD154-dependent CD49dCD154 lymphocyte proliferation. We confirmed, in vivo, the presence of CD49dCD154 cells close to maturating OPCs and remyelinating plaque during disease remission in the MS mouse model (C57Bl/6 mice immunized with MOG) by immunohistochemistry. Three weeks after an acute phase of experimental autoimmune encephalomyelitis, CD49d/CD154 cells were found to be co-localized with O4 cells (oligodendrocyte progenitors) in the areas of remyelination identified by myelin basic protein (MBP) labelling. These data suggested that myelin-specific CD49dCD154 lymphocytes present in the brain can interfere with remyelination mediated by oligodendrocytes probably as a result of establishing proinflammatory environment.