The present invention relates to the diagnosis, the prevention and the treatment of demyelinating disorders of the central nervous system (CNS), in particular disorders exhibiting altered levels of antibodies directed against α1-3-galactose, such as multiple sclerosis (MS) and clinically isolated syndrome (CIS). The diagnosis of MS and CIS still suffers from a lack of reliable biomarkers and there is cure for these diseases, except medication acting on the immune component of the overt disease, with the usual side effects of the immunosuppression or anti inflammation intended to relieve the associated symptoms. The inventors showed that there is a significant decrease in the levels of antibodies directed against α1-3-galactose in individuals having a MS or a CIS. In addition, the present invention relates to the prevention and/or the treatment of a demyelinating disorder of the CNS in an individual, comprising a step of administering a compound suitable for generating an immune reaction directed against α1-3-galactose in the said individual. Large cohorts of human individuals having MS or CIS have been studied and compared to matched cohorts on the basis of age and gender.La présente invention concerne le diagnostic, la prévention et le traitement de troubles de démyélinisation du système nerveux central (SNC), en particulier des troubles présentant des taux modifiés d'anticorps dirigés contre l'α 1-3-galactose, tels que la sclérose en plaques (SP) et le syndrome clinique isolé (SCI). Le diagnostic de la SP et du SCI souffre encore d'un manque de biomarqueurs fiables, et il y a un remède pour ces maladies, sauf que les médicaments agissant sur l'élément immunitaire de la maladie déclarée donnent lieu aux effets secondaires habituels de l'immunosuppression ou de l'anti-inflammation, destinées à soulager les symptômes associés. Les inventeurs ont montré qu'il y a une diminution significative des taux d'anticorps dirigés contre l'α 1-3-galactose chez des individus atte
