Use of a compound capable of reducing the activity of Core 2 GlcNAc-T in the manufacture of a medicament for the treatment of Multiple Sclerosis is disclosed. Also disclosed is a method of diagnosing Multiple Sclerosis in a subject and a method of determining the utility of a test substance for use in the treatment of Multiple Sclerosis comprising determining the ability of the substance to inhibit the activity of Core 2 GlcNAc-T.