The purpose of this study was to determine whether BAFF levels: (i) were increased in MS patients in comparison to other neurological diseases (OND) and HC, (ii) were modified after Methylprednisolone therapy in MS patients (iii) were correlated to the humoral response against peptides from infectious agents, previously associated to MS: Epstein-Barr Virus (EBV) and Mycobacterium avium subsp. This evidence concerns the gene TNFSF13B and nervous system disorder.