Embodiments of this invention include methods for detecting in vitro the presence of Memory B cells in peripheral blood mononuclear cells (PBMCs) that produce antibodies reactive to CNS antigens associated with Multiple Sclerosis (MS). Stimulating PBMCs from patients with MS by a polyclonal stimulating agent promotes the ability of B-lymphocytes, when exposed to a CNS antigen, to produce antibodies specific for the CNS antigen. In contrast, stimulating PBMCs from subjects without MS do not produce such responses.