 The purpose of this work is to investigate the influence of dietary salt intake on immune function in multiple sclerosis MS subjects and healthy controls. This study primarily tests the hypothesis that higher dietary salt intake will be associated with a higher frequency of pathogenic Th17 cells and impaired function of protective regulatory T cells. If a relationship between dietary salt intake and immune function is observed, this study will also test: a whether this relationship is unique to MS subjects or whether it is also present in healthy controls, and b whether healthier immune function can be restored by restricting dietary salt intake. 