The primary objective of this study is to determine the effects of various therapies (immunomodulatory as well as immunosuppressive) on ATP levels in CD4+ cells and to determine whether the "ImmuKnow®" assay is an appropriate screening tool to assess the immunocompetence of potential Tysabri patients.
Secondary objective is to correlate the expression of ATP in CD4+ cells with CD4+ cell count.
Tertiary objective is to examine the level of regulatory T-cells (CD4+ and CD25+) in MS patients and its possible correlation to the therapy used, and how well a recently proposed marker of regulatory T-cells, LAP, correlates with CD25 marker.
