In this one-year longitudinal observational study, by assessing changes in circulating lymphocyte compositions of 40 patients with relapsing MS treated with natalizumab, we demonstrated a significant increase in absolute numbers of all major populations, most markedly for NK cells and B cells, as well as restored CD4+ and CD8+ T cell responsiveness to recall antigens and mitogens. This evidence concerns the gene CD4 and myeloid sarcoma.