CD4 and myeloid sarcoma: Clinical studies in multiple sclerosis patients with natalizumab, a humanized monoclonal IgG4 VLA4 blocking antibody approved for MS, have shown that the drug not only increases the number of CD4+ and CD8+ T cells in the peripheral blood39 but also stimulates CD4+ and CD8+ T cell production of more IL-2, TNF-α, IFN-γ, and IL-1740–43.