Plasmapheresis not only removes humoral factors, but may also modulate cellular immunity. We investigated whether plasmapheresis influenced T helper type-1/T helper type-2 (Th1/Th2) cytokine-producing-cell balance in 3 patients with neuroimmunological disease. The production of interferon-gamma (IFN-gamma), interleukin-2 (IL-2), and IL-4 in the culture supernatant of peripheral blood mononuclear cells stimulated by anti-CD3 and anti-CD28 was assayed. In 2 of 3 patients, plasmapheresis (immunoadsorption or plasma exchange) reduced Th1/Th2 cytokine ratio. The results may suggest that plasmapheresis induces a shift of Th1/Th2 balance in peripheral blood.