Natural killer cell activity in patients with multiple sclerosis: interferon and plasmapheresis

Peripheral blood lymphocytes from patients with multiple sclerosis (MS) were studied for natural killer (NK) cell activity and reactivity to interferon. NK activity determined at the same time in a 4-hr chromium-51 release assay using K562 target cells was significantly lower in MS patients than in controls. In-vitro treatment of MS lymphocytes with interferon resulted in only a slight increase in NK activity, while NK activity of normal individuals was markedly augmented by interferon. Leukopheresis of MS patients gave a rapid decrease in cytotoxic activity, which returned to pretreatment levels by 24 hrs. These results are consistent with the hypothesis of an immune deficit in multiple sclerosis.