Natural killer cell activity in multiple sclerosis patients treated with recombinant interferon-alpha 2.

Natural killer (NK) cell activity was evaluated in multiple sclerosis (MS) patients during a phase II trial of recombinant interferon-alpha 2 (IFN). Spontaneous NK activity against the K562 myeloid target cell increased significantly during the first week of treatment in the IFN treatment group. However, NK activity was also increased in the placebo treatment group. Long-term administration of IFN caused a decline of NK activity, below the pretreatment values. This decline was not paralleled by a decline in the percentage of Leu-7 cells in the peripheral blood. The ability of IFN to enhance NK activity during treatment was also evaluated. Enhancement of NK activity by IFN was depressed for the duration of the study in the IFN treatment group. After treatment was stopped, IFN enhancement of NK activity returned to the pre-study value. These studies demonstrate that spontaneous and IFN enhanced NK activity are profoundly affected by the administration of recombinant IFN-alpha 2 in MS patients.