Natural killer cell numbers and function in peripheral lymphoid cells in Behcet's disease.

We have studied NK cell activity and numbers in the peripheral blood obtained from patients with Behcet's disease and from normal healthy controls. NK cell activity in the peripheral blood of patients in the clinically-active stage of Behcet's disease was significantly lower than that of patients in the inactive stage and normal controls. In contrast, it was observed that the actual number of NK cells was markedly increased in the peripheral blood of patients with active disease. The addition of alpha-interferon (INF-alpha) to these cells showed significant augmentation of NK cell activity. These results suggest that the patients with active Behcet's disease lack a factor which activates NK cells.