A quantitative increase of leukocyte Leu7+ subset (largely represented by cells with natural killer activity, NK) was observed in the peripheral blood mononuclear cells of patients during the active period of cluster headache (CH). These patients are susceptible to herpes virus infections. In order to ascertain whether or not the quantitative changes in Leu7+ leukocyte subset would correspond to changes of the NK function, the activity of NK cells was investigated in CH patients. Eighteen patients with the episodic form of CH were studied during cluster periods and in painless periods. The control group consisted of 11 healthy volunteers. The results show that the NK activity of CH patients is significantly lower in comparison to that of control values. This impairment appears to be independent of the cluster period.
Since β-IFN has been shown to increase “in vitro” NK cell activity, studies were performed to investigate if β-IFN could restore the limited NK activity found in CH patients. For this purpose the “in vitro” effect of overnight incubation with β-IFN (1000 I.U./ml) was assessed on NK cell activity in CH patients and in the control group. It was found that β-IFN was more effective in increasing NK activity of effector cells collected from CH patients when compared with healthy controls.