Interleukin 2- and interferon alpha induced natural killer cell activity as a marker of progression in hairy cell leukemia.

Hairy cell leukemia (HCL), a rare B-cell chronic lymphoproliferative disorder, is often accompanied by immune abnormalities. A marked impairment of the natural killer cell-mediated cytotoxicity (NK activity) has been reported in most patients at diagnosis. In the present report a long-term follow-up study of NK activity of splenectomized HCL patients is recorded. Among patients who persisted with stable disease two groups, one with normal NK activity, and another with low NK activity, could be recognized. Patients with progressive stage were characterized by a low NK cytotoxic activity. In vitro tests showed that interferon alpha (IFN-alpha) and interleukin 2 (IL2) could increase the NK activity to normal levels only in HCL patients with stable disease, while in progressive HCL these cytokines showed a significantly decreased effect. These results indicate that cytokine-induced NK cytotoxicity appears to be a valuable parameter in assessing the stage of HCL.