Alpha-interferon activates the natural killer system in patients with hairy cell leukemia.

To elucidate the mechanisms of alpha-interferon's (alpha-INF) therapeutic effect on clinical and laboratory findings in hairy cell leukemia, we sequentially monitored different immunologic parameters in three patients treated with recombinant alpha-INF. The most evident effect of this treatment on the immune system was the recovery of natural killer (NK) cell in vitro activity of peripheral blood lymphocytes, which was severely impaired before therapy. In particular, NK function began to improve after 3 months, and a complete recovery was obtained after 6 months in all cases. This increase parallels the improvement in clinical and laboratory findings.