Decreased natural killer cell activity after prolonged administration of interferon in cancer patients.

Two patients with metastatic neoplastic disease received 2-3 X 10(6) IU alpha recombinant interferon (IFN) 3 times/wk, every other week, for 3-6 mth. The natural killer (NK) activity of their peripheral blood leukocytes, was followed during the course of the treatment. A significant decrease was observed in the NK activity, which returned to normal values at the end of IFN administration. The treatment did not modify the evolution of metastasis.