Systemic administration of human leukocyte interferon to melanoma patients. I. Effects on natural killer function and cell population.

Natural killer (NK) cytotoxicity was assessed against K562 targets in 14 melanoma patients who received daily im doses of human leukocyte interferon (IFN) for 42 consecutive days. The most common pattern of NK activity was a decline from pretreatment levels 1 day after initiation of treatment, followed by increasing cytotoxicity with peak activity at day 7 and a subsequent gradual decline to pretreatment levels during the remaining weeks of treatment. This pattern was particularly apparent in patients who received 3 x 10(6) or 9 x 10(6) U IFN/day, while patients who received 1 X 10(6) U IFN/day tended to lack the decline at day 1 and maintained the elevated NK activity past day 7. Changes in NK activity could not be related to changes in absolute lymphocyte counts; to proportions of cells bearing membrane receptors for erythrocyte-antibody-complement, of cells bearing FC gamma receptor; or to clinical response to IFN.