EFFECTS OF AGING ON NATURAL-KILLER-CELL ACTIVITY AND ACTIVATION BY INTERLEUKIN-2 AND IFN-ALPHA

To address the conflicting reports concerning both innate and lymphoki ne-inducible NK activity of elderly individuals, NK activity of periph eral blood mononuclear cells (PBMC) of 21 young (23 to 35 years old) a nd 43 elderly (65 to 100 years old) subjects was assessed using a 4-hr chromium release assay with K562 or Daudi cells as targets. Significa ntly higher-innate NK cell activity was observed in elderly compared t o young individuals (P < 0.001, Student t test). NK activity of both g roups was enhanced to the same degree by IL-2. Although intermediate a mounts of IFN-alpha (100-500 u/10(6) cells) induced comparable maximal NK activity of both young and elderly subjects, young subjects respon ded better than elderly to low amounts of IFN-alpha (10 u/10(6) cells) , while higher amounts (10(3) u/10(6) cells) reduced the NK activity o f the elderly, but not young, to basal level. IFN-alpha also expanded the range of target cells susceptible to NK activity. Untreated cells of neither young nor elderly showed activity against Daudi targets. Tw o-hour treatment with IFN-alpha resulted in significant activity again st Daudi cells; however, this activity was significantly lower in the elderly compared to the young subjects. (C) 1994 Academic Press, Inc.