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Mech Ageing Dev 2000 Sep 29;118(3):129-44.
Natural killer (NK) cells are a critical first line of defense against viral infections and tumors. We showed previously that basal NK cytotoxicity was comparable in adult (6 month) and aged (24 month) C57BL/6 (B6) mice. However, NK activity was significantly higher in adult compared with aged B6 mice after either in vitro or in vivo stimulation with IFN-alpha/beta. The present study explored whether age-related decreases in inducible NK activity after stimulation with IFN-alpha/beta were due to differences in (1) IFN-alpha/beta receptor expression or IFN-alpha/beta binding to NK cells or (2) apoptosis of NK cells. Flow cytometry revealed that, despite significantly higher IFN-alpha/beta receptor expression (Paged mice, IFN-alpha/beta binding to NK cells was comparable between adult and aged mice. In addition, IFN-alpha/beta treatment significantly increased Fas (CD95) expression (Paged mice. However, after IFN-alpha/beta stimulation, NK cells from aged mice demonstrated significantly higher CD95 expression (Ppercent apoptosis (Pstimulation may include altered IFN-alpha/beta receptors and/or increased percentages of NK cells undergoing apoptosis.