Sensitivity of natural killer cells to activation in the process of ageing is related to the oxidative and inflammatory status of the elderly.

ABSTRACT

The role of the innate immunity during human ageing is not well understood. The aim of the study was to estimate reactivity of NK (natural killer) cells in the very old (mean age 91 years) and old subjects (mean age 78 years) compared to young individuals (mean age 26 years) in respect to the indices of the oxidative stress (telomere length of NK cells, serum content of -H groups), serum total antioxidant status and serum concentrations of interleukin 6 and tumor necrosis factor-α (TNF-α). The activation state of NK cells, reflected by telomerase activity and intracellular interferon γ (IFNγ) content, was also measured. We found that length of telomeres in NK cells and serum concentration of -SH groups decreased both in the old and the oldest subjects as compared to young individuals. The oldest seniors, on the contrary to the old ones, revealed similar level of serum antioxidant status as the young subjects. The serum level of IL-6, not detectable in the young subjects, did not differ in the oldest and old seniors. TNF-α serum concentrations progressively increased with age. After stimulation, NK cells of both old groups showed higher intracellular levels of IFNγ than young subjects. IL-2-activated NK cells of the oldest seniors showed the highest increase of telomerase activity as compared to the other age groups. Serum level of IL-6 correlated positively with activation markers of NK cells. Moreover, in seniors but not in young subjects, the number of active, IFNγ-expressing NK cells, correlated positively with the serum content of the -SH groups. These findings indicate that sensitivity of NK cells to activation is maintained during ageing and this phenomenon may be related to the oxidative and inflammatory status of the elderly.