Successful ageing of nonagenarians is related to the sensitivity of NK cells to activation.

NK cells are a component of innate immunity which activity significantly correlates with health status. The aim of our study was to estimate a status of NK (natural killer) cells in the very old (mean age 92+/-2 ys) and old subjects (mean age 78+/-5 ys) as compared to a control group of young individuals (mean age 25+/-4 ys). NK cells were characterized by measurement of their cytotoxic activity, expression of intracellular interferon gamma, telomere length and telomerase activity in resting and activated cells. The results revealed that the oldest seniors did not differ from the other age groups in the number of NK cells and NK cytotoxic activity, however, they displayed the shortest telomeres and the lowest telomerase activity. Surprisingly, activated NK cells of the very old, similarly to the old subjects, were able to significantly increase intracellular level of IFNgamma. Moreover, activated with IL-2 NK cells of the old and oldest seniors showed increased telomerase activity. The results of our study suggest that the functional status of NK cells and their sensitivity to activation is well preserved until very advanced age and may contribute to longevity and successful ageing.