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Expansion of CD28null effector memory and effector T cells expressing higher levels of NK associated receptors in healthy elderly

We have previously studied that the T cells show a decrease in the expression of CD28 in the elderly, associated with an increase of the expression of some NK-R in the CD28 negative subsets. The aim of this work is to analyse the telomere length in the different lymphocyte subsets from PBMCs from healthy elderly donors compared with young. Our results show that the CD28 negative subsets are significantly increased in the elderly. This increase is associated with a shortening in the telomere length when compared with the CD28 negative subset from young donors. We have also found no significant differences in the NK phenotype between young and elderly.

This result is completed by the finding that there are no differences between telomere lengths from the healthy elderly NK subsets when compared with the young NK subset. When the CD28 positive subset was analysed, we found that the telomere length was significantly longer both in young and elderly donors comparing with the CD28 counterpart.

These results support the hypothesis that these cells are cytotoxic T cells that has undergone a process of replicative senescence. We have also analysed the different memory subsets based on simultaneous staining for CD45RA and CCR7 , lymphocytes described as subsets that could be segregated into so called naive (CD45RA+CCR7+), central-memory (CD45RA-CCR7+), effector-memory (CD45RA-CCR7-) and effector (CD45RA+CCR7-) T lymphocytes.

The aim of this work is to analyse the expression of CD56, CD94, CD244, CD28 on CD8 T cells associated with the memory phenotype (based on CD45RA and CCR7 phenotype). The results show us that in healthy donors the CD8+CD28+ subset is mainly represented by the naive subset, while the CD8+CD28- subset, are mainly represented by the effector subset. We have also found that the CD244 cytotoxicity surface marker is significantly expressed on the memory effector subset, while the expression of CD56 and CD94 markers is higher in the effector subset and lower in the naive subset. When the CD8+CD56+ subset was analysed, we found that this cytotoxic subset is mainly represented by the effector phenotype.

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