AGE-RELATED INCREASE IN THE FRACTION OF CD27-CD4+ T-CELLS AND IL-4 PRODUCTION AS A FEATURE OF CD4+ T-CELL DIFFERENTIATION IN-VIVO

The influence of ageing on phenotype and function of CD4(+) T cells was studied by comparing young (19-28 years of age) and aged (75-84 years of age) donors that were selected using the SENIEUR protocol to exclude underlying disease. An age-related increase was observed in the relative number of memory cells, not only on the basis of a decreased CD45RA and increased CD45RO expression, but also on the basis of a decrease in the fraction of CD27(+)CD4(+) T cells. Our observation that the absolute number of CD45RO(+)CD4(+) T cells was increased, while absolute numbers of CD27(-)CD4(+) T cells remained unchanged in aged donors, indicates that the latter subset does not merely reflect the size of the CD45RO(+)CD4(+) T cell pool. The increased fraction of memory cells in the aged was functionally reflected in an increased IL-4 production and T cell proliferation, when cells were activated with the combination of anti-CD2 and anti-CD28, whereas IL-2 production was comparable between both groups. No differences were observed with respect to proliferative T cell responses or IL-2 production using plate-bound anti-CD3 or phytohaemagglutinin (PHA). The observation that IL-4 production correlated with the fraction of memory cells in young donors but not in aged donors suggests different functional characteristics of this subset in aged donors.