Age-related increase in the fraction of CD27−CD4+ T cells and IL-4 production as a feature of CD4+ T cell differentiationin vivo

Abstract

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 CO45RA 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 anli-CD2 and anti-CD28, whereas lL-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.