Age-related defects in Th1 and Th2 cytokine production by human T cells can be dissociated from altered frequencies of CD45RA + and CD45RO + T cell subsets

The present study investigated whether age-related changes in the production of Th1 and Th2 cytokines by human T cells might be linked to altered frequencies of naive (CD45RA +) and memory (CD45RO +) T cell subsets. T cells from healthy elderly humans ( n=32) stimulated with anti-CD3ε monoclonal antibody OKT3 plus PMA produced significantly lower levels of IL-2 and IFNγ (Th1 type) and of IL-4 (Th2 type) cytokines compared with T cells from young subjects. Although considerable heterogeneity was observed in the levels of cytokines produced by activated T cells from elderly individuals, linear regression analysis failed to demonstrate any significant shift in Th1 to Th2 type cytokine profiles of human T cells during aging. Sufficient T cells were available from eighteen elderly subjects to quantitate the levels of cytokine production in parallel with flow cytometry analysis of the frequencies of CD45RA + naive and CD45RO + memory T cells. Compared with the group of young subjects, the elderly group exhibited significant decreases in the frequencies of naive T cells with reciprocal increases in memory T cells. However, defects in Th1 and Th2 cytokine production were not significantly correlated with altered frequencies of naive/memory T cells among elderly individuals. In addition, those elderly individuals with normal frequencies of naive/memory T cells exhibited decreases in cytokine production comparable to the reductions observed for elderly donors with alterations in the frequencies of naive/memory T cells. These findings suggest that age-related defects in Th1 and Th2 cytokine production cannot be attributed entirely to alterations in the frequencies of naive/memory T cell subsets and point toward intrinsic aberrancies within human T cell cytokine networks during aging.