The effect of ageing on human lymphocyte subsets: comparison of males and females.

BACKGROUND: There is reported to be a decline in immune function and an alteration in the frequency of circulating lymphocytes with advancing age. There are also differences in ageing and lifespan between males and females. We performed this study to see if there were differences between males and females in the frequency of the different lymphocyte subsets with age. RESULTS: Using flow cytometry we have examined different populations of peripheral blood leukocytes purified from healthy subjects with age ranging from the third to the tenth decade. We used linear regression analysis to determine if there is a linear relationship between age and cell frequencies. For the whole group, we find that with age there is a significant decline in the percentage of naïve T cells and CD8(+) T cells, and an increase in the percentage of effector memory cells, CD4(+)foxp3(+) T cells and NK cells. For all cells where there was an effect of ageing, the slope of the curve was greater for men than for women and this was statistically significant for CD8(+)alphabeta(+) T cells and CD3(+)CD45RA(-)CCR7(-) effector memory cells. There was also a difference for naïve cells but this was not significant. CONCLUSION: The cause of the change in percentage of lymphocyte subsets with age, and the different effects on males and females is not fully understood but warrants further study.

Frequency and function of regulatory T cells after ischaemic stroke in humans.

Ischaemic stroke is an important cause of disability and death. Local inflammation in the brain following stroke is thought to enhance damage. Animal studies show that regulatory T cells (Tregs) can downregulate this inflammation and assist recovery, but there are no previous studies of the function of Tregs in human stroke. The current study aimed to quantify Tregs in peripheral blood following stroke and to investigate their function. Treg numbers were significantly increased after stroke, particularly in males. However, the functional capacity of Tregs to inhibit proliferation of autologous cells at low ratios of Treg to responder cells was reduced, particularly in female patients, compared to controls. This study is the first to report gender-specific changes in the numbers and function of Tregs after ischaemic stroke. These changes may affect stroke outcome.