Abstract: Objective To investigate the effects of aging on the expression of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg), CD4⁺T cells in human peripheral blood and the levels of cytokines. Methods The absolute counts of CD4⁺T cells and CD4⁺CD25⁺Foxp3⁺ Treg, and the levels of interleukin-2 (IL-2), interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), IL-10 and IL-17 were measured respectively in peripheral blood of 40 young persons (20-45 years old), 40 middle-aged persons (50-75 years old) and 40 elderly persons (above 80 years old), and also the percentage of CD4⁺CD25⁺Foxp3⁺Treg in CD4⁺T cells in peripheral blood of the three groups was calculated. The differences among the three groups were compared. Results The absolute count of CD4⁺T cells in peripheral blood decreased significantly in the elderly group than those in the young group and the middle-aged group(P<0. 05). The absolute count of CD4⁺CD25⁺Foxp3⁺Treg was significantly higher in peripheral blood in the elderly group and the middle-aged group than that in the young group(P<0. 05). The percentage of CD4⁺CD25⁺Foxp3⁺Treg in CD4⁺T cells was the highest in the elderly group, followed by the middle-aged group and the young group (P<0. 05). The levels of IL-2, IFN-γ and IL-17 in the elderly group were significantly lower than those in the young group and the middle-aged group (P<0. 05), and the level of IL-2 in the middle-aged group was significantly lower than that in the young group (P<0. 05). The level of IL-10 in the elderly group was significantly higher than that in the young group and the middle-aged group (P<0. 05), and the level of TNF-α among the three groups showed no significant difference (P>0. 05). Conclusions The absolute count of CD4⁺CD25⁺Foxp3⁺Treg in peripheral blood increases significantly after middle-age. With the increase of age, the ratio of CD4⁺CD25⁺Foxp3⁺Treg/CD4⁺T cells increases significantly. In the elderly, the absolute count of CD4⁺T cells and the levels of IL-2, IFN-γ, IL-17 decrease significantly, while the level of IL-10 significantly increases, indicating that the immune function of the elderly further decreases and the microenvironment is changed.

Key words: aging, CD4⁺CD25⁺Foxp3 regulatory T cell, CD4⁺T cells, cytokines