Abstract: To explore the relationship between T cells and aging. Methods15 mice were divided into three groups: the 2-month (young), the 6 -month (middleaged) and the 15-month (aged) groups. Splenocyte suspensions were prepared in sterile conditions. Surface marks were stained with the PECy5-conjugated CD4 antibody and the FITC-conjugated CD25 antibody. After being washed with PBS, cells were treated with stiletto fluid and fixation fluid and stained with the PE-conjugated Foxp3 antibody. The proportion of CD4⁺ regulatory T cells was analyzed by flow cytometry. ResultsThe proportion of CD4⁺ T cells and CD4⁺ CD25⁺ /CD4⁺ T cells in splenocytes had no significant differences among the three groups. But the proportion of CD4⁺ Foxp3⁺ T cells was significantly elevated with an increase of age. The proportion of CD4+ Foxp3+ T cells was(16.83±0.44)% in aged mice, which was obviously higher than young and middle-aged mice（P＜0.01）, and the proportion of CD25⁺ Foxp3⁺ regulatory T cells gradually decreased. The proportion of CD25⁺ Foxp3⁺ T cells in the aged group or in middle-aged mice was lower than that in young mice（P＜0.05）.　However, the proportion of CD25^- Foxp3⁺ regulatory T cells continuously elevated with an increase of age. Its proportion in aged mice was significantly higher than that in middle-aged mice(P＜0.01), and that in middle-aged mice was higher than that in young mice(P＜0.01). In addition, the ratio of CD4⁺ CD25⁺ Foxp3⁺ T to CD4⁺ CD25^- Foxp3⁺ T cells showed a decreasing tendency with an increase of age. ConclusionThe proportion of CD4⁺ CD25⁺ Foxp3⁺ T cells shows an decreasing tendency with an increase of age, however, the proportion of CD4⁺ CD25^- Foxp3⁺ T cells shows an increasing tendency. These suggest that the two regulatory subsets play different roles in aging.

Key words: CD4⁺ CD25⁺ Foxp3⁺ T cell , CD4⁺ CD25^- Foxp3⁺ T cell, Aging, Flow cytometry