Age-Related Changes in Subpopulations of Peripheral Blood Lymphocytes in Healthy Japanese Population

Abstract

Peripheral blood mononuclear cells were obtained from healthy Japanese individuals ranging in age from 20 to 90 years old and analyzed by using three color flow cytometer with regards to the number and percentage of various lymphocytes. In addition, we assessed the proliferative capacity of T-cells in the presence of an anti-CD3 monoclonal antibody and the amount of cytokines produced in the supernatant.

The results showed that an age-related decline was observed in the numbers of CD3⁺ T-cells, CD8⁺ T-cells, naive T-cells, CD8⁺CD28⁺ T-cells, and B-cells and in the proliferative capacity of T-cells. The rate of decline in these immunological parameters except for the number of CD8⁺ T-cells was steeper in males than in females (p <0.05). An age-related increase was observed in the number of CD4⁺ T-cells, memory T-cells, and NK-cells and in the CD4/CD8 ratio. The rate of increase of these immunological parameters was steeper in females than in males (p <0.05). The T-cell proliferation index (TCPI), which was calculated based on T-cell proliferative activity and the number of T-cells, showed an age-related decline. The rate of decline in the TCPI was again steeper in males than in females (p <0.05). The score of immunological vigor calculated using 5 T-cells parameters also declined with age, and the rate of decline was steeper in males than in females (p <0.05). The present study has confirmed the age-related changes in immunological parameters reported in literature. In addition, we found that a statistically significant gender difference was observed between males and females in some immunological parameters such as the number of T-cells and TCPI. The slower rate of decline in the immunological parameters studied in females than in males may be consistent with the fact that women survive for longer period of time than men.