AGE-DEPENDENT CHANGES OF T-REGULATORY AND Th17 SUBSET LEVELS IN PERIPHERAL BLOOD FROM HEALTHY HUMANS

Age-dependent development of Th17 and Treg lymphocyte subsets in healthy humans is studied insufficiently. The present study aimed to investigate quantitative characteristics of Th17 and Treg subsets in peripheral blood of healthy subjects for various age groups.352 healthy humans (168 female and 184 male), one month to 85 years old, were subject to examination, including 79 infants in their first year of life; 34 children at aged 1 year to 2 years 11 months; 24, at 3 to 4 years 11 months; 28, at the age of 5 to 6 years 11 months; 25 children aged 7-8 years 11 month; 36 children aged 9 to 11 years 11 months; 39 adolescents aged 12 to 14 years 11 months; 26 adolescents aged 15 to 18 years; 25 young adults aged 20 to 35 years; 11 adults at 36 to 49 years old; 16 adults aged 59-70 years, and 9 elderly people over 70 years old. The study was performed with capillary blood in children under 2 years, and venous blood taken in elder persons. The basic and ‘minor’ subsets of peripheral blood lymphocytes were evaluated by flow cytometry using four-color staining of whole blood and following erythrocyte lysis. We used the following surface markers: CD3, CD4, CD8, CD25, CD127, CD161, CD45R0 for lymphocyte subsets detection.It has been shown that Treg percentage (a ratio of CD4+CD25hiCD127low/neg in the CD3+CD4+ gate) did not depend on age of the people under study, and can be approximated by a linear function. The absolute number of Tregs in childhood is progressively decreased and, after 10 years old, it reaches plateau values. This age-dependent relationship may be approximated by a logarithmic function. Evaluation of Th17 subset levels demonstrated a strong relative and absolute age-dependent growth of this cell subpopulation. Percentage and absolute numbers of Th17 lymphocyte (share of CD4+CD161+CD45R0+ in the CD3+CD4+gate), can be approximated by a square function. The age of 10-12 years seems to be critical to the immune system formation. We suppose the process of the immune system development to be completed at this age, and maturation of the immune cell populations is then observed. A decrease in both relative and absolute numbers of Treg and Th17 lymphocyte subsets was found in elderly persons (> 70 years old). Our data on peripheral blood Tregs and Th17 subsets, with respect to their percentage and absolute numbers in healthy humans, may be used as age-related reference values.