Thymopoiesis and regulatory T cells in healthy children and adolescents

objectives: the purpose of this study was to investigate the association between t cell receptor excision circle levels in peripheral blood mononuclear cells and regulatory t cells that co-express cd25 and foxp3 in healthy children and adolescents of different ages. materials and methods: the quantification of signal-joint t-cell receptor excision circle levels in the genomic dna of peripheral blood mononuclear cells was performed using real-time quantitative pcr. the analysis of cd4, cd8, cd25, and foxp3 expression was performed using flow cytometry. results: ninety-five healthy controls (46 females and 49 males) ranging in age from 1 to 18 years were analyzed. the mean t-cell receptor excision circle count in all individuals was 89.095？36.790 t-cell receptor excision circles per microgram of dna. there was an inverse correlation between t-cell receptor excision circles counts and age (r = -0.846; p<0.001) as well as between the proportion of cd4+cd25+foxp3+ t cells and age (r = -0.467; p = 0.04). in addition, we observed a positive correlation between the amount of cd4+cd25+foxp3+ t cells and the amount of tcell receptor excision circles per microgram of dna in individuals of all ages (r = -0.529; p = 0.02). conclusions: in this study, we observed a decrease in the thymic function with age based on the fact that the level of t-cell receptor excision circles in the peripheral blood positively correlated with the proportion of regulatory t cells in healthy children and adolescents. these findings indicate that although t-cell receptor excision circles and regulatory t cells levels decrease with age, homeostasis of the immune system and relative regulatory t cells population levels are maintained in the peripheral blood.