Thymopoiesis and regulatory T cells in healthy children and adolescents.
OBJECTIVE
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.


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 T-cell 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.
Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo, Departamento de Pediatria, Instituto da Criança, Brasil.
Maria Izabel
MI
Arismendi
Esper Georges
EG
Kallás
Bianca Almeida Natali dos
BA
Santos
Magda Maria Sales
MM
Carneiro-Sampaio
Cristiane
C
Kayser
D000293:Adolescent; D000367:Age Factors; D001327:Autoimmune Diseases / Q000276:immunology*; D015704:CD4 Antigens / Q000032:analysis; D018791:CD4 Lymphocyte Count; D016827:CD8 Antigens / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D005260:Female; D051858:Forkhead Transcription Factors / Q000032:analysis*; D006801:Humans; D007223:Infant; D053645:Interleukin-2 Receptor alpha Subunit / Q000032:analysis*; D008297:Male; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism; D013950:Thymus Gland / Q000276:immunology* / Q000378:metabolism
D015704:CD4 Antigens; D016827:CD8 Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; C508017:IL2RA protein, human; D053645:Interleukin-2 Receptor alpha Subunit; D011948:Receptors, Antigen, T-Cell