The Turkish Journal of Pediatrics 2023 , Vol 65 , Num 1
Evaluation of thymopoiesis in healthy Turkish children aged 0-6 years
Akif Kavgacı 1 ,Deniz Bayrakoğlu 2 ,Sevgi Köstel Bal 2 ,Şule Haskoloğlu 2 ,Nisa Eda Çullas İlarslan 1 ,Seda Topçu 3 ,Emel Okulu 4 ,Candan İslamoğlu 2 ,Meltem Arıkan 2 ,Figen Doğu 2 ,Kamile Aydan İkincioğulları 2
1 Department of Pediatrics, Ankara University Faculty of Medicine, Ankara
2 Department of Pediatric Immunology and Allergy, Ankara University Faculty of Medicine, Ankara
3 Department of Social Pediatrics, Ankara University Faculty of Medicine, Ankara
4 Department of Neonatology, Ankara University,Faculty of Medicine, Ankara, Türkiye
DOI : 10.24953/turkjped.2021.5190 Background. Early diagnosis and effective treatment serve as life-saving procedures for primary immunodeficiencies (PIDs) which are very common and a major public health problem in Turkey. Severe combined immunodeficiency (SCID) is constitutively a T-cell defect in which naïve T-cell development is defective due to the mutations in genes responsible for the T cell differentiation and insufficient thymopoiesis. So, assessment of thymopoiesis is very important in the diagnosis of SCID and several combined immune deficiencies (CIDs).

Methods. The purpose of this study is to examine thymopoiesis in healthy children via measurement of recent thymic emigrants (RTE); T lymphocytes that express CD4, CD45RA and CD31 to establish the RTE reference values in Turkish children. RTE were measured in the peripheral blood (PB) of 120 healthy infants and children between 0-6 years including cord blood samples, by flow cytometry.

Results. The absolute count of RTE cells and their relative ratios were found to be higher during the first year of life, being highest at the 6th month and tending to decrease significantly by age following birth (p=0.001). In the cord blood group, both values were lower than those in the 6-month-old group. The absolute lymphocyte count (ALC) varying by age, was found to reduce to 1850/mm³ in 4-years and after.

Conclusions. Here we evaluated normal thymopoiesis and established the normal reference levels of RTE cells in the peripheral blood of healthy children aged between 0-6 years. We believe that the collected data will contribute to early diagnosis and monitoring of immune reconstitution; serving as an additional fast and reliable marker for many PID patients especially for SCID including many other CIDs, especially in nations where newborn screening (NBS) via T cell receptor excision circles (TREC) has not yet become available. Keywords : recent thymic emigrants (RTE), thymopoiesis, flow cytometry

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