Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 18 2 2019 04 01 143 152 EN Leila Shakerian Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran Zahra Pourpak Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran Somayeh Shamlou Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran Erna Domsgen ImmunoIVD, Nacka Strand, Nacka, Sweden Anoshirvan Kazemnejad Department of Biostatistics, Tarbiat Modares University, Tehran, Iran Hossein Dalili Breastfeeding Research Center, Tehran University of Medical Sciences, Tehran, Iran Maryam Nourizadeh Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran 2018 04 15 2018 06 19 Assessment of the number of T-cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) copies has been recently described as biomarkers of newly formed T and B cells respectively. In this study, we aimed to explore the effects of demographic variables including age, gender, weight, height and ethnicity on these two episomal DNA molecules. Second, for the first time in our country, we determined the reference values of TREC and KREC copy numbers in different age groups of Iranian healthy individuals as a threshold for identifying T cell and B cell lymphopenia. The TREC and KREC copy numbers were evaluated in 251 dried blood spot (DBS) samples from healthy volunteers (age range: 0-60 years). Six primary immunodeficiency (PID) patients were included as disease controls. TREC and KREC copies were markedly reduced with increasing age. Although the levels of TREC and KREC were higher in females than males, this difference did not reach statistical significance. These findings suggest that demographic variables including age should be considered for interpretation results of the TREC/KREC assay. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/1907 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/1907/1409