Tehran University of Medical Sciences Immunology and Genetics Journal 2645-4831 2 4 2019 12 01 173 184 Amir Ghasemi Department of Microbiology and Immunology, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran; Department of Infectious Disease and Immunology, College of Veterinary Medicine, University of Florida, FL, USA. 2019 10 19 Primary immunodeficiencies contain a set of several different diseases. Giving the fact that their clinical outcome ranges from mild to potentially life-threatening, detecting the patients with these diseases in the neonatal period is considered as the main goal of efforts that are currently being made. It has been reported that T-cell receptor excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs) are circular DNA segments produced in T and B cells during their maturation in the thymus and bone marrow, respectively. Fortunately, excision circles can be reliably quantified using real-time quantitative PCR techniques. https://igj.tums.ac.ir/index.php/igj/article/view/36 https://igj.tums.ac.ir/index.php/igj/article/download/36/25