Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 02 11 1 13 Pouria Ghiaee Department of Immunology, School of Medicine, Kerman University of Medical Sciences, Kerman, Iran Sarehsadat Ebrahimi Department of Immunology and Allergy, Kerman University of Medical Sciences, Kerman, Iran Seyed Alireza Mahdaviani Pediatric Respiratory Disease Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran Fatemeh Tarighat Monfared Pediatric Respiratory and Sleep Medicine Research Center, Children’s Medical Center Hospital, Tehran Universityof Medical Sciences, Tehran, Iran Marzieh Tavakol Non-Communicable Diseases Research Center, Alborz University of Medical Sciences, Karaj, Iran Mehrdad Dargahi Mal-Amir Air Pollution and Respiratory Diseases Research Center, Ahvaz Jundishapur University of Medical Center, Ahvaz, Iran Nima Rezaei Research Center for Immunodeficiencies, Pediatrics Center of Excellence, Children's Medical Center Hospital, Tehran University of Medical Sciences, Tehran, Iran AND Primary Immunodeficiency Diseases Network (PIDNet), Universal Scientific Education and Research Network (USERN), Tehran, Iran Abdollah Jafarzadeh Department of Immunology, School of Medicine, Kerman University of Medical Sciences, Kerman, Iran 2025 03 15 2025 08 31 Common variable immunodeficiency disease (CVID) is the most prevalent symptomatic inborn errors of immunity, determined by defective B cell function, impaired antibody production, and susceptibility to frequent respiratory infections, enteropathy, autoimmunity, and malignancy. Due to the importance of autoimmunity in CVID and the probable role of regulatory B lymphocytes, we aimed to determine the frequency of B10 cells in CVID patients with and without autoimmunity. A total of 24 CVID patients and 12 healthy controls were enrolled in the study. Patients were divided into two equal groups, with and without autoimmunity. Peripheral blood cells were stained with monoclonal antibodies (mAbs) to identify CD24hiCD38hi B cells, CD27int CD38+ (plasmablasts), and CD24hiCD27+ B cells by flow cytometry. The percentages of B10, CD24hiCD27+ and CD27int CD38+ cells were significantly lower in total CVID patients, CVID patients with autoimmunity and CVID patients without autoimmunity compared to healthy controls (mean±standard deviation (SD) percentage of B10 cells: 6.36±9.21(total CVID), 2.81±5.00 (CVID with autoimmunity), and 3.25±3.5 (CVID without autoimmunity) vs. 13.02±12.45 (healthy controls); CD24hiCD27+ cells: 2.39±3.89, 3±5.20 and 1.78±1.94 vs. 20.38±14.27; CD27int CD38+ cells: 6.80±18.49, 7.40±20.24 and 6.20±17.45 vs. 11.84±5.71). CVID patients without autoimmunity had a higher percentage of CD24hiCD38hi cells than CVID patients with autoimmunity (4.73±4.14 vs. 2.62±5.02). The defect of regulatory B cells plays a significant role in the pathogenesis of autoimmunity in CVID. Further multicenter studies with higher sample sizes are suggested to determine the role of Breg cells in the clinical course of autoimmunity.  https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4386 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4386/2306