Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 09 04 1 13 Mona Tajrishi Department of Hematology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran Saeed Mohammadi Cell Therapy and Hematopoietic Stem Cell Transplantation Research Center, Research Institute for Oncology, Hematology and Cell Therapy, Tehran University of Medical Sciences, Tehran, Iran Mohammad Vaezi Cell Therapy and Hematopoietic Stem Cell Transplantation Research Center, Research Institute for Oncology, Hematology and Cell Therapy, Tehran University of Medical Sciences, Tehran, Iran Mohammad Ahmadvand Cell Therapy and Hematopoietic Stem Cell Transplantation Research Center, Research Institute for Oncology, Hematology and Cell Therapy, Tehran University of Medical Sciences, Tehran, Iran Saeid Abroun Department of Hematology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran 2026 04 17 2026 06 19 Regulatory T cells (Tregs) play a central role in maintaining immune tolerance and modulating inflammatory responses. Different cellular sources may give rise to Tregs with distinct phenotypic properties, which could influence their clinical applicability in immune-mediated diseases. In this exploratory comparative study, we performed a comparative flow cytometric analysis of Treg populations derived from mobilized peripheral blood (mPB) and umbilical cord blood (UCB). Tregs were identified based on a standard CD4+CD25+CD127low/− gating strategy, followed by phenotypic assessment using markers associated with differentiation (CD45RA/RO, CD27), activation (CD69), and immune checkpoint–related regulation (PD-1, TIM-3). Our results demonstrate source-dependent differences in the distribution of naive and memory-like Treg subsets, as well as in the expression of activation and checkpoint-associated markers. These preliminary findings suggest phenotypic heterogeneity between mPB- and UCB-derived Tregs and warrant validation in larger cohorts and functional studies. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4803 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4803/2416