Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 19 5 2020 10 18 509 516 EN Mona Oraei Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Sama Bitarafan Iranian Center of Neurological Research, Neuroscience Institute, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. Seyed Alireza Mesbah-Namin Department of Clinical Biochemistry, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Ali Noori-Zadeh Department of Clinical Biochemistry, Faculty of Allied Medical Sciences, Ilam University of Medical Sciences, Ilam, Iran. Fatemeh Mansouri Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Karim Parastouei Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. Ali Anissian Department of Veterinary Pathology, Islamic Azad University, Abhar, Iran Mir Saeed Yekaninejad Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Maryam Hajizadeh Department of Parasitology and Mycology, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran. Ali Akbar Saboor-Yaraghi Department of Immunology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Iranian Center of Neurological Research, Neuroscience Institute, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran 2020 04 09 2020 06 02 Vitamin D plays a variety of physiological functions, such as regulating mineral homeostasis. More recently, it has emerged as an immunomodulator player, affecting several types of immune cells, such as regulatory T (Treg) cells. It has been reported that vitamin D exerts some mediatory effects through an epigenetic mechanism. In this study, the impacts of calcitriol, the active form of vitamin D, on the methylation of the conserved non-coding sequence 2 (CNS2) region of the forkhead box P3 (Foxp3) gene promoter, were evaluated. Fourteen C57BL/6 mice were recruited in this study and divided into two intervention and control groups. The CD4+ T cells were isolated from mice splenocytes. The expression of Foxp3, IL-10, and transforming growth factor-beta (TGF-β1) genes were relatively quantified by real-time PCR technique, and the DNA methylation percentage of every CpG site in the CNS2 region was measured individually by bisulfite-sequencing PCR. Vitamin D Intervention significantly (p<0.05) could increase the expression of Foxp3, IL-10, and TGF-β1 gene in the CD4+ T cells of mice comparing with the control group. Meanwhile, methylation of the CNS2 region of Foxp3 promoter was significantly decreased in three of ten CpG sites in the vitamin D group compared to the control group. The results of this study showed that vitamin D can engage the methylation process to induce Foxp3 gene expression and probably Treg cytokines profile. Further researches are needed to discover the precise epigenetic mechanisms by which vitamin D modulates the immune system. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/2772