Tehran University of Medical Sciences Immunology and Genetics Journal 2645-4831 6 1 2023 03 22 21 27 Hossein Sanjari Moghaddam School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Golshid Sanati Duke Center for Genomic and Computational Biology, Duke University School of Medicine, Durham, NC 27710, USA Maryam Sadr Research Center for Immunodeficiencies, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran Bahareh Mohebbi Research Center for Immunodeficiencies, Children's Medical Center, Tehran University of Medical Sciences, Tehran, Iran Mahsa Keshavarz-Fathi School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Roham Salmanroghani Shahid Sadoughi Hospital, Yazd University of Medical Sciences, Yazd, Iran Hassan Salmanroghani Shahid Sadoughi Hospital, Yazd University of Medical Sciences, Yazd, Iran Nima Rezaei Tehran University of Medical Sciences 2022 09 25 2022 10 01 Background: The pathogenesis of inflammatory bowel disease may be associated with the disruption in interactions between the immune system and gut flora. Epigenetic mechanisms especially, DNAmethylation appear to be significant regarding the interaction between the environment and genome. ABCB1 is the encoding gene for multi-drug resistance protein 1 (MDR1) (P-glycoprotein), which is an important transmembrane protein responsible for the efflux of cellular molecules from the intestinal wall to the lumen. Method: In this study, we compared the methylation status of the promoter of ABCB1 in rectal mucosa of patients with ulcerative colitis (UC) and healthy controls by using the bisulfite conversion system and real- time quantitative multiplex methylation-specific PCR (QM-MSP). Results: We demonstrated that the mucosal specimen of 26 UC patients had significantly higher levels of promoter methylation in comparison to 26 controls. Conclusion: As the first investigation of Iranian patients with UC, we showed that patients had higher levels of ABCB1 promoter methylation in their inflammatory rectal mucosa compared to controls. However, this altered state of methylation did not associate with the characteristics of the patients such as age and sex. Our findings are a basis for further studies on concurrent assessment of promoter methylation and expression of ABCB1 in UC. https://igj.tums.ac.ir/index.php/igj/article/view/103 https://igj.tums.ac.ir/index.php/igj/article/download/103/118