Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 0 0 2026 07 11 1 10 Alireza Omidvar-Mehrabadi Infectious Diseases Research Center, Aja University of Medical Sciences, Tehran, Iran AND Medical Biotechnology Research Center, Aja University of Medical Sciences, Tehran, Iran AND Department of Immunology, School of Medicine, Babol University of Medical Sciences, Babol, Iran Mehdi Shakouri-Khomartash Infectious Diseases Research Center, Aja University of Medical Sciences, Tehran, Iran AND Medical Biotechnology Research Center, Aja University of Medical Sciences, Tehran, Iran Hasan Abedi Department of Internal Medicine, Rohani Hospital, Babol University of Medical Sciences, Babol, Iran Mojgan Mohammadi-Mehr Infectious Diseases Research Center, Aja University of Medical Sciences, Tehran, Iran AND Department of Laboratory Sciences, Faculty of Paramedicine, Aja University of Medical Sciences, Tehran, Iran Ali Faridfar Cancer Epidemiology Research Center, Aja University of Medical Sciences, Tehran, Iran Ali Shakeri-Moghaddam Infectious Diseases Research Center, Aja University of Medical Sciences, Tehran, Iran AND Medical Biotechnology Research Center, Aja University of Medical Sciences, Tehran, Iran 2025 12 07 2026 02 22 Peptic ulcer disease (PUD) is a common gastrointestinal disorder associated with chronic mucosal inflammation and immune dysregulation. Recent evidence suggests that Mucosal-associated invariant T (MAIT) cells, a subset of T cells expressing CD161 and Vα7.2, are involved in mucosal immunity and inflammatory responses. However, their precise role in PUD remains unclear. Given their dual function in immune defense and inflammation, investigating MAIT cell alterations in PUD could provide novel insights into disease pathogenesis and potential therapeutic targets. A cross-sectional study was performed, including 25 patients with endoscopically verified PUD and 25 healthy controls. Flow cytometry was used to quantify circulating MAIT cells (Vα7.2+CD161++) and their subsets (CD4+, CD8+, and double-negative). Serum interleukin-17 (IL-17) and interferon-γ (IFN-γ) levels were measured using ELISA in 21 PUD patients and 21 healthy controls. Correlations between MAIT cell frequencies and cytokine levels were analyzed using the Spearman correlation coefficient. PUD patients exhibited a substantially elevated frequency of circulating MAIT cells compared to controls. Among subsets, CD8+ MAIT cells showed the most pronounced increase, correlating positively with serum IFN-γ levels (r=0.5819). Furthermore, levels of IL-17 and IFN-γ were substantially elevated in individuals with PUD in comparison to controls. Our results indicate that MAIT cells, particularly the CD8+ subset, may contribute to immune activation in PUD. The observed increase in MAIT cells, along with elevated IL-17 and IFN-γ levels, highlights their potential involvement in disease progression. These findings support the potential role of MAIT cells as biomarkers or therapeutic targets in PUD. https://ijaai.tums.ac.ir/index.php/ijaai/article/view/4688 https://ijaai.tums.ac.ir/index.php/ijaai/article/download/4688/2366