Lightning Talk & Poster Presentation CD1-MR1 Workshop 2025

MAIT cells represent a major population of antibacterial tissue-resident memory T (TRM) cells in the human gastrointestinal tract (#42)

Xingchi Chen 1 , Chuyao Chen 1 , Fei Han 1 , Zhengyu Wu 1 , Dan He 1 , Huizhong Xu 1 , Yingqian Zhong 2 , Yifang Gao 2 , Edwin Leeansyah 1
  1. Institute of Biopharmaceutical and Health Engineering, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China
  2. Organ Transplantation Centre, Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China

Introduction

Tissue-resident memory T (TRM) cells provide frontline defense, maintain homeostasis, and support tissue repair in the human gastrointestinal (GI) tract. However, their role in antibacterial immunity in the human gut remains poorly understood. Mucosa-associated invariant T (MAIT) cells are a large subset of antibacterial T cells that recognize bacterial riboflavin metabolites and are enriched in barrier tissues, including the human gut. Yet, their identity as an antibacterial TRM population and the mechanisms guiding their tissue residency remain unclear.

 

Methods

Tissue-resident (TR)-MAIT cells were isolated from the duodenum, ileum, appendix, and sigmoid colon of healthy organ donors for transcriptomic and flow cytometry profiling. Peripheral blood MAIT cells were cultured with various enteric bacteria and tissue-derived factors in 2D cell culture and 3D human intestinal organoid systems to generate TR-MAIT-like cells.

 

Results

MAIT cells constituted a significant TRM population across multiple gut sites. Transcriptomic and phenotypic profiling revealed that TR-MAIT cells express canonical tissue-residency markers, including CD49a, CD69, CD103, CXCR3, and CXCR6, while lacking egress-associated molecules such as S1PR1. Circulating MAIT cells partially expressed tissue-residency features and differentiated into TR-MAIT-like cells in vitro upon exposure to bacterial riboflavin metabolites and tissue factors. TCR stimulation combined with RARα or RARγ signalling is required to generate TR-MAIT-like cells. These cells displayed antimicrobial functions, expressed tissue-homing markers tailored to local cues, and produced tissue-repair cytokines and antimicrobial cytolytic molecules upon stimulation. TR-MAIT-like cells were also generated through direct contact with human intestinal organoids in 3D cultures. Notably, among T cell subsets cultured with gram-negative enteric bacteria, MAIT cells emerged as a predominant TRM population.

 

Conclusion

Our findings identify MAIT cells as a significant antibacterial TRM subset in the healthy human gut. Future studies will elucidate the mechanisms driving their tissue residency and define their contributions to infectious and inflammatory conditions of the gastrointestinal tract.