Human mucosal Vα7.2+ CD161hi T cell distribution at physiologic state and in Helicobacter pylori infection.

Mucosal-associated invariant T (MAIT) cells are innate-like, unconventional T cells that are present in peripheral blood and mucosal surfaces. A clear understanding of how MAIT cells in the mucosae function and their role in host immunity is still lacking. Therefore, our aim was to investigate MAIT cell distribution and their characteristics in the gastrointestinal (GI) mucosal tissue based on Vα7.2+ CD161hi identification. We showed that Vα7.2+ CD161hi T cells are present in both intraepithelial layer and lamina propriae of the GI mucosa, but have different abundance at each GI site. Vα7.2+ CD161hi T cells were most abundant in the duodenum, but had the lowest reactivity to MR1-5-OP-RU tetramers when compared with Vα7.2+ CD161hi T cells at other GI tissue sites. Striking discrepancies between MR1-5-OP-RU tetramer reactive cells and Vα7.2+ CD161hi T cells were observed along each GI tissue sites. Vα7.2+ CD161hi TCR repertoire was most diverse in the ileum. Similar dominant profiles of TRBV usage were observed among peripheral blood, duodenum, ileum, and colon. Some TRBV chains were detected at certain intestinal sites and not elsewhere. The frequency of peripheral blood Vα7.2+ CD161hi T cells correlated with mucosal Vα7.2+ CD161hi T cells in lamina propriae ileum and lamina propriae colon. The frequency of peripheral blood Vα7.2+ CD161hi T cells in Helicobacter pylori-infected individuals was significantly lower than uninfected individuals, but this was not observed with gastric Vα7.2+ CD161hi T cells. This study illustrates the biology of Vα7.2+ CD161hi T cells in the GI mucosa and provides a basis for understanding MAIT cells in the mucosa and MAIT-related GI diseases.

Mucosal-associated invariant T cells in clinical diseases.

UNLABELLED: Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognize microbial infection via vitamin metabolites. The discovery of MAIT cells in the past two decades and the recent discovery of MR1 ligands has opened a new field and potential area for cellular immunotherapy using these unique cells. Their evolutionary conservation in mammals underscore their biological role in the host. In the past two years, we have been involved in the generation of MR1 tetramers as a tool for identification of these cells. Many groups have studied the role of these cells in clinical diseases. OBJECTIVE: Here, we provide an up-to-date comprehensive review of clinical disease that have been studied with regards to MAIT cells. RESULTS: Original articles and review articles under the topic of MAIT cells and their relation to clinical diseases, both in human and animal models were included in the review. CONCLUSION: MAIT cells are potential candidates for future cellular immunotherapy. However, more understanding of the biological role of MAIT cells need to be elucidated first.