Mucosal-associated Invariant T Research Articles

Prostaglandins differentially modulate mucosal-associated invariant T-cell activation and function according to stimulus.

Mucosal-associated invariant T (MAIT) cells are an innate-like T-cell type conserved in many mammals and especially abundant in humans. Their semi-invariant T-cell receptor (TCR) recognizes the major histocompatibility complex-like molecule MR1 presenting riboflavin intermediates associated with microbial metabolism. Full MAIT cell triggering requires costimulation via cytokines, and the cells can also be effectively triggered in a TCR-independent manner by cytokines [e.g. interleukin (IL)-12 and IL-18 in combination]. Thus, triggering of MAIT cells is highly sensitive to local soluble mediators. Suppression of MAIT cell activation has not been well explored and could be very relevant to their roles in infection, inflammation and cancer. Prostaglandins (PG) are major local mediators of these microenvironments which can have regulatory roles for T cells. Here, we explored whether prostaglandins suppressed MAIT cell activation in response to TCR-dependent and TCR-independent signals. We found that protaglandin E2 (PGE2 ) and to a lesser extent protaglandin D2 (PGD2 ), but not leukotrienes, suppressed MAIT cell responses to Escherichia coli or TCR triggers. However, there was no impact on cytokine-induced triggering. The inhibition was blocked by targeting the signaling mediated via PG receptor 2 (PTGER2) and 4 (PTGER4) receptors in combination. These data indicate that prostaglandins can potentially modulate local MAIT cell functions in vivo and indicate distinct regulation of the TCR-dependent and TCR-independent pathways of MAIT cell activation.

Graft-versus-Host Disease Modulation by Innate T Cells

Allogeneic cell therapies, defined by genetically mismatched transplantation, have the potential to become a cost-effective solution for cell-based cancer immunotherapy. However, this type of therapy is often accompanied by the development of graft-versus-host disease (GvHD), induced by the mismatched major histocompatibility complex (MHC) between healthy donors and recipients, leading to severe complications and death. To address this issue and increase the potential for allogeneic cell therapies in clinical practice, minimizing GvHD is a crucial challenge. Innate T cells, encompassing subsets of T lymphocytes including mucosal-associated invariant T (MAIT) cells, invariant natural killer T (iNKT) cells, and gamma delta T (γδ T) cells, offer a promising solution. These cells express MHC-independent T-cell receptors (TCRs), allowing them to avoid MHC recognition and thus GvHD. This review examines the biology of these three innate T-cell populations, evaluates research on their roles in GvHD modulation and allogeneic stem cell transplantation (allo HSCT), and explores the potential futures for these therapies.

Th1 bias of liver mucosal-associated invariant T cells promotes hepatic gluconeogenesis in type 2 diabetes mellitus.

It is acknowledged that aberrant liver immunity contributes to the development of type 2 diabetes mellitus (T2DM). Mucosal-associated invariant T (MAIT) cells, an innate-like T-cell subset, are enriched in the human liver. Nevertheless, the characterisation and potential role of hepatic MAIT cells in T2DM remain unclear. Fourteen newly diagnosed T2DM subjects and 15 controls received liver biopsy. The frequency and cytokine production of MAIT cells were analysed by flow cytometry. The expression of genes involved in glucose metabolism was determined in HepG2 cells co-cultured with hepatic MAIT cells. Compared with controls, hepatic MAIT cell frequency was significantly increased in T2DM patients (24.66% vs. 14.61%, p=0.001). There were more MAIT cells producing interferon-γ (IFN-γ, 60.49% vs. 33.33%, p=0.021) and tumour necrosis factor-α (TNF-α, 46.84% vs. 5.91%, p=0.021) in T2DM than in controls, whereas their production of interleukin 17 (IL-17) was comparable (15.25% vs. 4.55%, p=0.054). Notably, an IFN-γ+ TNF-α+ IL-17+/- producing MAIT cell subset was focussed, which showed an elevated proportion in T2DM (42.66% vs. 5.85%, p=0.021) and positively correlated with plasma glucose levels. A co-culture experiment further indicated that hepatic MAIT cells from T2DM upregulated the gene expression of pyruvate carboxylase, a key molecule involved in gluconeogenesis, in HepG2 cells, and this response was blocked with neutralising antibodies against IFN-γ and TNF-α. Our data implicate an increased Th1-like MAIT cell subset in the liver of newly diagnosed T2DM subjects, which induces hyperglycaemia by promoting hepatic gluconeogenesis. It provides novel insights into the immune regulation of metabolic homoeostasis. NCT03296605 (registered at www. gov on 12 October 2018).

Targeted multi-omic analysis of human skin tissue identifies alterations of conventional and unconventional T cells associated with burn injury.

Burn injuries are a leading cause of unintentional injury, associated with a dysfunctional immune response and an increased risk of infections. Despite this, little is known about the role of T cells in human burn injury. In this study, we compared the activation and function of conventional T cells and unconventional T cell subsets in skin tissue from acute burn (within 7 days from initial injury), late phase burn (beyond 7 days from initial injury), and non-burn patients. We compared T cell functionality by a combination of flow cytometry and a multi-omic single-cell approach with targeted transcriptomics and protein expression. We found a significantly lower proportion of CD8+ T cells in burn skin compared to non-burn skin, with CD4+ T cells making up the bulk of the T cell population. Both conventional and unconventional burn tissue T cells show significantly higher IFN-γ and TNF-α levels after stimulation than non-burn skin T cells. In sorted T cells, clustering showed that burn tissue had significantly higher expression of homing receptors CCR7, S1PR1, and SELL compared to non-burn skin. In unconventional T cells, including mucosal-associated invariant T (MAIT) and γδ T cells, we see significantly higher expression of cytotoxic molecules GZMB, PRF1, and GZMK. Multi-omics analysis of conventional T cells suggests a shift from tissue-resident T cells in non-burn tissue to a circulating T cell phenotype in burn tissue. In conclusion, by examining skin tissue from burn patients, our results suggest that T cells in burn tissue have a pro-inflammatory rather than a homeostatic tissue-resident phenotype, and that unconventional T cells have a higher cytotoxic capacity. Our findings have the potential to inform the development of novel treatment strategies for burns.

Multi-Omics Analysis Reveals Intratumor Microbes as Immunomodulators in Colorectal Cancer.

Recent studies indicated that intratumor microbes are an essential part of the tumor microenvironment. Here, we performed an integrated analysis of genetic, epigenetic, and intratumor microbial factors to unravel the potential remodeling mechanisms of immune-cell infiltration (ICI) and tumorigenesis of colorectal cancer (CRC). We identified the components and structure of the intratumor microbiome as primary contributors to the difference in survival between ICI subtypes. Multiple tumor-infiltrating immune cells (TIICs) and immune-related genes were associated with intratumor microbial abundance. Additionally, we found that Clostridium was enriched in CRC patients who were nonsensitive to immune checkpoint blockade (ICB) therapy. We further provided clues that the intratumor microbes might influence the response to ICB therapy by mediating TIICs, especially MAIT (mucosa-associated invariant T) cells. Finally, three ICB-related TIICs and 22 of their associated microbes showed the potential to predict the response to ICB therapy (area under the receiver operating characteristic curve [AUC] = 89%). Our findings highlight the crucial role of intratumor microbes in affecting immune-cell infiltration patterns, prognosis, and therapy response of CRC and provide insights for improving current immunotherapeutic treatment strategies and prognosis for CRC patients. IMPORTANCE Using the multi-omics data from The Cancer Genome Atlas (TCGA) colorectal cancer (CRC) cohort, we estimated the tumor microenvironment (TME) infiltration patterns of patients and unraveled the interplay of gene expression, epigenetic modification, and the intratumor microbiome. This study suggests the impact of intratumor microbes on maintaining the tumor immune microenvironment in the pathogenesis of CRC and modulating the response to immune checkpoint blockade (ICB) therapy. We identified a set of combined features, including 3 ICB-related tumor-infiltrating immune cells (TIICs) and 22 of their associated microbes, that are predictive of ICB responses.

Increased IFN-γ+ and TNF-α+ mucosal-associated invariant T cells in patients with aplastic anemia.

Aplastic anemia (AA) is known as an autoimmune disease in which T cell activation is aberrant. It has been reported that unconventional T cells, mucosal-associated invariant T (MAIT) cells, play an important role in several autoimmune diseases, but it is unclear if they are involved in AA. In this study, we for the first time analyzed the proportions, phenotypes, and cytokine properties of MAIT cells in AA by flow cytometry. We found that the percentage of circulating MAIT cells was generally higher for CD3+ , CD8+ , and CD8- T cells in AA patients compared with healthy individuals. Moreover, the percentage of IL-18Rα-, NKG2D-, IFN-γ-, and TNF-α- positive MAIT cells was also significantly higher in AA patients. In addition, the percentage of IFN-γ+ CD3+ or TNF-α+ CD8- MAIT cells had a significant negative correlation with the absolute neutrophil count. We present the first observation of MAIT cells in patients with AA. MAIT cells are associated with a higher frequency of IFN-γ and TNF-α production and may contribute to the pathogenesis of AA.

RIPK3 controls MAIT cell accumulation during development but not during infection

Cell death mechanisms in T lymphocytes vary according to their developmental stage, cell subset and activation status. The cell death control mechanisms of mucosal-associated invariant T (MAIT) cells, a specialized T cell population, are largely unknown. Here we report that MAIT cells express key necroptotic machinery; receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL) protein, in abundance. Despite this, we discovered that the loss of RIPK3, but not necroptotic effector MLKL or apoptotic caspase-8, specifically increased MAIT cell abundance at steady-state in the thymus, spleen, liver and lungs, in a cell-intrinsic manner. In contrast, over the course of infection with Francisella tularensis, RIPK3 deficiency did not impact the magnitude of the expansion nor contraction of MAIT cell pools. These findings suggest that, distinct from conventional T cells, the accumulation of MAIT cells is restrained by RIPK3 signalling, likely prior to thymic egress, in a manner independent of canonical apoptotic and necroptotic cell death pathways.

Dysregulation of innate cell types in the hepatic immune microenvironment of alcoholic liver cirrhosis.

The risk of alcoholic cirrhosis increases in a dose- and time-dependent manner with alcohol consumption and ethanol metabolism in the liver. Currently, no effective antifibrotic therapies are available. We aimed to obtain a better understanding of the cellular and molecular mechanisms involved in the pathogenesis of liver cirrhosis. We performed single-cell RNA-sequencing to analyze immune cells from the liver tissue and peripheral blood form patients with alcoholic cirrhosis and healthy controls to profile the transcriptomes of more than 100,000 single human cells and yield molecular definitions for non-parenchymal cell types. In addition, we performed single-cell RNA-sequencing analysis to reveal the immune microenvironment related to alcoholic liver cirrhosis. Hematoxylin and eosin, Immunofluorescence staining and Flow cytometric analysis were employed to study the difference between tissues and cells with or without alcoholic cirrhosis. We identified a fibrosis-associated M1 subpopulation of macrophages that expands in liver fibrosis, differentiates from circulating monocytes, and is pro-fibrogenic. We also define mucosal-associated invariant T (MAIT) cells that expand in alcoholic cirrhosis and are topographically restricted to the fibrotic niche. Multilineage modeling of ligand and receptor interactions between the fibrosis-associated macrophages, MAIT, and NK cells revealed the intra-fibrotic activity of several pro-fibrogenic pathways, including responses to cytokines and antigen processing and presentation, natural killer cell-mediated cytotoxicity, cell adhesion molecules, Th1/Th2/Th17 cell differentiation, IL-17 signaling pathway, and Toll-like receptor signaling pathway. Our work dissects unanticipated aspects of the cellular and molecular basis of human organ alcoholic fibrosis at the single-cell level and provides a conceptual framework for the discovery of rational therapeutic targets in liver alcoholic cirrhosis.

Longitudinal analysis of mucosa-associated invariant T cells in sepsis reveals their early numerical decline with prognostic implications and a progressive loss of antimicrobial functions.

Sepsis-elicited immunosuppression elevates the risk of secondary infections. We used a clinically relevant mouse model and serial peripheral blood samples from patients to assess the antimicrobial activities of mucosa-associated invariant T (MAIT) cells in sepsis. Hepatic and splenic MAIT cells from B6-MAITCAST mice displayed increased CD69 expression and a robust interferon-γ (IFNγ) production capacity shortly after sublethal cecal ligation and puncture, but not at a late timepoint. Peripheral blood MAIT cell frequencies were reduced in septic patients at the time of intensive care unit (ICU) admission, and more dramatically so among nonsurvivors, suggesting the predictive usefulness of early MAIT cell enumeration. In addition, at ICU admission, MAIT cells from sepsis survivors launched stronger IFNγ responses to several bacterial species compared with those from patients who subsequently died of sepsis. Of note, while low human leukocyte antigen (HLA)-DR+ monocyte frequencies, widely regarded as a surrogate indicator of sepsis-induced immunosuppression, were gradually corrected, the numerical insufficiency of MAIT cells was not resolved over time, and their CD69 expression continued to decline. MAIT cell responses to bacterial pathogens, a major histocompatibility complex-related protein 1 (MR1) ligand, and interleukin (IL)-12 and IL-18 were also progressively lost during sepsis and did not recover by the time of ICU/hospital discharge. We propose that MAIT cell dysfunctions contribute to post-sepsis immunosuppression.

DOP08 Cellular and molecular interaction of MAIT in mucosal tissue and their role in inflammatory bowel disease

Abstract Background Inflammatory bowel disease (IBD) manifests as chronic inflammation of the gastrointestinal tract and is characterized by a deregulated immune response targeting the gut microflora. Mucosal-associated invariant T (MAIT) cells have been identified as a possible key player in IBD. Activated MAIT cells produce cytokines including IL-26, a newly discovered cytokine involved in the pathology of IBD. Interestingly, IL-26 is not expressed in mice and therefore its effect on the course of inflammation has not been yet fully investigated. Similarly, studies employing human cell cultures often provide limited results as they cannot fully mimic the complex three-dimensional structure of the intestinal tissue. A great hope is placed in the development of models of human diseases using organoids - 3D structures that better recapitulate the architecture and functionality of tissues. Methods Our laboratory recently described a model of intestinal inflammation based on human iPSCs-derived intestinal organoids (IOs). Taking advantage of this model, we investigate the influence of the cytokine IL-26 on the course of IBD. Moreover, we elucidate the influence of MAIT cells on the pathogenesis of IBD by studying their pathways of activation in vitro, and subsequently their interaction with inflamed tissues through the co-culture with IOs. Results After stimulation, IOs mimic the pro-inflammatory microenvironment and express various cytokines and chemokines. Moreover, IOs express MR1 which is recognised by the invariant TCR receptor of the MAIT cells. IOs express functional IL-26 receptor and respond to this cytokine. MAIT cells isolated from human blood show production cytokines including IL-26 and effector molecules upon in vitro activation. Their response differs depending on the origin of the stimuli. Conclusion IOs form complex structures and immunocompetent environment allowing to study of intestinal inflammation. IOs consist of various cell types, but not immune cells. Taken together with MR1 and cytokines expression we show that IOs can activate MAIT cells, and they serve as a relevant model for in vitro study of their biology. Moreover, IOs respond to IL-26, so they also provide a relevant model to elucidate the role of this cytokine. We expect that this study will contribute to our understanding of the processes underlying the progression of IBD, and lead to the design of new therapeutic targets for the treatment of idiopathic intestinal inflammation.

DOP01 The effect of vedolizumab on CD8 T cell repertoire homogeneity and blood-gut trafficking in patients with inflammatory bowel disease

Abstract Background Inflammatory bowel disease (IBD) causes T cell to infiltrate intestinal mucosa, but the heterogeneity of these cells is not understood at a clonal level. The anti-integrin α4β7 agent vedolizumab is believed to treat IBD by blocking this T cell infiltration from blood. Methods To understand the clonal distribution of T cells in IBD and how this is affected by vedolizumab, we studyined the T cell receptor (TCR) repertoire in CD8+ T cell subsets sorted from blood samples and colon mucosal biopsies via FACS. Inflamed or uninflamed colon segments from 15 ulcerative colitis and 13 Crohn’s disease patients were compared to colon biopsies from 11 people without IBD. In peripheral blood, we profiled purified α4β7+, α4β7- effector/memory, CD45RA+ terminal effector/memory (TEMRA) CD8 T cells, and mucosal-associated invariant T (MAIT) cells. In a separate cohort of 13 IBD patients, samples were obtained before and during vedolizumab therapy to determine its effect on the diversity and overlap of the TCR repertoires of blood and colon CD8+ T cells. Results CD8 TCR diversity in the mucosa and peripheral blood did not correlate with inflammation. CD8 TCR repertoire overlap between any two anatomically distinct locations of a person’s colon was consistently high, though often lower between inflamed and uninflamed sites. Repertoire overlap was also seen between the colon and each peripheral blood subpopulation studied, with the highest overlap seen for integrin α4β7+ T cells and the lowest for MAIT cells. Inflamed tissue overlapped more than uninflamed with each blood subpopulation. Vedolizumab did not affect the overlap between colon CD8+ T cells and circulating α4β7+ CD8 T cells, nor their TCR diversity, regardless of treatment efficacy. Indeed, flow cytometry revealed no relative depletion of effector/memory T cells in the colons of vedolizumab recipients. Instead, vedolizumab caused the depletion of rare naïve mucosal T cells and dendritic cells (DC) from the colonic mucosa. Conclusion CD8 T cell clones are spread homogenously throughout the colon. Although TCR repertoire overlap is greater within than between inflamed and uninflamed colon segments, a similar diversity of TCRs in both argues against local clonal expansion being the main source of excess T cells in inflamed mucosa. Rather, our data reveal increased TCR overlap between blood and inflamed mucosa to support the significance of T cell trafficking in IBD pathogenesis, particularly concerning experienced α4β7+ T cell populations. However, we surprisingly found neither gross nor clonal evidence that blockade of this trafficking is the mechanism by which vedolizumab treats IBD, instead finding only naïve T cells and DC to be depleted from the colonic mucosa in response to vedolizumab.

Depletion of polyfunctional CD26highCD8+ T cells repertoire in chronic lymphocytic leukemia

BackgroundCD8+ T cells play an essential role against tumors but the role of human CD8+CD26+ T cell subset against tumors, in particular, haematological cancers such as chronic lymphocytic leukemia (CLL) remains unknown. Although CD4+CD26high T cells are considered for adoptive cancer immunotherapy, the role of CD8+CD26+ T cells is ill-defined. Therefore, further studies are required to better determine the role of CD8+CD26+ T cells in solid tumors and haematological cancers.MethodsWe studied 55 CLL and 44 age-sex-matched healthy controls (HCs). The expression of CD26 on different T cell subsets (e.g. naïve, memory, effector, and etc.) was analyzed. Also, functional properties of CD8+CD26+ and CD8+CD26− T cells were evaluated. Finally, the plasma cytokine/chemokine and Galectin-9 (Gal-9) levels were examined.ResultsCD26 expression identifies three CD8+ T cell subsets with distinct immunological properties. While CD26negCD8+ T cells are mainly transitional, effector memory and effectors, CD26lowCD8+ T cells are mainly naïve, stem cell, and central memory but CD26high T cells are differentiated to transitional and effector memory. CD26+CD8+ T cells are significantly reduced in CLL patients versus HCs. CD26high cells are enriched with Mucosal Associated Invariant T (MAIT) cells co-expressing CD161TVα7.2 and IL-18Rα. Also, CD26high cells have a rich chemokine receptor profile (e.g. CCR5 and CCR6), profound cytokine (TNF-α, IFN-γ, and IL-2), and cytolytic molecules (Granzyme B, K, and perforin) expression upon stimulation. CD26high and CD26low T cells exhibit significantly lower frequencies of CD160, 2B4, TIGIT, ICOS, CD39, and PD-1 but higher levels of CD27, CD28, and CD73 versus CD26neg cells. To understand the mechanism linked to CD26high depletion, we found that malignant B cells by shedding Galectin-9 (Gal-9) contribute to the elevation of plasma Gal-9 in CLL patients. In turn, Gal-9 and the inflammatory milieu (IL-18, IL-12, and IL-15) in CLL patients contribute to increased apoptosis of CD26high T cells.ConclusionsOur results demonstrate that CD26+ T cells possess a natural polyfunctionality to traffic and exhibit effector functions and resist exhaustion. Therefore, they can be proposed for adoptive cancer immunotherapy. Finally, neutralizing and/or inhibiting Gal-9 may preserve CD26highCD8+ T cells in CLL.

THE EFFECT OF VEDOLIZUMAB ON CD8 T CELL REPERTOIRE HOMOGENEITY AND BLOOD-GUT TRAFFICKING IN PATIENTS WITH INFLAMMATORY BOWEL DISEASE

Abstract BACKGROUND Inflammatory bowel disease (IBD) causes T cell infiltration of the intestinal mucosa, but the heterogeneity of these cells is not understood at a clonal level. The drug vedolizumab is believed to treat IBD by blocking the entry of circulating integrin α4β7+ T cells into the intestinal mucosa. METHODS We sought to understand the clonal distribution of T cells in IBD and how this is affected by vedolizumab by studying the T cell receptor (TCR) repertoire in CD8+ T cell subsets sorted from blood samples and colon mucosal biopsies via FACS. Inflamed or uninflamed colon segments from 15 ulcerative colitis and 13 Crohn’s disease patients were compared to colon biopsies from 11 people without IBD. In peripheral blood, we profiled purified α4β7+, α4β7- effector/memory, CD45RA+ terminal effector/memory (TEMRA) CD8 T cells, and mucosal-associated invariant T (MAIT) cells. In a separate cohort of 13 IBD patients, samples were obtained before and during vedolizumab therapy to determine its effect on the diversity and overlap of the TCR repertoires of blood and colon CD8+ T cells. RESULTS CD8 TCR diversity in the mucosa and peripheral blood did not correlate with inflammation. Repertoire overlap between any two anatomically distinct locations of a person’s colon was consistently high, though often lower between inflamed and uninflamed sites. CD8 TCR repertoire overlap was also seen between the colon and each peripheral blood subpopulation studied, with the highest overlap seen for integrin α4β7+ T cells and the lowest for MAIT cells. Inflamed tissue overlapped more than uninflamed with each blood subpopulation. Surprisingly, vedolizumab did not affect the degree of overlap between colon CD8+ T cells and circulating α4β7+ CD8 T cells, nor their TCR diversity, regardless of treatment efficacy. Indeed, flow cytometry revealed no relative depletion of effector/memory T cells in the colons of vedolizumab recipients. Instead, vedolizumab caused the depletion of rare naïve mucosal T cells and dendritic cells (DC) from the colonic mucosa. CONCLUSIONS CD8 T cell clones are spread homogenously throughout the colon. Although TCR repertoire overlap is greater within than between inflamed and uninflamed colon segments, a similar diversity of TCRs in both argues against local clonal expansion being the main source of excess T cells in inflamed mucosa. Rather, our data reveal increased TCR overlap between blood and inflamed mucosa to support the significance of T cell trafficking in IBD pathogenesis, particularly concerning experienced α4β7+ T cell populations. However, we surprisingly found neither gross nor clonal evidence that blockade of this trafficking is the mechanism by which vedolizumab treats IBD, instead finding only naïve T cells and DC to be depleted from the colonic mucosa in response to vedolizumab.

MAITabolism2 - the emerging understanding of MAIT cell metabolism and their role in metabolic disease.

Mucosal associated invariant T (MAIT) cells are a population of unconventional innate T cells due to their non-MHC restriction and rapid effector responses. MAIT cells can recognise bacterial derived antigens presented on the MHC-like protein via their semi-restricted T cell receptor (TCR). Upon TCR triggering MAIT cells rapidly produce a range of effector molecules including cytokines, lytic granules and chemokines. This rapid and robust effector response makes MAIT cells critical in host responses against many bacterial pathogens. MAIT cells can also respond independent of their TCR via innate cytokines such as interleukin (IL)-18, triggering cytokine production, and are important in anti-viral responses. In addition to their protective role, MAIT cells have been implicated in numerous inflammatory diseases, including metabolic diseases often contributing to the pathogenesis via their robust cytokine production. Effector cells such as MAIT cells require significant amounts of energy to support their potent responses, and the type of nutrients available can dictate the functionality of the cell. Although data on MAIT cell metabolism is just emerging, several recent studies are starting to define the intrinsic metabolic requirements and regulators of MAIT cells. In this review we will outline our current understanding of MAIT cell metabolism, and outline their role in metabolic disease, and how disease-related changes in extrinsic metabolism can alter MAIT cell responses.

Characterization of Mucosal-Associated Invariant T Cells in Oral Lichen Planus.

Oral lichen planus (OLP) is an inflammatory condition of unknown cause that has been associated with concurrent candidal infection. Mucosal-associated invariant T (MAIT) cells express the T cell receptor TCRVα7.2 and are activated by riboflavin intermediates produced by microbes. The interaction between MAIT cells, Candida, and OLP is unknown. This study aimed to determine mucosal-associated T cell presence in OLP and whether the abundance of these cells changed due to the presence of either Candida or symptoms, using multiplex immunohistochemistry (mIHC). Ninety formalin fixed-paraffin-embedded (FFPE) tissue samples were assessed using mIHC for the cellular markers CD3, interleukin 18 receptor one (IL18R1), TCRVα7.2, CD161, CD8, and major histocompatibility complex class I-related (MR-1) protein. The samples were stratified into five groups on the basis of clinical (presence/absence of symptoms) and microbiological (presence/absence of Candida) criteria. Results demonstrated the presence of MAIT cell phenotypes in OLP inflammatory infiltrate within the connective tissue. Significant differences existed between different OLP groups with the percentage of log(CD3+ CD161+) and log(CD3+ TCRVα7.2+) positive cells (p < 0.001 and p = 0.005 respectively). Significant differences also existed with the relative abundance of triple-stained log(CD3+ CD161+ IL18R1+) cells (p = 0.004). A reduction in log(CD3+ CD161+ IL18R1+) cells was observed in lesional tissue of patients with symptomatic OLP with and without Candida when compared to controls. When present in OLP, MAIT cells were identified within the connective tissue. This study demonstrates that mIHC can be used to identify MAIT cell phenotypes in OLP. Reduced percentage of log(CD3+ CD161+ IL18R1+) cells seen in symptomatic OLP with and without Candida suggests a role for these cells in OLP pathogenesis.

The redirected killing of PD-L1 positive tumor cells by the expanded mucosa-associated invariant T (MAIT) cells is mediated with a bispecific antibody targeting TCR Vα7.2 and PD-L1

Pan-T cell targeting by CD3-based T cell engagers has brought program-shift treatment and management of blood tumors. However, these modalities have been shown to provoke all types of T cells leading to cytokine storm syndrome, and activate Treg cells. Thus, modulating and potentiating the antitumor responses of a specific T cell subset was encouraged. We initially found that high purity of mucosa-associated invariant T (MAIT) cells could be expanded by the combination of plate-immobilized Vα7.2 mAb (Clone 3C10) and IL2 plus IL15. Then, we generated a novel anti-Vα7.2 TCR bsAb, Vα7.2 x PD-L1, to invoke the anti-tumor potency of these expanded MAIT cells. Furthermore, our data have demonstrated that Vα7.2 x PD-L1 could mediate the cell-to-cell conjunction between MAIT cell and tumor cell line, selectively elicit the activation, cytokine production, degranulation, and cytotoxicity of the expanded MAIT cells in the presence of target cell only. Collectively, this proof-of-concept study provides a new tool to explore the clinical potential of MAIT cells in fighting against PD-L1 positive solid tumors and suggests additional encouragement in designing novel T cell engagers targeting TCR alpha chain specific innate-like T cells subsets, other than pan CD3+ T cells.

Regulatory mucosa-associated invariant T cells controlled by β1 adrenergic receptor signaling contribute to hepatocellular carcinoma progression.

The innate-like mucosa-associated invariant T (MAIT) cells are enriched in human liver and have been linked to human HCC. However, their contributions to the progression of HCC are controversial due to the heterogeneity of MAIT cells, and new MAIT cell subsets remain to be explored. Combining single cell RNA sequencing (scRNA-seq) and flow cytometry analysis, we performed phenotypic and functional studies and found that FOXP3 + CXCR3 + MAIT cells in HCC patients were regulatory MAIT cells (MAITregs) with high immunosuppressive potential. These MAITregs were induced under Treg-inducing condition and predominantly from FOXP3 - CXCR3 + MAIT cells, which displayed mild Treg-related features and represented a pre-MAITreg reservoir. In addition, the induction and function of MAITregs were promoted by β1 adrenergic receptor signaling in pre-MAITregs and MAITregs, respectively. In HCC patients, high proportion of the intratumoral MAITregs inhibited antitumor immune responses and was associated with poor clinical outcomes. Together, we reveal an immunosuppressive subset of MAIT cells in HCC patients that contributes to HCC progression, and propose a control through neuroimmune crosstalk.

Clinicopathological and predictive value of MAIT cells in non-small cell lung cancer for immunotherapy

BackgroundImmune-checkpoint inhibitors (ICIs) remain ineffective in a large group of non-small cell lung cancer (NSCLC) patients. Mucosal-associated invariant T (MAIT) cells, a population of unconventional innate-like T lymphocytes abundant in...

Role of MR1-driven signals and amphiregulin on the recruitment and repair function of MAIT cells during skin wound healing

Tissue repair processes maintain proper organ function following mechanical or infection-related damage. In addition to antibacterial properties, mucosal associated invariant T (MAIT) cells express a tissue repair transcriptomic program and promote skin wound healing when expanded. Herein, we use a human-like mouse model of full-thickness skin excision to assess the underlying mechanisms of MAIT cell tissue repair function. Single-cell RNA sequencing analysis suggested that skin MAIT cells already express a repair program at steady state. Following skin excision, MAIT cells promoted keratinocyte proliferation, thereby accelerating healing. Using skin grafts, parabiosis, and adoptive transfer experiments, we show that MAIT cells migrated into the wound in a Tcell receptor (TCR)-independent but CXCR6 chemokine receptor-dependent manner. Amphiregulin secreted by MAIT cells following excision promoted wound healing. Expression of the repair function was probably independent of sustained TCR stimulation. Overall, our study provides mechanistic insights into MAIT cell wound healing function in the skin.

Enhancing Mucosal-Associated Invariant T Cell Function and Expansion with Human Selective Serum.

Mucosal-associated invariant T (MAIT) cells are promising innate-like lymphocytes with potential for use in anti-tumor immunotherapy. Existing MAIT cell expansion protocols are associated with potentially decremental phenotypic changes, including increased frequency of CD4+ MAIT cells and higher inhibitory receptor expression. In this study, we compared the effect on expansion of human MAIT cells of a serum replacement, Physiologix XF SR (Phx), with traditional serum FBS for supplementing RPMI 1640 media. Using flow cytometry, we found that Phx supported a significantly higher proliferative capacity for MAIT cells and resulted in a lower frequency of CD4+ MAIT cells, which have been associated with reduced Th1 effector and cytolytic functions. We saw that culturing MAIT cells in Phx led to better survival of MAIT cells and lower frequency of PD-1+ MAIT cells than FBS-supplemented media. Functionally, we saw that Phx supplementation was associated with a higher frequency of IFN-γ+ MAIT cells after stimulation with Escherichia coli than FBS-supplemented RPMI. In conclusion, we show that MAIT cells cultured in Phx have higher proliferative capacity, lower expression of inhibitory receptors, and higher capacity to produce IFN-γ after E. coli stimulation than FBS-supplemented RPMI. This work shows that expanding MAIT cells with Phx compared with FBS-supplemented RPMI results in a more functionally desirable MAIT cell for future anti-tumor immunotherapy.