MR1-restricted Mucosal-associated Invariant T Research Articles

Characterization of the TCRβ repertoire of peripheral MR1-restricted MAIT cells in psoriasis vulgaris patients

Psoriasis vulgaris (PV) is an inflammatory skin disease largely driven by aberrant αβT cells. Mucosal-associated invariant T (MAIT) cells, which constitute the largest circulating innate-like αβT cell community in human adults, are characterized by a semi-invariant TCRVα7.2 receptor and MR1-restricted affinity toward microbial metabolites. Limited MAIT TCRα diversity is complemented by a more variable TCRβ repertoire, but its footprint in the MAIT repertoire of PV patients has never been tested. Here, we used bulk TCRSeq, MiXCR, VDJTools, and Immunarch pipelines to decipher and compare TCRβ clonotypes from flow-sorted, peripheral TCRVα7.2+MR1-5-OP-RU-tet+MAIT cells from 10 PV patients and 10 healthy, matched controls. The resulting TCRβ collections were highly private and individually unique, with small public clonotype content and high CDR3β amino acid length variability in both groups. The age-related increase in the ‘hyperexpanded’ clonotype compartment was observed in PV, but not in healthy MAIT repertoires. The TCRβ repertoires of PV patients were also marked by skewed TRBV/TRBJ pairing, and the emergence of PV-specific, public CDR3β peptide sequences closely matching the published CDR3β record from psoriatic skin. Overall, our study provides preliminary insight into the peripheral MAIT TCRβ repertoire in psoriasis and warrants further evaluation of its diagnostic and clinical significance.

MAIT cells regulate NK cell-mediated tumor immunity

The function of MR1-restricted mucosal-associated invariant T (MAIT) cells in tumor immunity is unclear. Here we show that MAIT cell-deficient mice have enhanced NK cell-dependent control of metastatic B16F10 tumor growth relative to control mice. Analyses of this interplay in human tumor samples reveal that high expression of a MAIT cell gene signature negatively impacts the prognostic significance of NK cells. Paradoxically, pre-pulsing tumors with MAIT cell antigens, or activating MAIT cells in vivo, enhances anti-tumor immunity in B16F10 and E0771 mouse tumor models, including in the context of established metastasis. These effects are associated with enhanced NK cell responses and increased expression of both IFN-γ-dependent and inflammatory genes in NK cells. Importantly, activated human MAIT cells also promote the function of NK cells isolated from patient tumor samples. Our results thus describe an activation-dependent, MAIT cell-mediated regulation of NK cells, and suggest a potential therapeutic avenue for cancer treatment.

MR1-Restricted MAIT Cells From The Human Lung Mucosal Surface Have Distinct Phenotypic, Functional, and Transcriptomic Features That Are Preserved in HIV Infection.

Mucosal associated invariant T (MAIT) cells are a class of innate-like T cells that utilize a semi-invariant αβ T cell receptor to recognize small molecule ligands produced by bacteria and fungi. Despite growing evidence that immune cells at mucosal surfaces are often phenotypically and functionally distinct from those in the peripheral circulation, knowledge about the characteristics of MAIT cells at the lung mucosal surface, the site of exposure to respiratory pathogens, is limited. HIV infection has been shown to have a profound effect on the number and function of MAIT cells in the peripheral blood, but its effect on lung mucosal MAIT cells is unknown. We examined the phenotypic, functional, and transcriptomic features of major histocompatibility complex (MHC) class I-related (MR1)-restricted MAIT cells from the peripheral blood and bronchoalveolar compartments of otherwise healthy individuals with latent Mycobacterium tuberculosis (Mtb) infection who were either HIV uninfected or HIV infected. Peripheral blood MAIT cells consistently co-expressed typical MAIT cell surface markers CD161 and CD26 in HIV-negative individuals, while paired bronchoalveolar MAIT cells displayed heterogenous expression of these markers. Bronchoalveolar MAIT cells produced lower levels of pro-inflammatory cytokine IFN-γ and expressed higher levels of co-inhibitory markers PD-1 and TIM-3 than peripheral MAIT cells. HIV infection resulted in decreased frequencies and pro-inflammatory function of peripheral blood MAIT cells, while in the bronchoalveolar compartment MAIT cell frequency was decreased but phenotype and function were not significantly altered. Single-cell transcriptomic analysis demonstrated greater heterogeneity among bronchoalveolar compared to peripheral blood MAIT cells and suggested a distinct subset in the bronchoalveolar compartment. The transcriptional features of this bronchoalveolar subset were associated with MAIT cell tissue repair functions. In summary, we found previously undescribed phenotypic and transcriptional heterogeneity of bronchoalveolar MAIT cells in HIV-negative people. In HIV infection, we found numeric depletion of MAIT cells in both anatomical compartments but preservation of the novel phenotypic and transcriptional features of bronchoalveolar MAIT cells.

Immune Monitoring of Human Mucosal-Associated Invariant T Cells by Quantitative Proteomics.

Molecular phenotypes of mucosal-associated invariant T (MAIT) cells are correlating with individual susceptibilities and outcomes in human diseases. Quantitative proteome strategies can examine such variations in the functional and druggable inventory of MAIT cells comprehensively, but protocols for the support of translational and clinical studies are still rare. Here, we describe a protocol in which MR1-restricted MAIT cells were isolated from blood donations by FACS and are then characterized by quantitative proteomics (iTRAQ-LC-MS/MS) to complement information about their unique effector phenotype and to investigate donor-/patient- or disease-specific variations in protein networks with high precision.

Elevated frequencies of total and MAIT cell subsets in patients with knee osteoarthritis.

BackgroundOsteoarthritis (OA) is characterized by the degeneration of joint cartilage, with concomitant changes in the synovium and subchondral bone. Recently, the inflammatory response and involvement of several types of T-cells has been implicated in the development of OA. This study investigated the frequency of MR1-restricted mucosal-associated invariant T (MAIT) cells in patients with knee OA.MethodsForty-five patients recently diagnosed with knee OA and 21 age- and gender-matched healthy controls were recruited for this study. Percentages of circulating MAIT cells were assessed by flow cytometry. Plasma cytokine levels were measured using cytometric bead arrays. Associations between the percentages of MAIT cells, plasma cytokine levels, and clinical parameters of OA (erythrocyte sedimentation rate [ESR] and the Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) were analyzed using the Spearman correlation test.ResultsThe percentages of total, CD8αα, and CD8αβ MAIT cells were higher in patients with OA compared to healthy controls. The percentages of total and CD8αα MAIT cells were higher in patients with multi-joint OA (MOA) compared to patients with knee-only OA (KOA). Plasma IFN-γ and TNF-α levels were elevated in patients with OA compared to healthy controls, and there was a positive correlation between plasma IFN-γ levels and the percentages of total, CD8αα, and CD8αβ MAIT cells. Plasma IFN-γ and IL-17 levels were higher in patients with MOA compared to healthy controls or patients with KOA. There were positive correlations between the percentages of total and CD8αα MAIT cells and clinical parameters (ESR and WOMAC scores) in patients with OA or MOA. Binary logistic regression analysis shown the frequency of MAIT cells was associated with the risk of OA.ConclusionsMAIT cells and their subpopulations were significantly increased in patients with OA and have potential as biological markers of OA disease severity, especially in patients with MOA.

Mucosal-associated invariant T cells and oral microbiome in persistent apical periodontitis

Opportunistic bacteria in apical periodontitis (AP) may pose a risk for systemic dissemination. Mucosal-associated invariant T (MAIT) cells are innate-like T cells with a broad and potent antimicrobial activity important for gut mucosal integrity. It was recently shown that MAIT cells are present in the oral mucosal tissue, but the involvement of MAIT cells in AP is unknown. Here, comparison of surgically resected AP and gingival tissues demonstrated that AP tissues express significantly higher levels of Vα7.2-Jα33, Vα7.2-Jα20, Vα7.2-Jα12, Cα and tumour necrosis factor (TNF), interferon (IFN)-γ and interleukin (IL)-17A transcripts, resembling a MAIT cell signature. Moreover, in AP tissues the MR1-restricted MAIT cells positive for MR1–5-OP-RU tetramer staining appeared to be of similar levels as in peripheral blood but consisted mainly of CD4+ subset. Unlike gingival tissues, the AP microbiome was quantitatively impacted by factors like fistula and high patient age and had a prominent riboflavin-expressing bacterial feature. When merged in an integrated view, the examined immune and microbiome data in the sparse partial least squares discriminant analysis could identify bacterial relative abundances that negatively correlated with Vα7.2-Jα33, Cα, and IL-17A transcript expressions in AP, implying that MAIT cells could play a role in the local defence at the oral tissue barrier. In conclusion, we describe the presence of MAIT cells at the oral site where translocation of oral microbiota could take place. These findings have implications for understanding the immune sensing of polymicrobial-related oral diseases.

A comparative analysis of mucosal associated invariant T cells and invariant natural killer T cells

Event Abstract Back to Event A comparative analysis of mucosal associated invariant T cells and invariant natural killer T cells Zarina T. Zainudeen1, 2*, Aman S. Abdul Majid3 and Chris Willberg1, 4 1 University of Oxford, Nuffield Department of Clinical Neurosciences, United Kingdom 2 Advanced Medical and Dental Institute, University of Science, Malaysia, Cluster of Regenerative Medicine, Malaysia 3 Quest International University Perak, Department of Pharmacology, Faculty of Medicine, Malaysia 4 University of Oxford, Experimental Medicine Division, United Kingdom Background CD1d-restricted invariant natural killer T (iNKT) cells and MR-1-restricted mucosal associated invariant T (MAIT) cells are two subsets of non-conventional T cells, with conserved T-cell receptor (TCR) repertoire, functions, homing and cytokine production. Both cell types show remarkable differences in their abundance in humans and mice; iNKT cells are found at a higher frequency in mice than human, whereas the opposite situation is true for MAIT cells. This suggests that the T cell subsets can potentially replace the other. Since MAIT cells dominate CD161++CD8+T cell population, the aim of this study is to compare the common phenotypes and roles between CD161++CD8+ T and iNKT cells. Methods CD161++CD8+ T and iNKT cells were characterised in terms of chemokine and cytokine receptor expression and functionality. This study compared peripheral blood iNKT cells and MAIT cells from healthy individuals. Since CD161 is widely expressed by lymphocytes, flow cytometry was employed to analyse the two study populations at the single cell level, and distinguish them from other CD161 expressing cells. Results Both cell types displayed preferential tissue-homing molecules, and different subsets of CD4/CD8 cell. Some of the Th17 characteristics were also found in iNKT cells, like IL23R and CCR6. In the present study, both the cells expressed granzyme A, K and perforin, with lower/undetectable expression of granzyme B. CD161++CD8+T cells were also observed to express higher levels of D prostanoid receptor (DP) 1 at the cell surface and at the mRNA level when compared to those seen in iNKT cells. Conclusions CD161++CD8+ T and iNKT cells are distinctive from conventional T cells. Both these cells are selectively recruited to the site of inflammation and exhibit antimicrobial activity. Although some overlapping functions were observed between these populations, differences were detected in the cytokine expressions and cytolytic granule contents. Acknowledgements We thank Prof Paul Klenerman and his research group for their guidance. Research is partly funded by Dr Chris Willberg's grant. Keywords: CD161++CD8+ T cells, iNKT cells, IL23R, CCR6, DP1 Conference: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”, Putrajaya, Malaysia, 3 Dec - 5 Feb, 2019. Presentation Type: Oral Presentation Topic: Inflammatory diseases Citation: Zainudeen ZT, Abdul Majid AS and Willberg C (2019). A comparative analysis of mucosal associated invariant T cells and invariant natural killer T cells. Front. Pharmacol. Conference Abstract: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”. doi: 10.3389/conf.fphar.2018.63.00019 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Nov 2018; Published Online: 17 Jan 2019. * Correspondence: PhD. Zarina T Zainudeen, University of Oxford, Nuffield Department of Clinical Neurosciences, Oxford, England, OX1 2JD, United Kingdom, zarinazainudeen@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Zarina T Zainudeen Aman S Abdul Majid Chris Willberg Google Zarina T Zainudeen Aman S Abdul Majid Chris Willberg Google Scholar Zarina T Zainudeen Aman S Abdul Majid Chris Willberg PubMed Zarina T Zainudeen Aman S Abdul Majid Chris Willberg Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

MR1-restricted mucosal-associated invariant T (MAIT) cells respond to mycobacterial vaccination and infection in nonhuman primates

Studies on mucosal-associated invariant T cells (MAITs) in nonhuman primates (NHP), a physiologically relevant model of human immunity, are handicapped due to a lack of macaque MAIT-specific reagents. Here we show that while MR1 ligand-contact residues are conserved between human and multiple NHP species, three T-cell receptor contact-residue mutations in NHP MR1 diminish binding of human MR1 tetramers to macaque MAITs. Construction of naturally loaded macaque MR1 tetramers facilitated identification and characterization of macaque MR1-binding ligands and MAITs, both of which mirrored their human counterparts. Using the macaque MR1 tetramer we show that NHP MAITs activated in vivo in response to both Bacillus Calmette-Guerin vaccination and Mycobacterium tuberculosis infection. These results demonstrate that NHP and human MR1 and MAITs function analogously, and establish a preclinical animal model to test MAIT-targeted vaccines and therapeutics for human infectious and autoimmune disease.

MR1-Restricted Mucosal-Associated Invariant T Cells and Their Activation during Infectious Diseases

MR1-restricted mucosal-associated invariant T (MAIT) cells recognize vitamin B metabolites, which are generated by a broad range of bacteria, from Escherichia coli to Mycobacterium tuberculosis and BCG. MAIT cells have been described as innate sensors of infection as they accumulate early in infected tissues. MAIT cells maintain an activated phenotype throughout the course of infections, secrete inflammatory cytokines, and have the potential to directly kill infected cells, playing an important role in shaping the host response. In this review, we will discuss the current knowledge regarding the molecular mechanisms that underline MAIT cells activation in sterile and non-sterile inflammatory conditions.

MR1-restricted MAIT cells display ligand discrimination and pathogen selectivity through distinct T cell receptor usage.

Mucosal-associated invariant T (MAIT) cells express a semi-invariant T cell receptor (TCR) that detects microbial metabolites presented by the nonpolymorphic major histocompatibility complex (MHC)-like molecule MR1. The highly conserved nature of MR1 in conjunction with biased MAIT TCRα chain usage is widely thought to indicate limited ligand presentation and discrimination within a pattern-like recognition system. Here, we evaluated the TCR repertoire of MAIT cells responsive to three classes of microbes. Substantial diversity and heterogeneity were apparent across the functional MAIT cell repertoire as a whole, especially for TCRβ chain sequences. Moreover, different pathogen-specific responses were characterized by distinct TCR usage, both between and within individuals, suggesting that MAIT cell adaptation was a direct consequence of exposure to various exogenous MR1-restricted epitopes. In line with this interpretation, MAIT cell clones with distinct TCRs responded differentially to a riboflavin metabolite. These results suggest that MAIT cells can discriminate between pathogen-derived ligands in a clonotype-dependent manner, providing a basis for adaptive memory via recruitment of specific repertoires shaped by microbial exposure.

Co-dependents: MR1-restricted MAIT cells and their antimicrobial function

Mucosal-associated invariant T (MAIT) cells are a unique T cell subset in mammals. They are present at high frequencies at mucosal tissue sites and have an intrinsic capacity to respond to microbial infections. The semi-invariant antigen recognition receptor of MAIT cells detects the non-polymorphic antigen-presenting molecule major histocompatibility complex class I-related protein 1 (MR1), which can bind microorganism-derived riboflavin metabolites. The striking evolutionary conservation in both the MR1 molecule and the MAIT T cell receptor suggests that strong selective pressures maintain this T cell pattern recognition system which detects microbial infection.

Human thymic MR1-restricted MAIT cells are innate pathogen-reactive effectors that adapt following thymic egress.

Human mucosal-associated invariant T (MAIT) cells express the semi-invariant T cell receptor Vα7.2 and are restricted by the MHC-Ib molecule MR1. While MAIT cells share similarities with other innate T cells the extent to which MAIT cells are innate and their capacity to adapt is unknown. We evaluated the function of Vα7.2+ T cells from the thymus, cord blood, and peripheral blood. While antigen-inexperienced MAIT cells displayed a naive phenotype these had intrinsic effector capacity in response to Mycobacterium tuberculosis infected cells. Vα7.2+ effector thymocytes contained sjTREC suggesting limited replication and thymic origin. In evaluating the capacity of Mtb-reactive MAIT cells to adapt, we found that those from peripheral blood demonstrated a memory phenotype and had undergone substantial expansion suggesting they responded to antigenic stimulation. MAIT cells, an evolutionarily conserved T cell subset that detects a variety of intracellular infections, share features of innate and adaptive immunity.