Transcriptome of activated human and mouse MAIT cells
ABSTRACT: We sought to describe in detail the consequences of MAIT cell activation using a transcriptomic approach to define the basic transcriptome of a MAIT cell in both humans and mice and to determine how this is modulated by activation. Fresh human peripheral blood cells were obtained from three donors. These were cultured for 6 hours with (‘stimulated’) or without (‘unstimulated’) 10 nM 5-OP-RU, magnetically enriched on MR1-tetramer+ cells, and flow-sorted for RNA sequencing of live CD3+TCR Valpha7.2+ MR1-5-OP-RU tetramer+ MAIT cells, and of unstimulated naïve live CD8+CD45RA+ T cells as a comparator cell type. For the murine samples we included within the same sequencing experiment live pulmonary CD3+45.2+19-MR1-5-OP-RU tetramer+ MAIT cells which were magnetically enriched and flow-sorted from the lungs of mice 7 days after infection with 1x104 CFU L. longbeachae (‘acute’), or at least 12 weeks post infection (‘resolution’) or 7 days after a second intranasal infection with 2x104 CFU L. longbeachae in mice that had recovered from infection 12 weeks previously (‘reinfection’). Live CD3+CD45.2+CD19-CD8+CD44-CD62L+ naïve T cells from uninfected mice were used as a comparator cell type. Overall design: Illumina sequencing of human and murine MR1-5-OP-RU tetramer+ MAIT cells in comparison with naïve CD8 T cells. 3 biological replicates of each of the following conditions: Human peripheral blood MAIT cell unstimulated. Human peripheral blood MAIT cells stimulated for 6 h with 5-OP-RU. Human peripheral blood CD8+45RA+ T cells. Murine pulmonary MAIT cells 7 days after legionella infection, 12 weeks after legionella infection, 7 days after reinfection with legionella, Murine naive pulmonary CD8+CD45+44-62L+ T cells. Full details of the study can be downloaded at https://www.biorxiv.org/content/early/2018/12/09/490649?rss=1
Project description:MR1-restricted T (MR1T) cells are defined by their recognition of metabolite antigens presented by the monomorphic MHC class 1-related molecule, MR1, the most highly conserved MHC class I related molecule in mammalian species. Mucosal-associated invariant T (MAIT) cells are the predominant subset of MR1T cells expressing an invariant TCR ?-chain, TRAV1-2. These cells comprise a T cell subset that recognizes and mediates host immune responses to a broad array of microbial pathogens, including Mycobacterium tuberculosis. Here, we sought to characterize development of circulating human MR1T cells as defined by MR1-5-OP-RU tetramer labeling and of the TRAV1-2+ MAIT cells defined by expression of TRAV1-2 and high expression of CD26 and CD161 (TRAV1-2+CD161++CD26++ cells). We analyzed postnatal expansion, maturation, and functionality of peripheral blood MR1-5-OP-RU tetramer+ MR1T cells in cohorts from three different geographic settings with different tuberculosis (TB) vaccination practices, levels of exposure to and infection with M. tuberculosis. Early after birth, frequencies of MR1-5-OP-RU tetramer+ MR1T cells increased rapidly by several fold. This coincided with the transition from a predominantly CD4+ and TRAV1-2- population in neonates, to a predominantly TRAV1-2+CD161++CD26++ CD8+ population. We also observed that tetramer+ MR1T cells that expressed TNF upon mycobacterial stimulation were very low in neonates, but increased ~10-fold in the first year of life. These functional MR1T cells in all age groups were MR1-5-OP-RU tetramer+TRAV1-2+ and highly expressed CD161 and CD26, markers that appeared to signal phenotypic and functional maturation of this cell subset. This age-associated maturation was also marked by the loss of naïve T cell markers on tetramer+ TRAV1-2+ MR1T cells more rapidly than tetramer+TRAV1-2- MR1T cells and non-MR1T cells. These data suggest that neonates have infrequent populations of MR1T cells with diverse phenotypic attributes; and that exposure to the environment rapidly and preferentially expands the MR1-5-OP-RU tetramer+TRAV1-2+ population of MR1T cells, which becomes the predominant population of functional MR1T cells early during childhood.
Project description:Mucosal-Associated Invariant T cells (MAIT cells) have a unique specificity for the microbial metabolite 5-OP-RU presented by the non-classical presentation molecule MR1. Upon activation, they release cytotoxic mediators and engage an antimicrobial activity. As a subset of T lymphocytes, MAIT development occurs in the thymus where they acquire their effector phenotype under the control of the key transcription factor ZBTB16. This particular maturation process is in contrast with conventional T cells that egress the thymus with a naive phenotype before populating the secondary lymphoid organs, and the molecular events driving the MAIT lineage decision are poorly known. In the present work, we evaluated the transcriptional events and the role of the slam-SAP pathway on the lineage decision of MR1-restricted T cells by single cell RNAseq. MAIT cells undergoing positive selection were FACS-sorted with a MR1:5-OP-RU labeled tetramer, from thymus of wild-type and sapKO mice. Their transcriptomes were captured using a 10x chromium system.
Project description:MAIT cells (MAITs) represent an abundant T lymphocyte subset with unique specificity for microbial metabolites presented by the MHC-1b molecule, MR1. MAIT conservation along evolution indicates important, non-redundant functions, but their low frequency in mice has hampered their detailed characterization. Here, we performed a transcriptomic analysis of murine MAITs in comparison with NKT subsets and with mainstream T cells in spleen and peripheral organs of B6-MAIT/CAST mice expressing a Rorc-GFP transgene. MAIT and NKT cells have been FACS-sorted after tetramer staining (MR1:5-OP-RU Tet+ for MAIT, CD1d:PBS57Tet+ for NKT), and 1/17 subsetting based on the expression of Rorc.
Project description:Mucosal-associated invariant T (MAIT) cells are semi-invariant V?7.2+ CD161highCD4- T cells that recognize microbial riboflavin precursor derivatives such as 5-OP-RU presented by MR1. Human MAIT cells are abundant in adult blood, but there are very few in cord blood. We longitudinally studied V?7.2+ CD161high T cell and related subset levels in infancy and after cord blood transplantation. We show that V?7.2+ and V?7.2- CD161high T cells are generated early during gestation and likely share a common prenatal developmental program. Among cord blood V?7.2+ CD161high T cells, the minority recognizing MR1:5-OP-RU display a TRAV/TRBV repertoire very similar to adult MAIT cells. Within a few weeks of life, only the MR1:5-OP-RU reactive V?7.2+ CD161high T cells acquire a memory phenotype. Only these cells expand to form the adult MAIT pool, diluting out other V?7.2+ CD161high and V?7.2- CD161high populations, in a process requiring at least 6 years to reach adult levels. Thus, the high clonal size of adult MAIT cells is antigen-driven and likely due to the fine specificity of the TCR?? chains recognizing MR1-restricted microbial antigens.
Project description:Mucosal-associated invariant T (MAIT) cells have a semi-invariant TCR V?-chain, and their optimal development is dependent upon commensal flora and expression of the nonpolymorphic MHC class I-like molecule MR1. MAIT cells are activated in an MR1-restricted manner by diverse strains of bacteria and yeast, suggesting a widely shared Ag. Recently, human and mouse MR1 were found to bind bacterial riboflavin metabolites (ribityllumazine [RL] Ags) capable of activating MAIT cells. In this study, we used MR1/RL tetramers to study MR1 dependency, subset heterogeneity, and protective effector functions important for tuberculosis immunity. Although tetramer(+) cells were detected in both MR1(+/+) and MR1(-/-) TCR V?19i-transgenic (Tg) mice, MR1 expression resulted in significantly increased tetramer(+) cells coexpressing TCR V?6/8, NK1.1, CD44, and CD69 that displayed more robust in vitro responses to IL-12 plus IL-18 and RL Ag, indicating that MR1 is necessary for the optimal development of the classic murine MAIT cell memory/effector subset. In addition, tetramer(+) MAIT cells expressing CD4, CD8, or neither developing in MR1(+/+) V?19i-Tg mice had disparate cytokine profiles in response to RL Ag. Therefore, murine MAIT cells are considerably more heterogeneous than previously thought. Most notably, after mycobacterial pulmonary infection, heterogeneous subsets of tetramer(+) V?19i-Tg MAIT cells expressing CXCR3 and ?4?1 were recruited into the lungs and afforded early protection. In addition, V?19iC?(-/-)MR(+/+) mice were significantly better protected than were V?19iC?(-/-)MR1(-/-), wild-type, and MR1(-/-) non-Tg mice. Overall, we demonstrate considerable functional diversity of MAIT cell responses, as well as that MR1-restricted MAIT cells are important for tuberculosis protective immunity.
Project description:Mucosal-associated invariant T cells (MAIT cells) express a semi-invariant T cell receptor (TCR) ?-chain, TRAV1-2-TRAJ33, and are activated by vitamin B metabolites bound by the major histocompatibility complex (MHC)-related class I-like molecule, MR1. Understanding MAIT cell biology has been restrained by the lack of reagents to specifically identify and characterize these cells. Furthermore, the use of surrogate markers may misrepresent the MAIT cell population. We show that modified human MR1 tetramers loaded with the potent MAIT cell ligand, reduced 6-hydroxymethyl-8-D-ribityllumazine (rRL-6-CH?OH), specifically detect all human MAIT cells. Tetramer(+) MAIT subsets were predominantly CD8(+) or CD4(-)CD8(-), although a small subset of CD4(+) MAIT cells was also detected. Notably, most human CD8(+) MAIT cells were CD8?(+)CD8?(-/lo), implying predominant expression of CD8?? homodimers. Tetramer-sorted MAIT cells displayed a T(H)1 cytokine phenotype upon antigen-specific activation. Similarly, mouse MR1-rRL-6-CH?OH tetramers detected CD4(+), CD4(-)CD8(-) and CD8(+) MAIT cells in V?19 transgenic mice. Both human and mouse MAIT cells expressed a broad TCR-? repertoire, and although the majority of human MAIT cells expressed TRAV1-2-TRAJ33, some expressed TRAJ12 or TRAJ20 genes in conjunction with TRAV1-2. Accordingly, MR1 tetramers allow precise phenotypic characterization of human and mouse MAIT cells and revealed unanticipated TCR heterogeneity in this population.
Project description: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.
Project description:The antigen-presenting molecule MR1 presents riboflavin-based metabolites to Mucosal-Associated Invariant T (MAIT) cells. While MR1 egress to the cell surface is ligand-dependent, the ability of small-molecule ligands to impact on MR1 cellular trafficking remains unknown. Arising from an in silico screen of the MR1 ligand-binding pocket, we identify one ligand, 3-([2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-yl]formamido)propanoic acid, DB28, as well as an analog, methyl 3-([2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-yl]formamido)propanoate, NV18.1, that down-regulate MR1 from the cell surface and retain MR1 molecules in the endoplasmic reticulum (ER) in an immature form. DB28 and NV18.1 compete with the known MR1 ligands, 5-OP-RU and acetyl-6-FP, for MR1 binding and inhibit MR1-dependent MAIT cell activation. Crystal structures of the MAIT T cell receptor (TCR) complexed with MR1-DB28 and MR1-NV18.1, show that these two ligands reside within the A'-pocket of MR1. Neither ligand forms a Schiff base with MR1 molecules; both are nevertheless sequestered by a network of hydrophobic and polar contacts. Accordingly, we define a class of compounds that inhibits MR1 cellular trafficking.
Project description:Mucosal associated invariant T (MAIT) cells recognise conserved microbial metabolites from riboflavin synthesis. Striking evolutionary conservation and pulmonary abundance implicate them in antibacterial host defence, yet their functions in protection against clinically important pathogens are unknown. Here we show that mouse Legionella longbeachae infection induces MR1-dependent MAIT cell activation and rapid pulmonary accumulation of MAIT cells associated with immune protection detectable in immunocompetent host animals. MAIT cell protection is more evident in mice lacking CD4+ cells, and adoptive transfer of MAIT cells rescues immunodeficient Rag2-/-?C-/- mice from lethal Legionella infection. Protection is dependent on MR1, IFN-? and GM-CSF, but not IL-17A, TNF or perforin, and enhanced protection is detected earlier after infection of mice antigen-primed to boost MAIT cell numbers before infection. Our findings define a function for MAIT cells in protection against a major human pathogen and indicate a potential role for vaccination to enhance MAIT cell immunity.
Project description:Psoriasis vulgaris (PV) is a chronic, recurrent inflammatory dermatosis mediated by aberrantly activated immune cells. The role of the innate-like T cells, particularly gammadelta T (??T) cells and MR1-restricted T lymphocytes, is incompletely explored, mainly through animal models, or by use of surrogate lineage markers, respectively. Here, we used case-control settings, multiparameter flow cytometry, 5-OP-RU-loaded MR1-tetramers, Luminex technology and targeted qRT-PCR to dissect the cellular and transcriptional landscape of ?? and MR1-restricted blood T cells in untreated PV cases (n=21, 22 matched controls). High interpersonal differences in cell composition were observed, fueling transcriptional variability at healthy baseline. A minor subset of canonical CD4<sup>+</sup>CD8<sup>+</sup>MR1-tet<sup>+</sup>TCRV?7.2<sup>+</sup> and CD4<sup>+</sup>CD8<sup>-</sup>MR1-tet<sup>+</sup>TCRV?7.2<sup>+</sup> T cells was the most significantly underrepresented community in male PV individuals, whereas V?2<sup>+</sup> ?? T cells expressing high levels of TCR and V?1<sup>-</sup>?2<sup>-</sup> ?? T cells expressing intermediate levels of TCR were selectively enriched in affected males, partly reflecting disease severity. Our findings highlight a formerly unappreciated skewing of human circulating MAIT and ?? cytomes during PV, and reveal their compositional changes in relation to sex, CMV exposure, serum cytokine content, BMI, and inflammatory burden. Complementing numerical alterations, we finally show that flow-sorted, MAIT and ?? populations exhibit divergent transcriptional changes in mild type I psoriasis, consisting of differential bulk expression for signatures of cytotoxicity/type-1 immunity (<i>EOMES, RUNX3, IL18R</i>), type-3 immunity (<i>RORC</i>, <i>CCR6</i>), and T cell innateness (<i>ZBTB16</i>).