Peripheral Mucosal-associated Invariant T Cells Research Articles

Enrichment of liver MAIT cells in a mouse model of Alzheimer's disease

Emerging evidence has supported a role for the immune system and liver in Alzheimer's disease (AD). However, our understanding of how hepatic immune cells are altered in AD is limited. We previously found that brain mucosal-associated invariant T (MAIT) cell numbers are increased in AD. Furthermore, loss of MAIT cells and their antigen-presenting molecule, MR1, reduced amyloid-β accumulation in the brain. MAIT cells are also significantly present in the liver. Therefore, we sought to analyze MAIT and other immune cells in the AD liver. Increased frequency of activated MAIT cells (but not conventional T cells) were found in 8-month-old 5XFAD mouse livers. Therefore, these data raise the possibility that there is a role for peripheral MAIT cells in AD pathology.

Expansion of MAIT cells in the combined absence of NKT and γδ-T cells

Mucosal-associated invariant T (MAIT) cells, natural killer T (NKT) cells, and γδT cells are collectively referred to as 'unconventional T cells' due to their recognition of non-peptide antigens and restriction to non-classical MHC-I-like molecules. Though the frequencies of MAIT, NKT and γδT cells and distribution of their functional subsets vary widely between organs and individuals, the factors controlling these differences are poorly understood. Here, we show that MAIT cells are increased in mice deficient in either NKT or γδT cells and even more-so in mice deficient in both NKT and γδT cells. In addition, characterisation of the TCRα repertoire within γδT cell-deficient thymocytes revealed an altered Trav gene segment usage relative to that of WT thymocytes, highlighting a retention of the Tcra-Tcrd locus from 129 strain embryonic stem cells used to generate Tcrd-/- mice. Accordingly, this resulted in a moderate increase in distal Trav segment usage such as Trav1, potentially contributing to increased generation of Trav1-Traj33+ MAIT cells in the Tcrd-/- thymus. However, peripheral MAIT cells also underwent increased homeostatic proliferation in the absence of NKT and γδT cells and adoptively transferred MAIT cell subsets exhibited tissue-specific homing patterns. Collectively, our data reveals a shared niche for MAIT, NKT, and γδT cells, suggesting a competition for common factors that could be exploited for treating disease. Importantly, these data highlight that careful assessment of studies using NKT or γδT cell-deficient mouse models is required when investigating the role of unconventional T cells in disease.

Dysregulation of circulating MAIT cell subsets in patients with hidradenitis suppurativa

Abstract Hidradenitis suppurativa (HS) is a chronic inflammatory condition characterized by painful and debilitating skin lesions. Recent reports purport HS as an autoinflammatory keratinization disease with numerous pathways and features of systemic inflammation however few studies have been conducting to characterize peripheral immune dysregulation. Mucosal associated invariant T (MAIT) cells are an invariant T cell subset responding directly to bacterial threats and their dysregulation contributes to the pathogenesis of autoimmune disorders, cancers and inflammatory skin conditions. Here, we analyzed MAIT cells in the blood of 16 HS patients and 12 healthy controls (HC) by flow cytometry. We found that the frequency of MAIT cells did not change in HS patients, but their function changed drastically. We observed a significant reduction in the frequency of IFNy+ and TNFα+ MAIT cells in the periphery of HS patients. Furthermore, we analyzed MAIT cell subsets by their CD4 surface expression. Here, we found that the frequency of CD4+MAIT cells in the periphery of HS patients is significantly increased, while the frequency of CD4-MAIT cells is significantly decreased. Furthermore, HS patients have a reduction in CD4− IFNg+ and TNFa+ MAIT cells. Overall, these findings suggest that peripheral MAIT cells are dysregulated in HS patients which may contribute to the pathogenesis of the disease. NIH/NIAMS (1R21AR079089 and 1R01AR078688) for Dr. Mi and Henry Ford Immunology Program grant (T71017 for Dr. Mi and T71016 for Di Zhou).

Mucosal-Associated Invariant T (MAIT) cells are highly activated in duodenal tissue of humans with Vibrio cholerae O1 infection: A preliminary report.

Mucosal-associated invariant T (MAIT) cells are unconventional T lymphocytes with a semi-conserved TCRα, activated by the presentation of vitamin B metabolites by the MHC-I related protein, MR1, and with diverse innate and adaptive effector functions. The role of MAIT cells in acute intestinal infections, especially at the mucosal level, is not well known. Here, we analyzed the presence and phenotype of MAIT cells in duodenal biopsies and paired peripheral blood samples, in patients during and after culture-confirmed Vibrio cholerae O1 infection. Immunohistochemical staining of duodenal biopsies from cholera patients (n = 5, median age 32 years, range 26-44, 1 female) identified MAIT cells in the lamina propria of the crypts, but not the villi. By flow cytometry (n = 10, median age 31 years, range 23-36, 1 female), we showed that duodenal MAIT cells are more activated than peripheral MAIT cells (p < 0.01 across time points), although there were no significant differences between duodenal MAIT cells at day 2 and day 30. We found fecal markers of intestinal permeability and inflammation to be correlated with the loss of duodenal (but not peripheral) MAIT cells, and single-cell sequencing revealed differing T cell receptor usage between the duodenal and peripheral blood MAIT cells. In this preliminary report limited by a small sample size, we show that MAIT cells are present in the lamina propria of the duodenum during V. cholerae infection, and more activated than those in the blood. Future work into the trafficking and tissue-resident function of MAIT cells is warranted.

Multiomic analysis reveals decidual-specific transcriptional programing of MAIT cells.

Mucosal-Associated Invariant T (MAIT) cells have been recently identified at the maternal-fetal interface. However, transcriptional programming of decidual MAIT cells in pregnancy remains poorly understood. We employed a multiomic approach to address this question. Mononuclear cells from the decidua basalis and parietalis, and control PBMCs, were analyzed via flow cytometry to investigate MAIT cells in the decidua and assess their transcription factor expression. In a separate study, both decidual and matched peripheral MAIT cells were analyzed using Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq) coupled with gene expression analysis. Lastly, decidual MAIT cells were stimulated with E.coli and expression of MR1 by antigen presenting cells was measured to evaluate decidual MAIT cell function. First, we identified MAIT cells in both the decidua basalis and parietalis. CITE-seq, coupled with scRNA-seq gene expression analysis, highlighted transcriptional programming differences between decidual and matched peripheral MAIT cells at a single cell resolution. Transcription factor expression analysis further highlighted transcriptional differences between decidual MAIT cells and non-matched peripheral MAIT cells. Functionally, MAIT cells are skewed towards IFNγ and TNFα production upon stimulation, with E.coli leading to IFNγ production. Lastly, we demonstrate that MR1, the antigen presenting molecule restricting MAIT cells, is expressed by decidual APCs. MAIT cells are present in the decidua basalis and obtain a unique gene expression profile. The presence of MR1 on APCs coupled with in vitro activation by E.coli suggests that MAIT cells might be involved in tissue-repair mechanisms at the maternal-fetal interface.

Suppressive Monocytes Impair MAIT Cells Response via IL-10 in Patients with Severe COVID-19.

Immune cell responses are strikingly altered in patients with severe coronavirus disease 2019 (COVID-19), but the immunoregulatory process in these individuals is not fully understood. In this study, 23 patients with mild and 22 patients with severe COVID-19 and 6 asymptomatic carriers of COVID-19 were enrolled, along with 44 healthy controls (HC). Peripheral immune cells in HC and patients with COVID-19 were comprehensively profiled using mass cytometry. We found that in patients with severe COVID-19, the number of HLA-DRlow/- monocytes was significantly increased, but that of mucosal-associated invariant T (MAIT) cells was greatly reduced. MAIT cells were highly activated but functionally impaired in response to Escherichia coli and IL-12/IL-18 stimulation in patients with severe COVID-19, especially those with microbial coinfection. Single-cell transcriptome analysis revealed that IFN-stimulated genes were significantly upregulated in peripheral MAIT cells and monocytes from patients with severe COVID-19. IFN-α pretreatment suppressed MAIT cells' response to E. coli by triggering high levels of IL-10 production by HLA-DRlow/--suppressive monocytes. Blocking IFN-α or IL-10 receptors rescued MAIT cell function in patients with severe COVID-19. Moreover, plasma from patients with severe COVID-19 inhibited HLA-DR expression by monocytes through IL-10. These data indicate a unique pattern of immune dysregulation in severe COVID-19, which is characterized by enrichment of suppressive HLA-DRlow/- monocytes associated with functional impairment of MAIT cells through the IFN/IL-10 pathway.

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.

MicroRNA-155 Regulates MAIT1 and MAIT17 Cell Differentiation.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that develop in the thymus through three maturation stages to acquire effector function and differentiate into MAIT1 (T-bet+) and MAIT17 (RORγt+) subsets. Upon activation, MAIT cells release IFN-γ and IL-17, which modulate a broad spectrum of diseases. Recent studies indicate defective MAIT cell development in microRNA deficient mice, however, few individual miRNAs have been identified to regulate MAIT cells. MicroRNA-155 (miR-155) is a key regulator of numerous cellular processes that affect some immune cell development, but its role in MAIT cell development remains unclear. To address whether miR-155 is required for MAIT cell development, we performed gain-of-function and loss-of-function studies. We first generated a CD4Cre.miR-155 knock-in mouse model, in which miR-155 is over-expressed in the T cell lineage. We found that overexpression of miR-155 significantly reduced numbers and frequencies of MAIT cells in all immune organs and lungs and blocked thymic MAIT cell maturation through downregulating PLZF expression. Strikingly, upregulated miR-155 promoted MAIT1 differentiation and blocked MAIT17 differentiation, and timely inducible expression of miR-155 functionally inhibited peripheral MAIT cells secreting IL-17. miR-155 overexpression also increased CD4–CD8+ subset and decreased CD4–CD8– subset of MAIT cells. We further analyzed MAIT cells in conventional miR-155 knockout mice and found that lack of miR-155 also promoted MAIT1 differentiation and blocked MAIT17 differentiation but without alteration of their overall frequency, maturation and function. Overall, our results indicate that adequate miR-155 expression is required for normal MAIT1 and MAIT17 cell development and function.

CXCL12-CXCR4-Mediated Chemotaxis Supports Accumulation of Mucosal-Associated Invariant T Cells Into the Liver of Patients With PBC.

Objectives: To explore the potential role of CD3+CD8+CD161high TCRVα7.2+ mucosal-associated invariant T (MAIT) cells in the pathogenesis of primary biliary cholangitis (PBC).Methods: We enrolled 55 patients with PBC, 69 healthy controls (HCs), and 8 patients with hepatic hemangioma. Circulating MAIT cells and their chemokine receptor profiles and cytokine production were quantified using flow cytometry. Liver-resident MAIT cells were examined by immunofluorescence staining. CXCL12-mediated chemotaxis of MAIT cells was measured using a transwell migration assay. Plasma interleukin (IL)-18 was measured using ELISA, and cytokine production in IL-18-stimulated MAIT cells was detected using flow cytometry.Result: Peripheral MAIT cells were found to be significantly lower in patients with PBC (3.0 ± 3.2% vs. 9.4 ± 8.0%, p < 0.01) and negatively correlated with alkaline phosphatase (ALP) levels (r = −0.3209, p < 0.05). Liver immunofluorescence staining suggested that MAIT cells might accumulate in PBC liver. MAIT cells from patients with PBC expressed higher levels of CXCR4 (84.8 ± 18.0% vs. 58.7 ± 11.4%, p < 0.01), and the expression of CXCL12 was higher in PBC liver. CXCL12 promoted MAIT cell chemotaxis (70.4 ± 6.8% vs. 52.2 ± 3.5%, p < 0.01), which was attenuated by CXCR4 antagonist. MAIT cells from PBC produced significantly more interferon-γ (IFN-γ) (88.3 ± 4.2% vs. 64.2 ± 10.1%, p < 0.01), tumor necrosis factor-α (TNF-α) (93.0 ± 1.1% vs. 80.1 ± 5.3%, p < 0.01), Granzyme B (89.3 ± 3.3% vs. 72.1 ± 7.0%, p < 0.01), and perforin (46.8 ± 6.6% vs. 34.8 ± 7.7%, p < 0.05). MAIT cells from PBC expressed higher levels of IL18-Rα (83.8 ± 10.2% vs. 58.3 ± 8.7%, p < 0.01). Plasma IL-18 was more abundant in patients with PBC (286.8 ± 75.7 pg/ml vs. 132.9 ± 78.1 pg/ml, p < 0.01). IL-18 promoted IFN-γ production in MAIT cells (74.9 ± 6.6% vs. 54.7 ± 6.7%, p < 0.01), which was partially attenuated by blocking IL-18R (68.6 ± 8.3% vs. 43.5 ± 4.2%, p < 0.01).Conclusion: Mucosal-associated invariant T cells from patients with PBC accumulated in the liver via CXCL12-CXCR4-mediated chemotaxis, produced pro-inflammatory cytokines, and contributed to portal inflammation, which was potentially mediated by elevated IL-18. Targeting MAIT cells might be a therapeutic approach for PBC.

Mucosal-associated invariant T-cells are severely reduced and exhausted in humans with chronic HBV infection.

Chronic hepatitis B virus (CHBV) infection is a major cause of liver diseases. Mucosal-associated invariant T (MAIT) cells are important for antiviral immunity in the liver, but the distinction between intrasinusoidal and peripheral MAIT cells in patients with CHBV infections remains unclear. PBMCs were obtained from patients with CHBV infections (n=29) and age-matched controls (n=46). Liver-associated mononuclear cells (LMCs) were collected from healthy donors (n=29) and explanted livers (n=19) from patients and used for phenotypic, functional and TCR diversity analyses. The percentages of both peripheral and intrasinusoidal MAIT cells were significantly reduced in the CHBV infection group compared to the control group. Peripheral MAIT cells from CHBV-infected patients expressed higher levels of HLA-DR, CD69, CD38 and PD-1 than those of controls. We also confirmed that peripheral MAIT cells in HBV patients had elevated expression T-cell exhaustion genes. Except for a difference in the level of PD-1, no differences were observed between the liver MAIT cells of the two groups. The production of IFN-α in peripheral MAIT cells of CHBV infection patients was lower than in control patients, but no such difference was observed in liver MAIT cells. Additionally, a distinct TCR signature was found in CHBV patients. Hence, we found distinct activities and functions in liver and peripheral MAIT cells of patients with CHBV infections.

Investigation of mucosal-associated invariant T (MAIT) cells expressing immune checkpoint receptors (TIGIT and CD226) in early-onset preeclampsia

ObjectiveDuring our work, we examined the possible contribution of MAIT cells in the pathogenesis of the clinical phase of early-onset preeclampsia and how this could be influenced by TIGIT and CD226 immune checkpoint molecules. Study Design37 pregnant women diagnosed with early-onset preeclampsia and 36 healthy, age-matched control women were involved in this study. Peripheral blood mononuclear cells were isolated by density gradient and frozen. After thawing, cells were stained with monoclonal antibodies to characterize MAIT, MAIT-like, and non-MAIT cells. Flow cytometric analyses were used to measure TIGIT, CD226, intracellular perforin, and granzyme B expression. ResultsMAIT (CD3+ CD8+ Vα7.2+ CD161++), MAIT-like (CD3+ CD8+ Vα7.2+ CD161+) and non-MAIT (CD3+ CD8+ Vα7.2+ CD161-) cell population were identified based on their CD161 receptor positivity. MAIT cells markedly differed in proportion, TIGIT expression, granzyme B, and perforin content compared to MAIT-like and non-MAIT cells. A significant difference was determined in TIGIT expression by non-MAIT cells and in CD8/CD226 positive relationship between the preeclamptic and healthy condition. ConclusionsConsidering that we did not detect a notable difference between early-onset preeclampsia and healthy pregnancy, we suppose that peripheral MAIT cells expressing TIGIT and CD226 immune checkpoint molecules have a marginal role in the pathogenesis of early-onset preeclampsia.

Sustained IFN-I stimulation impairs MAIT cell responses to bacteria by inducing IL-10 during chronic HIV-1 infection.

Mucosal-associated invariant T (MAIT) cells in HIV-1-infected individuals are functionally impaired by poorly understood mechanisms. Single-cell transcriptional and surface protein analyses revealed that peripheral MAIT cells from HIV-1-infected subjects were highly activated with the up-regulation of interferon (IFN)-stimulated genes as compared to healthy individuals. Sustained IFN-α treatment suppressed MAIT cell responses to Escherichia coli by triggering high-level interleukin-10 (IL-10) production by monocytes, which subsequently inhibited the secretion of IL-12, a crucial costimulatory cytokine for MAIT cell activation. Blocking IFN-α or IL-10 receptors prevented MAIT cell dysfunction induced by HIV-1 exposure in vitro. Moreover, blocking the IL-10 receptor significantly improved anti-Mycobacterium tuberculosis responses of MAIT cells from HIV-1-infected patients. Our findings demonstrate the central role of the IFN-I/IL-10 axis in MAIT cell dysfunction during HIV-1 infection, which has implications for the development of anti-IFN-I/IL-10 strategies against bacterial coinfections in HIV-1-infected patients.

Deficiency in Peripheral MAIT Cells But Not in Intrahepatic MAIT Cells in Humans with CHBV Infection

Background: Chronic hepatitis B virus (CHBV) infection is a major cause of liver diseases. Mucosal-associated invariant T (MAIT) cells are important for antiviral immunity in the liver, but the distinction between intrasinusoidal MAIT cells and peripheral MAIT cells in patients with CHBV infection remains unclear. Methods: PBMC were obtained from patients with CHBV infection (n=51) and age-matched controls (n=52). Liver-associated mononuclear cells (LMCs) were collected from donors (n=32) and explanted liver (n=23) of patients to perform phenotypic, functional and TCR diversity analysis. Results: The frequency of intrasinusoidal MAIT cells in the CHBV infection group was not changed compared to that of the MAIT cells in the CHBV-negative group. However, the frequency of peripheral blood MAIT cells was severely reduced in the CHBV infection group compared to the CHBV-negative group. Moreover, IFN-γ production was intact in the intrahepatic MAIT cells of the CHBV infection patients compared to those of the control subjects post IL-12 and IL-18 stimulation, while it was reduced in the peripheral blood MAIT cells of the CHBV infection patients. More importantly, our study showed that the expression level of HLA-DR in peripheral MAIT cells was higher than that in intrasinusoidal MAIT cells in CHBV infection patients. A distinct signature of TCR usage was found in the CHBV patients. Conclusions: By analysing the phenotype, function and TCR usage of MAIT cells in the PBMC and LMC populations of patients with CHBV infection, we found distinct functions and activities in the MAIT cells of the liver compared with those of the peripheral blood. Funding Statement: YG is supported by Natural Science Foundation of Guangdong Province (Grant number: 2018A030313019) and National Natural Science Foundation of China (Grant number:31800758). Declaration of Interests: All authors disclose no conflicts of interest. Ethics Approval Statement: This study was fully approved by the First Affiliated Hospital of Sun Yat-sen University ethical board. All participants provided written informed consent before sample collection.

Alcohol abstinence partially restores peripheral mucosal-associated invariant T cells in patients with alcoholic hepatitis

Abstract Alcoholic hepatitis (AH) develops in a small percentage of heavy drinkers. The adaptive immune system of AH patients is hyper-activated, yet dysregulated and ineffective against infectious diseases. Mucosal-associated invariant T (MAIT) cells are innate-like lymphocytes that are found in liver, intestinal mucosa, and peripheral blood and contribute to protection against infectious diseases. To determine whether MAIT cells were dysregulated in heavy drinkers and the effect of alcohol abstinence on MAIT cell recovery, we compared peripheral MAIT cells between AH patients and heavy drinkers without liver disease (HDC) at baseline and 6- and 12-month followup. At baseline, AH patients had severely reduced frequency of MAIT cells than HDC and healthy donor controls (HC), whereas MAIT cell frequency was not significantly different between HDC and HC. In addition, MAIT cells in AH patients expressed higher levels of the activation markers (CD69, CD38, and HLA-DR) as well as the immune checkpoint inhibitor PD-1. Multiplex immunoassays showed that plasma levels of several cytokines related to MAIT cell activation were elevated in AH patients (IFN-s, IL-7, IL-15, IL-17, IL-18, and IL-23, and TNF-a). In AH patients, the frequency MAIT cells and CD38-expressing MAIT cells correlated with levels of several cytokines and AST. At followup, AH patients had increased MAIT cell frequency and decreased MAIT cell activation with cessation of alcohol. However, abstinent AH patients still had higher levels of CD38-expressing MAIT cells than HDC at 6-month followup. Conclusion Blood MAIT cells were severely reduced and were dysregulated in AH patients and alcohol abstinence partially reversed abnormalities in MAIT cell frequency and phenotype.

Mucosal-Associated Invariant T Cells Are More Activated in Chronic Hepatitis B, but Not Depleted in Blood: Reversal by Antiviral Therapy.

Mucosal-associated invariant T (MAIT) cells might play a role in control of viral replication during chronic hepatitis B (cHBV) infection, but little is known of their number, phenotype, or function in cHBV patients. We performed flow cytometry on CD3+Vɑ7.2+CD161+ MAIT cells in blood of 55 cHBV patients. Nine patients were sampled before and on entecavir treatment. Six patients on therapy underwent a liver biopsy for flow cytometric analysis. Measurements included MAIT cell frequency, phenotype, and cytokine-producing capacity. The MAIT cells were not deleted in blood or liver of cHBV patients compared with healthy controls, but they had higher percentages of CD38+ MAIT cells in blood, which declined on entecavir treatment. Peripheral MAIT cells of patients in the HBeAg-negative phase were least activated. Cytokine-producing MAIT cells were as frequent, but granzyme B-producing MAIT cells were more frequent upon stimulation with Escherichia coli compared with healthy controls. We demonstrate that, in sharp contrast to hepatitis C virus and human immunodeficiency virus patients, MAIT cells isolated from HBV patients are not deleted but are more activated, which can be normalized by nucleoside analog therapy. These observations may aid in deciphering the role of MAIT cells in immune responses to HBV.