Mucosal-Associated Invariant T Cells in Multiple Sclerosis: The Jury is Still Out

Current Perspectives and Challenges of MAIT Cell-Directed Therapy for Tuberculosis Infection

Mucosal-associated invariant T (MAIT) cells are a distinct population of non-conventional T cells that have been preserved through evolution and possess properties of both innate and adaptive immune cells. They are activated through the recognition of antigens presented by non-polymorphic MR1 proteins or, alternately, can be stimulated by specific cytokines. These cells are multifaceted and exert robust antimicrobial activity against bacterial and viral infections, direct the immune response through the modulation of other immune cells, and exhibit a specialized tissue homeostasis and repair function. These distinct characteristics have instigated interest in MAIT cell biology for immunotherapy and vaccine development. This review describes the current understanding of MAIT cell activation, their role in infections and diseases with an emphasis on tuberculosis (TB) infection, and perspectives on the future use of MAIT cells in immune-mediated therapy.

The role of innate lymphocytes in regulating brain and cognitive function

Mounting evidence indicates complex interaction between the immune system and the nervous system, challenging the traditional view about the immune privilege of the brain. Innate lymphoid cells (ILCs) and innate-like T cells are unique families of immune cells that functionally mirror traditional T cells but may function via antigen- and T cell antigen receptor (TCR)-independent mechanisms. Recent work indicates that various ILCs and innate-like T cell subsets are present in the brain barrier tissue, where they play important roles in regulating brain barrier integrity, brain homeostasis and cognitive function. In this review, we discuss recent advances in understanding the intricate roles for innate and innate-like lymphocytes in regulating brain and cognitive function.

MAIT Cell Development and Functions: the Microbial Connection

Mucosal-associated invariant T (MAIT) cells are an evolutionarily conserved T cell subset, which reacts to most bacteria through T cell receptor (TCR)-mediated recognition of metabolites derived from the vitamin B2 biosynthetic pathway. Microbiota-derived signals affect all stages of MAIT cell biology including intra-thymic development, peripheral expansion, and functions in specific organs. In tissues, MAIT cells can integrate multiple signals and display effector functions involved in the defense against infectious pathogens. In addition to anti-bacterial activity, MAIT cells improve wound healing in the skin, suggesting a role in epithelium homeostasis through bi-directional interactions with the local microbiota. In humans, blood MAIT cell frequency is modified during several auto-immune diseases, which are often associated with microbiota dysbiosis, further emphasizing the potential interplay of MAIT cells with the microbiota. Here, we will review how microbes interact with MAIT cells, from initial intra-thymic development to tissue colonization and functions.

Role of Peripheral Immune Cells in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the myelination of the neurons present in the central nervous system (CNS). The exact etiology of MS development is unclear, but various environmental and genetic factors might play a role in initiating the disease. Experimental autoimmune encephalomyelitis (EAE) is a mouse model that is used to study the pathophysiology of MS disease as well as the effects of possible therapeutic agents. In addition, autoreactive immune cells trigger an inflammatory process upon the recognition of CNS antigens, which leads to destruction of the neurons. These include innate immune cells such as macrophages, dendritic cells, and natural killer cells. Additionally, the activation and extravasation of adaptive immune cells such as CD4+ T cells into the CNS may lead to further exacerbation of the disease. However, many studies revealed that immune cells could have either a protective or pathological role in MS. In this review, we highlight the roles of innate and adaptive immune cellular and soluble players that contribute to the pathogenesis of MS and EAE, which may be used as potential targets for therapy.

Saliva immunoglobulin free light chain analysis for monitoring disease activity and response to treatment in multiple sclerosis

BACKGROUND

Immunoglobulin free light chains (FLC) have recently gained considerable interest as new promising intrathecal biomarkers of multiple sclerosis (MS). However, lumbar puncture is invasive and not practical for monitoring disease course. This study aimed to assess the utility of saliva FLC as a biomarker of disease activity and response to treatment in MS METHODS: Western blotting was used to study saliva FLC monomers and dimers. The intensity of immunoreactive FLC bands was quantified by electrophoresis analysis, and the obtained values were used as FLC indices to account for kappa and lambda FLC monomer and dimer levels. Firth's logistic regression analysis suitable to study small cohorts was applied to compare FLC levels between M.S. patients in relapse, MS patients in remission, and healthy controls. Association between FLC levels and clinical and radiological parameters was analyzed.

RESULTS

55 MS patients and 40 healthy controls were evaluated. Saliva FLC levels were significantly higher in relapse compared to remission. Logistic regression analysis employing a combination of FLC indices confirmed the significant difference between these two groups. The FLC levels were significantly reduced by treatment with corticosteroids. During remission, patients treated with disease-modifying therapies had lower levels of FLC compared to untreated patients. The increased FLC levels were associated with the presence of gadolinium-enhancing lesions, but not with MRI T2 lesion load and EDSS scores. During individual patient follow-up, the changes of the saliva FLC levels were in concordance with the disease activity status.

CONCLUSIONS

Saliva FLC levels may be a useful biomarker for discriminating between stable remission and active disease. The developed test may serve as a new, non-invasive, and inexpensive tool for monitoring disease activity and response to treatment in MS.

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

OBJECTIVE

During 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 DESIGN

37 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.

RESULTS

MAIT (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.

CONCLUSIONS

Considering 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.

Mucosal-Associated Invariant T Cell Features and TCR Repertoire Characteristics During the Course of Multiple Sclerosis

Objective: To investigate the frequency, phenotype, function, and longitudinal repertoire of mucosal-associated invariant T (MAIT) cells in relapsing remitting multiple sclerosis (RRMS) and primary progressive multiple sclerosis (PPMS) patients.

Methods: Forty-five RRMS patients in remission, 20 RRMS patients experiencing exacerbations, 15 PPMS patients, and 30 healthy controls (HCs) were included in the study. MAIT cells were identified phenotypically as CD3⁺ TCRγδ⁻ Vα7.2 + CD161^high. In 15 patients, MAIT cell number and MRI lesions were evaluated every 6 months, for 36 months. MAIT cell TCRVβ repertoire was defined using single-cell cloning and mRNA sequencing.

Results: Circulating MAIT cells were significantly reduced in both RRMS and PPMS patients, particularly during exacerbations, compared to healthy subjects. This decrease was accompanied by pro-inflammatory cytokine production (TNF-α, IFN-γ, IL-17, and GM-CSF). Three months post-exacerbation, peripheral blood MAIT cell percentages increased significantly along with clinical recovery. Likewise, we observed inverse correlation between MRI lesions and peripheral blood MAIT cell numbers. In paired samples, MAIT cell percentage was significantly higher in CSF than in peripheral blood, suggesting MAIT cell migration through the blood–brain barrier. Finally, MAIT cells showed limited TCRVβ repertoires, in both CSF and peripheral blood, which remained stable over time.

Conclusions: MAIT cell levels correlated with MS course both clinically and radiologically, showing marked and sustained oligoclonality. These findings may contribute to a better understanding of pathophysiological phenomena underlying the course of MS, and discovery of MAIT cell inhibitors could pave the way for the development of new therapeutic strategies.

MAIT cell subtypes in multiple sclerosis

In patients with multiple sclerosis (MS) and healthy controls (HC) we studied circulating MAIT cells and MAIT cell subtypes expressing CXCR3 and CCR6 by flow cytometry. Absolute numbers of MAIT cells and specifically Tc17-like MAIT cells were lower in patients with primary progressive MS (PPMS) than in controls. Low numbers of Tc17-like MAIT cells were associated with smoking and high concentrations of myelin basic protein in the cerebrospinal fluid. Treatment with alemtuzumab and dimethyl fumarate decreased MAIT cell frequencies. Altogether, we have identified specific MAIT cell subtypes related to PPMS, smoking and demyelination, and MAIT cell effects of MS therapies.

Mucosal-Associated Invariant T Cells Display Diminished Effector Capacity in Oesophageal Adenocarcinoma

Oesophageal adenocarcinoma (OAC) is an aggressive malignancy with poor prognosis, and incidence is increasing rapidly in the Western world. Mucosal-associated invariant T (MAIT) cells recognize bacterial metabolites and kill infected cells, yet their role in OAC is unknown. We aimed to elucidate the role of MAIT cells during cancer development by characterizing the frequency, phenotype, and function of MAIT cells in human blood and tissues, from OAC and its pre-malignant inflammatory condition Barrett's oesophagus (BO). Blood and tissues were phenotyped by flow cytometry and conditioned media from explanted tissue was used to model the effects of the tumor microenvironment on MAIT cell function. Associations were assessed between MAIT cell frequency, circulating inflammatory markers, and clinical parameters to elucidate the role of MAIT cells in inflammation driven cancer. MAIT cells were decreased in BO and OAC blood compared to healthy controls, but were increased in oesophageal tissues, compared to BO-adjacent tissue, and remained detectable after neo-adjuvant treatment. MAIT cells in tumors expressed CD8, PD-1, and NKG2A but lower NKG2D than BO cohorts. MAIT cells produced less IFN-γ and TNF-α in the presence of tumor-conditioned media. OAC cell line viability was reduced upon exposure to expanded MAIT cells. Serum levels of chemokine IP-10 were inversely correlated with MAIT cell frequency in both tumors and blood. MAIT cells were higher in the tumors of node-negative patients, but were not significantly associated with other clinical parameters. This study demonstrates that OAC tumors are infiltrated by MAIT cells, a type of CD8 T cell featuring immune checkpoint expression and cytotoxic potential. These findings may have implications for immunotherapy and immune scoring approaches.

Perfluorinated substances, risk factors for multiple sclerosis and cellular immune activation

Perfluorinated alkylated substances (PFASs) have immunomodulatory effects but the impact on multiple sclerosis (MS) and cellular immune functions is only sparsely described. In the present study, we found lower concentrations of the long chain PFAS perfluorooctane sulfonic acid (PFOS) in MS than in healthy controls (HC). In HC, we did not detect associations between PFOS concentrations and immune phenotypes. Analyzing the impact of known MS risk factors on cellular immune functions, we found that smoking and Epstein-Barr nuclear antigen 1 antibodies were associated with distinct circulating immune cell changes. In summary, current background PFAS exposure is not an important risk factor for MS.

Tumor-infiltrating mucosal-associated invariant T (MAIT) cells retain expression of cytotoxic effector molecules

Mucosal-associated invariant T (MAIT) cells all express a semi-invariable T cell receptor recognizing microbial metabolites presented on the MHC class I-like molecule MR1. Upon activation, they rapidly secrete cytokines and increase their cytotoxic potential. We showed recently that MAIT cells with Th1 phenotype accumulate in human colon adenocarcinomas. Here, we investigated the cytotoxic potential of tumor-infiltrating MAIT cells in colon adenocarcinomas, and to what extent it may be affected by the tumor microenvironment. Activation of MAIT cells from tumors induced increased Granzyme B, and to a lesser extent, perforin expression. Degranulation was assessed by surface expression of CD107a, and was also seen in response to cognate antigen recognition. The cytotoxic potential of tumor-associated MAIT cells was very similar to that of MAIT cells from unaffected colon. MAIT cells were also identified by immunofluorescence in direct contact with tumor cells in sections from colon cancer specimens. To summarize, tumor-associated MAIT cells from colon tumors have strong cytotoxic potential and are not compromised in this regard compared to MAIT cells from the unaffected colon. We conclude that MAIT cells may contribute significantly to the protective immune response to tumors, both by secretion of Th1-associated cytokines and by direct killing of tumor cells.

Innate, innate-like and adaptive lymphocytes in the pathogenesis of MS and EAE

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) in which the immune system damages the protective insulation surrounding the nerve fibers that project from neurons. A hallmark of MS and its animal model, experimental autoimmune encephalomyelitis (EAE), is autoimmunity against proteins of the myelin sheath. Most studies in this field have focused on the roles of CD4⁺ T lymphocytes, which form part of the adaptive immune system as both mediators and regulators in disease pathogenesis. Consequently, the treatments for MS often target the inflammatory CD4⁺ T-cell responses. However, many other lymphocyte subsets contribute to the pathophysiology of MS and EAE, and these subsets include CD8⁺ T cells and B cells of the adaptive immune system, lymphocytes of the innate immune system such as natural killer cells, and subsets of innate-like T and B lymphocytes such as γδ T cells, natural killer T cells, and mucosal-associated invariant T cells. Several of these lymphocyte subsets can act as mediators of CNS inflammation, whereas others exhibit immunoregulatory functions in disease. Importantly, the efficacy of some MS treatments might be mediated in part by effects on lymphocytes other than CD4⁺ T cells. Here we review the contributions of distinct subsets of lymphocytes on the pathogenesis of MS and EAE, with an emphasis on lymphocytes other than CD4⁺ T cells. A better understanding of the distinct lymphocyte subsets that contribute to the pathophysiology of MS and its experimental models will inform the development of novel therapeutic approaches.

Production of IL-17 by MAIT Cells Is Increased in Multiple Sclerosis and Is Associated with IL-7 Receptor Expression

Multiple sclerosis (MS) is a T cell-driven inflammatory disease of the CNS. Research on T cell subsets involved in MS pathogenesis has mainly focused on classical CD4⁺ T cells, especially Th17 cells, as they produce the proinflammatory, MS-associated cytokine IL-17. However, the abundant unconventional mucosal-associated invariant T (MAIT) cells are also able to produce IL-17. MAIT cells are characterized by high CD161 expression and a semi-invariant Vα7.2 TCR, with which they recognize bacterial and yeast Ags derived from the riboflavin (vitamin B2) metabolism. In this study, we characterized MAIT cells from the peripheral blood of MS patients in comparison with healthy individuals with respect to their type-17 differentiation. We found a specific increase of IL-17⁺ MAIT cells as well as an increased expression of retinoic acid-related orphan receptor (ROR)γt and CCR6 in MAIT cells from MS patients, whereas the expression of T cell activation markers HLA-DR and CD38 was not different. IL-17 production by MAIT cells furthermore correlated with the surface expression level of the IL-7 receptor α-chain (CD127), which was significantly increased on MAIT cells from MS patients in comparison with healthy individuals. In summary, our findings indicate an augmented type-17 differentiation of MAIT cells in MS patients associated with their IL-7 receptor surface expression, implicating a proinflammatory role of these unconventional T cells in MS immunopathology.

MHC class I-related molecule, MR1, and mucosal-associated invariant T cells

The MHC-related 1, MR1, molecule presents a new class of microbial antigens (derivatives of the riboflavin [Vitamin B2] biosynthesis pathway) to mucosal-associated invariant T (MAIT) cells. This raises many questions regarding antigens loading and intracellular trafficking of the MR1/ligand complexes. The MR1/MAIT field is also important because MAIT cells are very abundant in humans and their frequency is modified in many infectious and non-infectious diseases. Both MR1 and the invariant TCRα chain expressed by MAIT cells are strikingly conserved among species, indicating important functions. Riboflavin is synthesized by plants and most bacteria and yeasts but not animals, and its precursor derivatives activating MAIT cells are short-lived unless bound to MR1. The recognition of MR1 loaded with these compounds is therefore an exquisite manner to detect invasive bacteria. Herein, we provide an historical perspective of the field before describing the main characteristics of MR1, its ligands, and the few available data regarding its cellular biology. We then summarize the current knowledge of MAIT cell differentiation and discuss the definition of MAIT cells in comparison to related subsets. Finally, we describe the phenotype and effector activities of MAIT cells.

Gut-CNS-Axis as Possibility to Modulate Inflammatory Disease Activity-Implications for Multiple Sclerosis

In the last decade the role of environmental factors as modulators of disease activity and progression has received increasing attention. In contrast to classical environmental modulators such as exposure to sun-light or fine dust pollution, nutrition is an ideal tool for a personalized human intervention. Various studies demonstrate a key role of dietary factors in autoimmune diseases including Inflammatory Bowel Disease (IBD), rheumatoid arthritis or inflammatory central nervous system (CNS) diseases such as Multiple Sclerosis (MS). In this review we discuss the connection between diet and inflammatory processes via the gut-CNS-axis. This axis describes a bi-directional communication system and comprises neuronal signaling, neuroendocrine pathways and modulation of immune responses. Therefore, the gut-CNS-axis represents an emerging target to modify CNS inflammatory activity ultimately opening new avenues for complementary and adjunctive treatment of autoimmune diseases such as MS.

The contrasting roles of Th17 immunity in human health and disease

The human immune system is a tightly regulated network that protects the host from disease. An important aspect of this is the balance between pro-inflammatory Th17 cells and anti-inflammatory T regulatory (Treg) cells in maintaining immune homeostasis. Foxp3+ Treg are critical for sustaining immune tolerance through IL-10 and transforming growth factor-β while related orphan receptor-γt+ Th17 cells promote immunopathology and auto-inflammatory diseases through the actions of IL-17A, IL-21 and IL-22. Therefore, imbalance between Treg and Th17 cells can result in serious pathology in many organs and tissues. Recently, certain IL-17-producing cells have been found to be protective against infectious disease, particularly in relation to extracellular bacteria such Streptococcus pneumoniae; a number of other novel IL-17-secreting cell populations have also been reported to protect against a variety of other pathogens. In this mini-review, the dual roles of Treg and Th17 cells are discussed in the context of autoimmunity and infections, highlighting recent advances in the field. Development of novel strategies specifically designed to target these critical immune response pathways will become increasingly important in maintenance of human health.

MAIT cells are reduced in frequency and functionally impaired in human T lymphotropic virus type 1 infection: Potential clinical implications

HTLV-1 infection is associated with several inflammatory disorders, including the neurodegenerative condition HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is unclear why a minority of infected subjects develop HAM/TSP. The cellular immune response has been implicated in the development of inflammatory alterations in these patients; however the pathogenic mechanisms for disease progression remain unclear. Furthermore, HTLV-1-infected individuals have an increase incidence of Mycobacterium tuberculosis (Mtb) infection, suggesting that immunological defect are associated with HTLV-1 infection. Evidence suggests an important role for Mucosal-associated invariant T (MAIT) cells in the early control of Mtb infection. Chronic viral infections like HIV and HCV have been associated with decreased frequency and functionality of MAIT cells. We hypothesized that HTLV-1 infection is associated with similar perturbations in MAIT cells. We investigated MAIT cell frequency, phenotype, and function by flow cytometry in a cohort of 10 asymptomatic and 10 HAM/TSP HTLV-1 infected patients. We found that MAIT cells from HTLV-1-infected subjects were reduced and showed high co-expression of the activation markers CD38 and HLA-DR but normal levels of CCR6 and CD127. MAIT cells had a lower expression of the transcription factor PLZF in HAM/TSP patients. Unlike Tax-specific CD8+T cells, which are hyperfunctional, MAIT cells from HTLV-1-infected subjects had a poor IFNγ response following antigen stimulation. MAIT cell perturbations in HTLV-1 infection were not associated with HTLV-1 proviral load and MAIT cells were not infected by HTLV-1 in vivo. Rather, MAIT cells loss was associated with immune activation. Overall, our results do not support a role for MAIT cells in HAM/TSP pathogenesis but reduced numbers of MAIT cells, together with their poor functionality, could contribute to the increased susceptibility of HTLV-1-infected individuals to other infectious agents.

High Interferon-γ Uniquely in Vδ1 T Cells Correlates with Markers of Inflammation and Axonal Damage in Early Multiple Sclerosis

We have identified a population of T lymphocytes in peripheral blood, Vδ1 TCRγδ T lymphocytes, which unexpectedly was uniquely expressing high production of interferon-γ in newly diagnosed, untreated multiple sclerosis (MS) patients. IFN-γ production in this population distinctly correlated to parameters of clinical disease activity, inflammation, and neuronal damage. These Vδ1 T lymphocytes belong to a population of innate T lymphocytes that recognize antigen in the context of CD1d/CD1c and which include reactivity to the myelin glycosphingolipid sulfatide. Importantly, patients treated with natalizumab, blocking leukocyte transmigration to central nervous system, had completely normalized levels of interferon-γ-producing Vδ1 T lymphocytes. A biomarker and early sign of demyelinating disease in MS is much warranted and would help identify immunopathogenesis and prognosis of disease as well as monitor success with adequate treatment. The present study identifies the Vδ1 T lymphocytes as an early marker of MS and a possible link to understanding the disease etiology.

T cell responses in the central nervous system

T cells are required for immune surveillance of the central nervous system (CNS); however, they can also induce severe immunopathology in the context of both viral infections and autoimmunity. The mechanisms that are involved in the priming and recruitment of T cells to the CNS are only partially understood, but there has been renewed interest in this topic since the 'rediscovery' of lymphatic drainage from the CNS. Moreover, tissue-resident memory T cells have been detected in the CNS and are increasingly recognized as an autonomous line of host defence. In this Review, we highlight the main mechanisms that are involved in the priming and CNS recruitment of CD4⁺ T cells, CD8⁺ T cells and regulatory T cells. We also consider the plasticity of T cell responses in the CNS, with a focus on viral infection and autoimmunity.

Invariant natural killer T cells and mucosal-associated invariant T cells in multiple sclerosis

Multiple sclerosis (MS) is a chronic progressive inflammatory demyelinating disorder of the central nervous system, and in several countries is a leading cause of permanent neurological disability in young adults, particularly women. MS is considered an autoimmune disease, caused by an aberrant immune response to environmental triggers in genetically susceptible subjects. However, the contribution of the innate or of the adaptive immune system to the development and progression of the disease has not yet been fully elucidated. Innate-like T lymphocytes are unconventional T cells that bridge the innate and adaptive arms of the immune system, because they use a T cell receptor to sense external ligands, but behave like innate cells when they rapidly respond to stimuli. These cells could play an important role in the pathogenesis of MS. Here, we focus on invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells, and we review the current knowledge on their biology and possible involvement in MS. Although several studies have evaluated the frequency and functions of iNKT and MAIT cells both in MS patients and in experimental mouse models, contradictory observations have been reported, and it is not clear whether they exert a protective or a pro-inflammatory and harmful role. A better understanding of how immune cells are involved in MS, and of their interactions could be of great interest for the development of new therapeutic strategies.

What rheumatologists need to know about innate lymphocytes

Many rheumatic diseases are characterized by having an autoimmune background. Determining the mechanisms underlying autoimmunity is, therefore, important to further understand these diseases and to inform future lines of research aimed at developing new treatments and cures. As fast responders, innate lymphocytes have protective or pathogenic roles in the initiation as well as the maintenance of immune responses in general, and they contribute to tissue homeostasis, among other functions. Innate lymphocytes also seem to be involved in autoimmunity in particular. Since 2010, accumulating evidence clearly shows that different populations of innate lymphocytes have roles in responding to antigen-specific autoantibody and autoreactive T cells, thereby amplifying or attenuating disease processes. Cytotoxicity is a cardinal feature of many innate lymphocytes and can contribute to inflammatory tissue damage. Finally, innate lymphocytes can respond to biologic therapies for autoimmune diseases. Consequently, like TNF and other effector molecules, certain innate lymphocyte subsets might be appropriate therapeutic targets to ameliorate various autoimmune diseases. In this Review, we summarize the main characteristics and functions of innate lymphocyte subsets, and describe their roles in autoimmune disease. We also discuss how biologic therapies influence innate lymphocyte function and consider the potential for these cell subsets to act as future therapeutic targets.

The dynamics of mucosal-associated invariant T cells in multiple sclerosis

Background

Multiple sclerosis (MS) is an autoimmune disease characterized by inflammatory demyelination, gliosis and axonal loss in the Central Nervous System. Although the etiology of the disease has remained enigmatic, recent studies have suggested a role of the innate-like T cells, called Mucosal Associated Invariant T cells (MAITs) in the pathophysiology. In the present study, we have analyzed the relative frequency of MAITs and the expression of the cell surface antigens in MAITs to seek a possible link to the disease.

Results

There was little difference in the frequency of total MAITs between healthy donors (HDs) and untreated MS patients, whereas the latter harbored more CD8^lo/neg (DN) MAITs concomitant with a decrease in CD8^high MAITs and in CD4 MAITs compared with those in HDs. While the expression of CCR5, CCR6, CD95, CD127, and CD150 has increased in untreated subjects compared with that in HDs, CD45RO has declined in untreated subjects in both DN MAITs and CD8^hi MAITs. FTY720 therapy has increased the relative frequency of total MAITs in a time-dependent fashion up to 2 years. Intriguingly, FTY720 therapy for 3 years reversed the above phenotype, engendering more CD8^high MAITs accompanied with decreased DN MAITs. FTY720 therapy affected the cytokine production from CD4 T cells and also enhanced the relative frequency of cells producing both TNF-α and IFN-γ from MAITs, CD8 T cells, and CD4 T cells compared with that in untreated subjects.

Conclusions

FTY 720 therapy enhanced the relative frequency of MAITs in MS patients in a time-dependent manner. Although the expression of CD8 in MAITs has been affected early by FTY720, longer treatment has reversed the phenotypic change. These data demonstrated that FTY720 induced dynamic change in the relative frequency and in the phenotype of MAITs in MS.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2923-9) contains supplementary material, which is available to authorized users.

The role of MHC class Ib-restricted T cells during infection

Even though major histocompatibility complex (MHC) class Ia and many Ib molecules have similarities in structure, MHC class Ib molecules tend to have more specialized functions, which include the presentation of non-peptidic antigens to non-classical T cells. Likewise, non-classical T cells also have unique characteristics, including an innate-like phenotype in naïve animals and rapid effector functions. In this review, we discuss the role of MAIT and NKT cells during infection but also the contribution of less studied MHC class Ib-restricted T cells such as Qa-1-, Qa-2-, and M3-restricted T cells. We focus on describing the types of antigens presented to non-classical T cells, their response and cytokine profile following infection, as well as the overall impact of these T cells to the immune system.