Deficiencies of Circulating Mucosal-associated Invariant T Cells and Natural Killer T Cells in Patients with Acute Cholecystitis

Impacts of ageing on the efficacy of CAR-T cell therapy

Chimeric antigen receptor T cells recognizing CD19 (19CAR-T) cell therapy has achieved robust clinical efficacy when treating some hematological malignancies, but which patient subgroups benefit mostly remains elusive. Here we summarized the data of 541 patients from 30 clinical trials who underwent 19 CAR-T therapy and analyzed the different clinical responses between young (<44 years), middle-aged (45-59 years) and elderly (>60 years) patients and found that the young patients showed a higher level of complete response (CR) rate. Therefore, we then summarize the advances of studies focusing on the effects of age on anti-tumor efficacy of CAR-T therapy and analyze the reasons for the low CR rate after CAR-T cell therapy in elderly patients with tumors, aiming to provide hints for oncologists to select the most suitable candidate for this cancer immunotherapy.

The paradox of aging: Aging-related shifts in T cell function and metabolism

T cell survival, differentiation after stimulation, and function are intrinsically linked to distinct cellular metabolic states. The ability of T cells to readily transition between metabolic states enables flexibility to meet the changing energy demands defined by distinct effector states or T cell lineages. Immune aging is characterized, in part, by the loss of naïve T cells, accumulation of senescent T cells, severe dysfunction in memory phenotype T cells in particular, and elevated levels of inflammatory cytokines, or 'inflammaging'. Here, we review our current understanding of the phenotypic and functional changes that occur with aging in T cells, and how they relate to metabolic changes in the steady state and after T cell activation. We discuss the apparent contradictions in the aging T cell phenotype - where enhanced differentiation states and metabolic profiles in the steady state can correspond to a diminished capacity to adapt metabolically and functionally after T cell activation. Finally, we discuss key recent studies that indicate the enormous potential for aged T cell metabolism to induce systemic inflammaging and organism-wide multimorbidity, resulting in premature death.

Activation, Deficiency, and Reduced IFN-γ Production of Mucosal-Associated Invariant T Cells in Patients with Inflammatory Bowel Disease

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can activate either in response to T-cell receptor (TCR) engagement or through activating cytokines and play an important role in autoimmune disorders. The study examined the level and function of MAIT cells in patients with inflammatory bowel disease (IBD). Circulating MAIT cell levels were significantly reduced in IBD patients. This MAIT cell deficiency was correlated with IBD disease activity grades, hemoglobin, and CRP. IFN-γ production of circulating MAIT cells in response to both MHC class 1b-like related protein (MR1)-dependent and -independent stimulations was decreased in IBD patients, which was partially associated with reduced activation of nuclear factor of activated T cells 1 (NFAT1) transcription factor, a main regulator of IFN-γ production. Expression levels of CD69, programmed death-1 (PD-1), and annexin V in MAIT cells were elevated in IBD patients. CCL20, CXCL10, CXCL16, and CCL25 were expressed higher in inflamed intestinal tissues than in noninflamed tissues. This study demonstrates that circulating MAIT cells are activated and numerically and functionally deficient in IBD patients. Furthermore, activated MAIT cells have the potential to migrate to inflamed tissues. These findings suggest an important role of MAIT cells in mucosal immunity in IBD.

Innate T cells in the intensive care unit

Rapid onset of acute inflammation is a hallmark of critical illnesses that bring patients to the intensive care unit (ICU). In critical illness, innate T cells rapidly reach full activation and drive a robust acute inflammatory response. As "cellular adjuvants," innate T cells worsen inflammation and mortality in several common critical illnesses including sepsis, ischemia-reperfusion injury, stroke, and exacerbations of respiratory disease. Interestingly, innate T cell subsets can also promote a protective and anti-inflammatory response in sepsis, ischemia-reperfusion injury, and asthma. Therapies that target innate T cells have been validated in several models of critical illness. Here, we review the role of natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells and γδ T cells in clinical and experimental critical illness.

Clinical relevance of circulating mucosal-associated invariant T cell levels and their anti-cancer activity in patients with mucosal-associated cancer

Mucosal-associated invariant T (MAIT) cells are an antimicrobial MR1-restricted T cell subset and play an important role in immune defense response to bacteria. However, little is known about the role of MAIT cells in cancer. The aims of this study were to examine the level and function of MAIT cells in cancer patients and to evaluate the clinical relevance of MAIT cell levels. Ninety-nine patients with cancer and 20 healthy controls were included in this study. Circulating MAIT cell levels were significantly reduced in patients with mucosal-associated cancers (MACs), such as gastric, colon and lung cancers, but their capacities for IFN-γ, IL-17, or TNF-α production were preserved. This MAIT cell deficiency was significantly correlated with N staging and carcinoembryonic antigen level. Percentages of MAIT cells were significantly higher in cancer tissue than in peripheral blood and immunofluorescent labeling showed MAIT cell infiltration into colon cancer tissues. Circulating MAIT cells exhibited high levels of CCR6 and CXCR6, and their corresponding chemokines, such as CCL20 and CXCL16, were strongly expressed in colon cancer tissues. Activated MAIT cells not only had lymphokine-activated killer activity, but they also had direct cytotoxicity on K562 cells via degranulation of granzyme B and perforin. This study primarily demonstrates that circulating MAIT cells are reduced in MAC patients due to migration to mucosal cancer tissues and they have the potential to kill cancer cells. In addition, this circulating MAIT cell deficiency is related to the degree of cancer progression in mucosal tissues.

Role of MAIT cells in the immunopathogenesis of inflammatory diseases: New players in old game

Current advances in immunology have led to the identification of a population of novel innate immune T cells, called mucosa-associated invariant T (MAIT) cells. The cells in humans express an invariant TCRα chain (Vα7.2-Jα33) paired with a limited subset of TCRβ chains (Vβ2, 13 and 22), are restricted by the MHC class I (MH1)-related (MR)-1, and recognize molecules that are produced in the bacterial riboflavin (vitamin B2) biosynthetic pathway. They are present in the circulation, liver and at various mucosal sites (i.e. intestine, lungs and female reproductive tract, etc.). They kill host cells infected with bacteria and yeast, and secrete soluble mediators such as TNF-α, IFN-γ, IL-17, etc. The cells regulate immune responses and inflammation associated with a wide spectrum of acute and chronic diseases in humans. Since their discovery in 1993, significant advances have been made in understanding biology of MAIT cells and the potential role of these cells in the pathogenesis of autoimmune, inflammatory and infectious diseases as well as cancer in humans. The purpose of this review is to provide a current state of our knowledge about MAIT cell biology and delineate their role in autoimmune and inflammatory diseases (sterile or caused by infectious agents) and cancer in humans. A better understanding of the role of MAIT cells in human diseases may lead to novel ways of immunotherapies.

Deficiencies of Circulating Mucosal-associated Invariant T Cells and Natural Killer T Cells in Patients with Multiple Trauma

Mucosal-associated invariant T (MAIT) cells and natural killer T (NKT) cells are known to play important roles in autoimmunity, infectious diseases and cancers. However, little is known about the roles of these invariant T cells in multiple trauma. The purposes of this study were to examine MAIT and NKT cell levels in patients with multiple trauma and to investigate potential relationships between these cell levels and clinical parameters. The study cohort was composed of 14 patients with multiple trauma and 22 non-injured healthy controls (HCs). Circulating MAIT and NKT cell levels in the peripheral blood were measured by flow cytometry. The severity of injury was categorised according to the scoring systems, such as Acute Physiology and Chronic Health Evaluation (APACHE) II score, Simplified Acute Physiology Score (SAPS) II, and Injury Severity Score (ISS). Circulating MAIT and NKT cell numbers were significantly lower in multiple trauma patients than in HCs. Linear regression analysis showed that circulating MAIT cell numbers were significantly correlated with age, APACHE II, SAPS II, ISS category, hemoglobin, and platelet count. NKT cell numbers in the peripheral blood were found to be significantly correlated with APACHE II, SAPS II, and ISS category. This study shows numerical deficiencies of circulating MAIT cells and NKT cells in multiple trauma. In addition, these invariant T cell deficiencies were found to be associated with disease severity. These findings provide important information for predicting the prognosis of multiple trauma.

MAIT cells: new guardians of the liver

The liver is an important immunological organ that remains sterile and tolerogenic in homeostasis, despite continual exposure to non-self food and microbial-derived products from the gut. However, where intestinal mucosal defenses are breached or in the presence of a systemic infection, the liver acts as a second 'firewall', because of its enrichment with innate effector cells able to rapidly respond to infections or tissue dysregulation. One of the largest populations of T cells within the human liver are mucosal-associated invariant T (MAIT) cells, a novel innate-like T-cell population that can recognize a highly conserved antigen derived from the microbial riboflavin synthesis pathway. MAIT cells are emerging as significant players in the human immune system, associated with an increasing number of clinical diseases of bacterial, viral, autoimmune and cancerous origin. As reviewed here, we are only beginning to investigate the potential role of this dominant T-cell subset in the liver, but the reactivity of MAIT cells to both inflammatory cytokines and riboflavin derivatives suggests that MAIT cells may have an important role in first line of defense as part of the liver firewall. As such, MAIT cells are promising targets for modulating the host defense and inflammation in both acute and chronic liver diseases.

Activation, Impaired Tumor Necrosis Factor-α Production, and Deficiency of Circulating Mucosal-Associated Invariant T Cells in Patients with Scrub Typhus

BACKGROUND

Mucosal-associated invariant T (MAIT) cells contribute to protection against certain microorganism infections. However, little is known about the role of MAIT cells in Orientia tsutsugamushi infection. Hence, the aims of this study were to examine the level and function of MAIT cells in patients with scrub typhus and to evaluate the clinical relevance of MAIT cell levels.

METHODOLOGY/PRINCIPAL FINDINGS

Thirty-eight patients with scrub typhus and 53 health control subjects were enrolled in the study. The patients were further divided into subgroups according to disease severity. MAIT cell level and function in the peripheral blood were measured by flow cytometry. Circulating MAIT cell levels were found to be significantly reduced in scrub typhus patients. MAIT cell deficiency reflects a variety of clinical conditions. In particular, MAT cell levels reflect disease severity. MAIT cells in scrub typhus patients displayed impaired tumor necrosis factor (TNF)-α production, which was restored during the remission phase. In addition, the impaired production of TNF-α by MAIT cells was associated with elevated CD69 expression.

CONCLUSIONS

This study shows that circulating MAIT cells are activated, numerically deficient, and functionally impaired in TNF-α production in patients with scrub typhus. These abnormalities possibly contribute to immune system dysregulation in scrub typhus infection.

Mucosal-associated invariant T cells from induced pluripotent stem cells: A novel approach for modeling human diseases

Mice have frequently been used to model human diseases involving immune dysregulation such as autoimmune and inflammatory diseases. These models help elucidate the mechanisms underlying the disease and in the development of novel therapies. However, if mice are deficient in certain cells and/or effectors associated with human diseases, how can their functions be investigated in this species? Mucosal-associated invariant T (MAIT) cells, a novel innate-like T cell family member, are a good example. MAIT cells are abundant in humans but scarce in laboratory mice. MAIT cells harbor an invariant T cell receptor and recognize nonpeptidic antigens vitamin B2 metabolites from bacteria and yeasts. Recent studies have shown that MAIT cells play a pivotal role in human diseases such as bacterial infections and autoimmune and inflammatory diseases. MAIT cells possess granulysin, a human-specific effector molecule, but granulysin and its homologue are absent in mice. Furthermore, MAIT cells show poor proliferation in vitro. To overcome these problems and further our knowledge of MAIT cells, we have established a method to expand MAIT cells via induced pluripotent stem cells (iPSCs). In this review, we describe recent advances in the field of MAIT cell research and our approach for human disease modeling with iPSC-derived MAIT cells.

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

The immune system is strongly implicated in the pathophysiology of multiple sclerosis (MS), as demonstrated by the efficacy of therapies targeting various components of adaptive immunity. However, the disease still progresses despite these treatments in many patients, while others experience life-threatening adverse effects, urging for the discovery of new immune-targeting medications. Among the immune cell types participating to MS pathogenesis, decades of work have highlighted the prominent role of CD4 T cells. More recent data demonstrate the involvement of CD8 T cells as well. The existence of both pathogenic and protective CD8 T cells subsets has been suggested, adding an additional layer of complexity to the picture. Mucosal-associated invariant T (MAIT) cells are innate-like lymphocytes that make up to 25% of CD8 T cells in healthy subjects. They are specific for conserved microbial ligands and may constitute an important barrier against invasive bacterial and fungal infection. An increasing number of reports also suggest their possible involvement in chronic inflammatory diseases, including MS. MAIT cells could participate through their ability to produce IFNγ and/or IL-17, two major cytokines in the pathogenesis of several chronic inflammatory/autoimmune diseases. However, the mechanisms by which MAIT cells could be activated in these sterile conditions are not known. Furthermore, contradictory observations have been made, reporting either a protective or a pro-inflammatory behavior of MAIT cells in MS or its murine model, experimental autoimmune encephalomyelitis. In this review article, we will describe the current knowledge on MAIT cell biology in health and disease, and discuss the possible mechanisms behind their role in MS. The specific features of this new non-conventional T cell subset make it an interesting candidate as a biomarker or as the target of immune-mediated intervention.