[Show abstract][Hide abstract] ABSTRACT: Invariant natural killer T (iNKT) cells are a unique population of lipid-reactive CD1d-restricted innate-like T lymphocytes. Despite being a minor population, they serve as an early source of cytokines and promote immunological crosstalk thus bridging innate and adaptive immunity. Diseases ranging from allergy, autoimmunity, and cancer, as well as infectious diseases, including viral infection, have been reported to be influenced by iNKT cells. However, it remains unclear how iNKT cells are activated during viral infection, as virus-derived lipid antigens have not been reported. Cytokines may activate iNKT cells during infections from influenza and murine cytomegalovirus, although CD1d-dependent activation is evident in other viral infections. Several viruses, such as dengue virus, induce CD1d upregulation, which correlates with iNKT cell activation. In contrast, herpes simplex virus type 1 (HSV-1), human immunodeficiency virus (HIV), Epstein-Barr virus, and human papilloma virus promote CD1d downregulation as a strategy to evade iNKT cell recognition. These observations suggest the participation of a CD1d-dependent process in the activation of iNKT cells in response to viral infection. Endogenous lipid ligands, including phospholipids as well as glycosphingolipids, such as glucosylceramide, have been proposed to mediate iNKT cell activation. Pro-inflammatory signals produced during viral infection may stimulate iNKT cells through enhanced CD1d-dependent endogenous lipid presentation. Furthermore, viral infection may alter lipid composition and inhibit endogenous lipid degradation. Recent advances in this field are reviewed.
Frontiers in Immunology 01/2015; 6:378. DOI:10.3389/fimmu.2015.00378
[Show abstract][Hide abstract] ABSTRACT: Background
Dengue viral infection is a global health threat without vaccine or specific treatment. The clinical outcome varies from asymptomatic, mild dengue fever (DF) to severe dengue hemorrhagic fever (DHF). While adaptive immune responses were found to be detrimental in the dengue pathogenesis, the roles of earlier innate events remain largely uninvestigated. Invariant natural killer T (iNKT) cells represent innate-like T cells that could dictate subsequent adaptive response but their role in human dengue virus infection is not known. We hypothesized that iNKT cells play a role in human dengue infection.
Blood samples from a well-characterized cohort of children with DF, DHF, in comparison to non-dengue febrile illness (OFI) and healthy controls at various time points were studied. iNKT cells activation were analyzed by the expression of CD69 by flow cytometry. Their cytokine production was then analyzed after α-GalCer stimulation. Further, the CD1d expression on monocytes, and CD69 expression on conventional T cells were measured.
iNKT cells were activated during acute dengue infection. The level of iNKT cell activation associates with the disease severity. Furthermore, these iNKT cells had altered functional response to subsequent ex vivo stimulation with α-GalCer. Moreover, during acute dengue infection, monocytic CD1d expression was also upregulated and conventional T cells also became activated.
iNKT cells might play an early and critical role in the pathogenesis of severe dengue viral infection in human. Targeting iNKT cells and CD1d serve as a potential therapeutic strategy for severe dengue infection in the future.
[Show abstract][Hide abstract] ABSTRACT: Immune cells called mast cells can hinder rather than help the body's response to dengue virus, which suggests that mast cell products could be used as biomarkers to identify severe forms of the disease.
[Show abstract][Hide abstract] ABSTRACT: Asthma has been considered an immunologic disease mediated by T(H)2 cells and adaptive immunity. However, clinical and experimental observations suggest that additional pathways might regulate asthma, particularly in its nonallergic forms, such as asthma associated with air pollution, stress, obesity, and infection.
Our goal was to understand T(H)2 cell-independent conditions that might lead to airway hyperreactivity (AHR), a cardinal feature of asthma.
We examined a murine model of experimental asthma in which AHR was induced with glycolipid antigens, which activate natural killer T (NKT) cells.
In this model AHR developed rapidly when mice were treated with NKT cell-activating glycolipid antigens, even in the absence of conventional CD4(+) T cells. The activated NKT cells directly induced alveolar macrophages to produce IL-33, which in turn activated NKT cells, as well as natural helper cells, a newly described non-T, non-B, innate lymphoid cell type, to increase production of IL-13. Surprisingly, this glycolipid-induced AHR pathway required not only IL-13 but also IL-33 and its receptor, ST2, because it was blocked by an anti-ST2 mAb and was greatly reduced in ST2(-/-) mice. When adoptively transferred into IL-13(-/-) mice, both wild-type natural helper cells and NKT cells were sufficient for the development of glycolipid-induced AHR.
Because plant pollens, house dust, and some bacteria contain glycolipids that can directly activate NKT cells, these studies suggest that AHR and asthma can fully develop or be greatly enhanced through innate immune mechanisms involving IL-33, natural helper cells, and NKT cells.
The Journal of allergy and clinical immunology 11/2011; 129(1):216-27.e1-6. DOI:10.1016/j.jaci.2011.10.036 · 11.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: During infection with the hepatitis A virus (HAV), most patients develop mild or asymptomatic disease. However, a small number of patients develop serious, life-threatening hepatitis. We investigated this variability in disease severity by examining 30 Argentinean patients with HAV-induced acute liver failure in a case-control, cross-sectional, observational study. We found that HAV-induced severe liver disease was associated with a 6-amino-acid insertion in TIM1/HAVCR1 (157insMTTTVP), the gene encoding the HAV receptor. This polymorphism was previously shown to be associated with protection against asthma and allergic diseases and with HIV progression. In binding assays, the TIM-1 protein containing the 157insMTTTVP insertion polymorphism bound HAV more efficiently. When expressed by human natural killer T (NKT) cells, this long form resulted in greater NKT cell cytolytic activity against HAV-infected liver cells, compared with the shorter TIM-1 protein without the polymorphism. To our knowledge, the 157insMTTTVP polymorphism in TIM1 is the first genetic susceptibility factor shown to predispose to HAV-induced acute liver failure. Furthermore, these results suggest that HAV infection has driven the natural selection of shorter forms of the TIM-1 protein, which binds HAV less efficiently, thereby protecting against severe HAV-induced disease, but which may predispose toward inflammation associated with asthma and allergy.
The Journal of clinical investigation 02/2011; 121(3):1111-8. DOI:10.1172/JCI44182 · 13.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A crucial role has been suggested for invariant natural killer T cells (iNKT) in regulating the development of asthma, a complex and heterogeneous disease characterized by airway inflammation and airway hyperreactivity (AHR). iNKT cells constitute a unique subset of T cells responding to endogenous and exogenous lipid antigens, rapidly secreting a large amount of cytokines, which amplify both innate and adaptive immunity. Herein, we review recent studies showing a requirement for iNKT cells in various models of asthma in mice and monkeys as well as studies in human patients. Surprisingly, in several different murine models of asthma, distinct subsets of iNKT cells were required, suggesting that iNKT cells serve as a common critical pathogenic element for many different forms of asthma. The importance of iNKT cells in both allergic and non-allergic forms of asthma, which are independent of adaptive immunity and associated with airway neutrophils, may explain situations previously found to be incompatible with the Th2 paradigm of asthma.
[Show abstract][Hide abstract] ABSTRACT: Studies in mice, monkeys and humans suggest that invariant natural killer (iNK) T cells play a very important role in the pathogenesis of asthma, a heterogeneous disease associated with airway inflammation and airway hyper-reactivity. The requirement for iNK T cells in multiple mouse models of asthma is novel and surprising, challenging the prevailing dogma that CD4(+) T cells responding to environmental allergens are the key cell type in asthma. In this article, we examine the recent studies of iNK T cells and asthma, and discuss how different subsets of NK T cells function in different forms of asthma, including forms that are independent of adaptive immunity and Th2 cells. Together, these studies suggest that iNK T cells, which can interact with many other cell types including Th2 cells, eosinophils and neutrophils, provide a unifying pathogenic mechanism for many distinct forms of asthma.
[Show abstract][Hide abstract] ABSTRACT: T-bet(-/-) mice have been shown to have a profound deficiency in the ability to generate invariant NKT (iNKT) cells in the periphery due to a halt in terminal maturation, but despite this deficiency, T-bet(-/-) mice develop spontaneous airway hyperreactivity (AHR) and airway inflammation. Because in some situations the development of AHR requires the presence of iNKT cells, we sought to more clearly understand how AHR develops in T-bet(-/-) mice by examining T-bet(-/-) mice in several distinct mouse models of asthma, including spontaneous, OVA-induced and alpha-galactosylceramide (alpha-GalCer)-induced AHR. Surprisingly, we found that administration of alpha-GalCer, which very specifically activates iNKT cells, greatly increased the AHR response in the T-bet(-/-) mice. Moreover, in T-bet(-/-) mice, spontaneous AHR as well as AHR induced with OVA or alpha-GalCer were all eliminated by blocking CD1d, the restricting element of iNKT cells, using an anti-CD1d-blocking mAb. Although the number of the iNKT cells in T-bet(-/-) mice was reduced compared with that in wild-type mice, the remaining iNKT cells produced primarily IL-4 and IL-13, and only minimal amounts of IFN-gamma. We conclude therefore that the AHR that develops in T-bet(-/-) mice is dependent on the presence of iNKT cells, and that whereas T-bet(-/-) have reduced numbers of iNKT cells, these are sufficient for the development of AHR.
The Journal of Immunology 04/2009; 182(5):3252-61. DOI:10.4049/jimmunol.0803339 · 5.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exposure to ozone, which is a major component of air pollution, induces a form of asthma that occurs in the absence of adaptive immunity. Although ozone-induced asthma is characterized by airway neutrophilia, and not eosinophilia, it is nevertheless associated with airway hyperreactivity (AHR), which is a cardinal feature of asthma. Because AHR induced by allergens requires the presence of natural killer T (NKT) cells, we asked whether ozone-induced AHR had similar requirements. We found that repeated exposure of wild-type (WT) mice to ozone induced severe AHR associated with an increase in airway NKT cells, neutrophils, and macrophages. Surprisingly, NKT cell-deficient (CD1d(-/-) and Jalpha18(-/-)) mice failed to develop ozone-induced AHR. Further, treatment of WT mice with an anti-CD1d mAb blocked NKT cell activation and prevented ozone-induced AHR. Moreover, ozone-induced, but not allergen-induced, AHR was associated with NKT cells producing interleukin (IL)-17, and failed to occur in IL-17(-/-) mice nor in WT mice treated with anti-IL-17 mAb. Thus, ozone exposure induces AHR that requires the presence of NKT cells and IL-17 production. Because NKT cells are required for the development of two very disparate forms of AHR (ozone- and allergen-induced), our results strongly suggest that NKT cells mediate a unifying pathogenic mechanism for several distinct forms of asthma, and represent a unique target for effective asthma therapy.
Journal of Experimental Medicine 03/2008; 205(2):385-93. DOI:10.1084/jem.20071507 · 13.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hypomorphic mutations of the RAG genes in humans are associated with a spectrum of clinical and immunologic presentations that range from T(-) B(-) severe combined immune deficiency (SCID) to Omenn syndrome. In most cases, residual V(D)J recombination activity allows for development of few T-cell clones, which expand in the periphery and infiltrate target organs, resulting in tissue damage. Invariant natural killer T (iNKT) cells play an important immunoregulatory role and have been associated with protection against autoimmunity. We now report on 5 unrelated cases of combined immune deficiency due to hypomorphic RAG mutations, and demonstrate the absence of iNKT cells in all 5 patients. These findings suggest that lack of this important immunoregulatory cell population may contribute to the pathophysiology of Omenn syndrome.