Bacterial CD1d-restricted glycolipids induce IL-10 production by human regulatory T cells upon cross-talk with invariant NKT cells

Tregs protect against invariant NKT cell-mediated autoimmune colitis and hepatitis

Immunomodulatory T cells play a pivotal role in protection against (auto)immune-mediated diseases that open perspectives for therapeutic modulation. However, how immune regulatory networks operate in vivo is less understood. To this end, we focused on FOXP3+CD4+CD25+ regulatory T cells (Tregs) and invariant natural killer T (iNKT) cells, two lymphocyte populations that independently regulate adaptive and innate immune responses. In vitro, a functional interplay between Tregs and iNKT cells has been described, but whether Tregs modulate the function and phenotype of iNKT cell subsets in vivo and whether this controls iNKT-mediated autoimmunity is unclear. Taking advantage of the conditional depletion of Tregs, we examined the in vivo interplay between iNKT and Treg cells in steady state and in preclinical models of liver and gut autoimmunity. Under non-inflamed conditions, Treg depletion enhanced glycolipid-mediated iNKT cell responses, with a general impact on Type 1, 2 and 17 iNKT subsets. Moreover, in vivo iNKT activation in the absence of Tregs suppressed the induction of iNKT anergy, consistent with a reduction in programmed cell death receptor 1 (PD-1) expression. Importantly, we unveiled a clear role for an in vivo Treg-iNKT crosstalk both in concanavalin A-induced acute hepatitis and oxazolone-induced colitis. Here, the absence of Tregs led to a markedly enhanced liver and gut pathology, which was not observed in iNKT-deficient mice. Taken together, these results provide evidence for a functional interplay between regulatory T cell subsets critical in controlling the onset of autoimmune disease.

Role of CD1d and iNKT cells in regulating intestinal inflammation

Invariant natural killer T (iNKT) cells, a subset of unconventional T cells that recognize glycolipid antigens in a CD1d-dependent manner, are crucial in regulating diverse immune responses such as autoimmunity. By engaging with CD1d-expressing non-immune cells (such as intestinal epithelial cells and enterochromaffin cells) and immune cells (such as type 3 innate lymphoid cells, B cells, monocytes and macrophages), iNKT cells contribute to the maintenance of immune homeostasis in the intestine. In this review, we discuss the impact of iNKT cells and CD1d in the regulation of intestinal inflammation, examining both cellular and molecular factors with the potential to influence the functions of iNKT cells in inflammatory bowel diseases such as Crohn's disease and ulcerative colitis.

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

First-in-human clinical trial of the NKT cell-stimulatory glycolipid OCH in multiple sclerosis

Background

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system that causes the damage to the myelin sheath as well as axonal degeneration. Individuals with MS appear to have changes in the numbers and functions of T-cell subsets, leading to an immunological imbalance accompanied by enhanced autoreactivity. In previous preclinical studies, (2 S,3 S,4R)-1-O-(α-D-Galactopyranosyl)-N-tetracosanoyl-2-amino-1,3,4-nonanetriol (OCH), a synthetic analog of α-galactosylceramide stimulatory for invariant NKT (iNKT) cells, has shown therapeutic or disease-preventive immunoregulatory effects in autoimmune disease models such as experimental autoimmune encephalomyelitis (EAE).

Objectives

This study is the first-in-human study of oral OCH to evaluate the pharmacokinetics and to examine the effects on immune cells as well as related gene expression profiles.

Methods

Fifteen healthy volunteers and 13 MS patients who met the study criteria were enrolled. They were divided into five cohorts and received oral administration of various doses of granulated powder of OCH (0.3-30 mg), once per week for 4 or 13 weeks. Plasma OCH concentrations were measured by high-performance liquid chromatography. Frequencies of lymphocyte subsets in peripheral blood were evaluated by flow cytometry, and microarray analysis was performed to determine OCH-induced changes in gene expression.

Results

Oral OCH was well tolerated, and its bioavailability was found to be sufficient. Six hours after a single dose of OCH, increased frequencies of Foxp3⁺ regulatory T-cells were observed in some cohorts of healthy subjects and MS patients. Furthermore, gene expression analysis demonstrated an upregulation of several immunoregulatory genes and downregulation of pro-inflammatory genes following OCH administration.

Conclusion

This study has demonstrated immunomodulatory effects of the iNKT cell-stimulatory drug OCH in human. Safety profiles together with the presumed anti-inflammatory effects of oral OCH encouraged us to conduct a phase II trial.

Regulatory T Cells: Angels or Demons in the Pathophysiology of Sepsis?

Sepsis is a syndrome characterized by life-threatening organ dysfunction caused by the dysregulated host response to an infection. Sepsis, especially septic shock and multiple organ dysfunction is a medical emergency associated with high morbidity, high mortality, and prolonged after-effects. Over the past 20 years, regulatory T cells (Tregs) have been a key topic of focus in all stages of sepsis research. Tregs play a controversial role in sepsis based on their heterogeneous characteristics, complex organ/tissue-specific patterns in the host, the multi-dimensional heterogeneous syndrome of sepsis, the different types of pathogenic microbiology, and even different types of laboratory research models and clinical research methods. In the context of sepsis, Tregs may be considered both angels and demons. We propose that the symptoms and signs of sepsis can be attenuated by regulating Tregs. This review summarizes the controversial roles and Treg checkpoints in sepsis.

Harnessing invariant natural killer T cells to control pathological inflammation

Invariant natural killer T (iNKT) cells are innate T cells that are recognized for their potent immune modulatory functions. Over the last three decades, research in murine models and human observational studies have revealed that iNKT cells can act to limit inflammatory pathology in a variety of settings. Since iNKT cells are multi-functional and can promote inflammation in some contexts, understanding the mechanistic basis for their anti-inflammatory effects is critical for effectively harnessing them for clinical use. Two contrasting mechanisms have emerged to explain the anti-inflammatory activity of iNKT cells: that they drive suppressive pathways mediated by other regulatory cells, and that they may cytolytically eliminate antigen presenting cells that promote excessive inflammatory responses. How these activities are controlled and separated from their pro-inflammatory functions remains a central question. Murine iNKT cells can be divided into four functional lineages that have either pro-inflammatory (NKT1, NKT17) or anti-inflammatory (NKT2, NKT10) cytokine profiles. However, in humans these subsets are not clearly evident, and instead most iNKT cells that are CD4⁺ appear oriented towards polyfunctional (T_H0) cytokine production, while CD4^- iNKT cells appear more predisposed towards cytolytic activity. Additionally, structurally distinct antigens have been shown to induce T_H1- or T_H2-biased responses by iNKT cells in murine models, but human iNKT cells may respond to differing levels of TCR stimulation in a way that does not neatly separate T_H1 and T_H2 cytokine production. We discuss the implications of these differences for translational efforts focused on the anti-inflammatory activity of iNKT cells.

Repeated α-GalCer Administration Induces a Type 2 Cytokine-Biased iNKT Cell Response and Exacerbates Atopic Skin Inflammation in Vα14Tg NC/Nga Mice

We have previously shown that Vα14 TCR Tg (Vα14^Tg) NC/Nga (NC) mice contain increased numbers of double-negative (DN) invariant natural killer T (iNKT) cells that protect against spontaneous development of atopic dermatitis (AD). iNKT cells can regulate immune responses by producing various cytokines such as IFNγ and IL4 rapidly upon stimulation with α-galactosylceramide (α-GalCer), a prototypical iNKT cell agonist. However, the precise role of α-GalCer-activated iNKT cells in AD development remains unclear. Therefore, we examined whether repeated activation of iNKT cells with α-GalCer can regulate the pathogenesis of AD in Vα14^Tg NC mice. We found that Vα14^Tg NC mice injected repeatedly with α-GalCer display exacerbated AD symptoms (e.g., a higher clinical score, IgE hyperproduction, and increased numbers of splenic mast cells and neutrophils) compared with vehicle-injected Vα14^Tg NC mice. Moreover, the severity of AD pathogenesis in α-GalCer-injected Vα14^Tg NC mice correlated with increased Th2 cells but reduced Th1 and Foxp3⁺ Treg cells. Furthermore, the resulting alterations in the Th1/Th2 and Treg/Th2 balance were strongly associated with a biased expansion of type 2 cytokine-deviated iNKT cells in α-GalCer-treated Vα14^Tg NC mice. Collectively, our results have demonstrated the adverse effect of repeated α-GalCer treatment on skin inflammation mediated by type 2 immunity.

Regulation and Functions of Protumoral Unconventional T Cells in Solid Tumors

The vast majority of studies on T cell biology in tumor immunity have focused on peptide-reactive conventional T cells that are restricted to polymorphic major histocompatibility complex molecules. However, emerging evidence indicated that unconventional T cells, including γδ T cells, natural killer T (NKT) cells and mucosal-associated invariant T (MAIT) cells are also involved in tumor immunity. Unconventional T cells span the innate-adaptive continuum and possess the unique ability to rapidly react to nonpeptide antigens via their conserved T cell receptors (TCRs) and/or to activating cytokines to orchestrate many aspects of the immune response. Since unconventional T cell lineages comprise discrete functional subsets, they can mediate both anti- and protumoral activities. Here, we review the current understanding of the functions and regulatory mechanisms of protumoral unconventional T cell subsets in the tumor environment. We also discuss the therapeutic potential of these deleterious subsets in solid cancers and why further feasibility studies are warranted.

Expansion of Human iNKT Cells Ex Vivo

Invariant natural killer T (iNKT) cells are credited with antitumor activity by preclinical studies and clinical trials. Efficient expansion of iNKT cells ex vivo is essential for their translational usage. The culturing procedure described here provides an optimized method for ex vivo expansion of iNKT cells using recombinant human IL-15 (rhIL-15) and recombinant human IL-12 (rhIL-12), which results in cell products with enhanced cytokine secretion and cytotoxicity while maintaining the purity and viability of iNKT cells.

ER stress in antigen-presenting cells promotes NKT cell activation through endogenous neutral lipids

CD1d‐restricted invariant natural killer T (iNKT) cells constitute a common glycolipid‐reactive innate‐like T‐cell subset with a broad impact on innate and adaptive immunity. While several microbial glycolipids are known to activate iNKT cells, the cellular mechanisms leading to endogenous CD1d‐dependent glycolipid responses remain largely unclear. Here, we show that endoplasmic reticulum (ER) stress in APCs is a potent inducer of CD1d‐dependent iNKT cell autoreactivity. This pathway relies on the presence of two transducers of the unfolded protein response: inositol‐requiring enzyme‐1a (IRE1α) and protein kinase R‐like ER kinase (PERK). Surprisingly, the neutral but not the polar lipids generated within APCs undergoing ER stress are capable of activating iNKT cells. These data reveal that ER stress is an important mechanism to elicit endogenous CD1d‐restricted iNKT cell responses through induction of distinct classes of neutral lipids.

Activation of immunosuppressive network in the aging process

Chronic low-grade inflammation has a key role in the aging process, a state called inflammaging. It is known that the chronic inflammatory condition generates counteracting immunosuppressive state in many diseases. Inflammaging is also associated with an immune deficiency; generally termed as immunosenescence, although it is not known whether it represents the senescence of immune cells or the active remodeling of immune system. Evidence has accumulated since the 1970's indicating that immunosenescence might be caused by an increased activity of immunosuppressive cells rather than cellular senescence. Immune cells display remarkable plasticity; many of these cells can express both proinflammatory and immunosuppressive phenotypes in a context-dependent manner. The immunosuppressive network involves the regulatory subtypes of T (Treg) and B (Breg) cells as well as regulatory phenotypes of macrophages (Mreg), dendritic (DCreg), natural killer (NKreg), and type II natural killer T (NKT) cells. The immunosuppressive network also includes monocytic (M-MDSC) and polymorphonuclear (PMN-MDSC) myeloid-derived suppressor cells which are immature myeloid cells induced by inflammatory mediators. This co-operative network is stimulated in chronic inflammatory conditions preventing excessive inflammatory responses but at the same time they exert harmful effects on the immune system and tissue homeostasis. Recent studies have revealed that the aging process is associated with the activation of immunosuppressive network, especially the functions of MDSCs, Tregs, and Mregs are increased. I will briefly review the properties of the regulatory phenotypes of immune cells and examine in detail the evidences for an activation of immunosuppressive network with aging.

RORγt inhibition selectively targets IL-17 producing iNKT and γδ-T cells enriched in Spondyloarthritis patients

Dysregulated IL-23/IL-17 responses have been linked to psoriatic arthritis and other forms of spondyloarthritides (SpA). RORγt, the key Thelper17 (Th17) cell transcriptional regulator, is also expressed by subsets of innate-like T cells, including invariant natural killer T (iNKT) and γδ-T cells, but their contribution to SpA is still unclear. Here we describe the presence of particular RORγt⁺T-bet^loPLZF^- iNKT and γδ-hi T cell subsets in healthy peripheral blood. RORγt⁺ iNKT and γδ-hi T cells show IL-23 mediated Th17-like immune responses and were clearly enriched within inflamed joints of SpA patients where they act as major IL-17 secretors. SpA derived iNKT and γδ-T cells showed unique and Th17-skewed phenotype and gene expression profiles. Strikingly, RORγt inhibition blocked γδ17 and iNKT17 cell function while selectively sparing IL-22⁺ subsets. Overall, our findings highlight a unique diversity of human RORγt⁺ T cells and underscore the potential of RORγt antagonism to modulate aberrant type 17 responses.

α-galactosylceramide generates lung regulatory T cells through the activated natural killer T cells in mice

Our previous study showed that intraperitoneal injection of α-galactosylceramide (α-GalCer) has the ability to activate lung iNKT cells, but α-GalCer-activated iNKT cells do not result in airway inflammation in wild-type (WT) mice. Many studies showed that iNKT cells had the capacity to induce Treg cells, which gave rise to peripheral tolerance. Therefore, we examined the influence of intraperitoneal administration of α-GalCer on the expansion and suppressive activity of lung Treg cells using iNKT cell-knockout mice and co-culture experiments in vitro. We also compared airway inflammation and airway hyperresponsiveness (AHR) after α-GalCer administration in specific anti-CD25 mAb-treated mice. Our data showed that intraperitoneal injection of α-GalCer could promote the expansion of lung Treg cells in WT mice, but not in iNKT cell-knockout mice. However, α-GalCer administration could not boost suppressive activity of Treg cells in WT mice and iNKT cell-knockout mice. Interestingly, functional inactivation of Treg cells could induce airway inflammation and AHR in WT mice treated with α-GalCer. Furthermore, α-GalCer administration could enhance iNKT cells to secrete IL-2, and neutralization of IL-2 reduced the expansion of Treg cells in vivo and in vitro. Thus, intraperitoneal administration of α-GalCer can induce the generation of lung Treg cells in mice through the release of IL-2 by the activated iNKT cells.

The Impact of Invariant NKT Cells in Sterile Inflammation: The Possible Contribution of the Alarmin/Cytokine IL-33

Although the contribution of iNKT cells to induction of sterile inflammation is now well-established, the nature of the endogenous compounds released early after cellular stress or damage that drive their activation and recruitment remains poorly understood. More precisely, iNKT cells have not been described as being reactive to endogenous non-protein damage-associated molecular-pattern molecules (DAMPs). A second subset of DAMPs, called alarmins, are tissue-derived nuclear proteins, constitutively expressed at high levels in epithelial barrier tissues and endothelial barriers. These potent immunostimulants, immediately released after tissue damage, include the alarmin IL-33. This factor has aroused interest due to its singular action as an alarmin during infectious, allergic responses and acute tissue injury, and as a cytokine, contributing to the latter resolutive/repair phase of sterile inflammation. IL-33 targets iNKT cells, inducing their recruitment in an inflammatory state, and amplifying their regulatory and effector functions. In the present review, we introduce the new concept of a biological axis of iNKT cells and IL-33, involved in alerting and controlling the immune cells in experimental models of sterile inflammation. This review will focus on acute organ injury models, especially ischemia-reperfusion injury, in the kidneys, liver and lungs, where iNKT cells and IL-33 have been presumed to mediate and/or control the injury mechanisms, and their potential relevance in human pathophysiology.

Tissue-Specific Roles of NKT Cells in Tumor Immunity

NKT cells are an unusual population of T cells recognizing lipids presented by CD1d, a non-classical class-I-like molecule, rather than peptides presented by conventional MHC molecules. Type I NKT cells use a semi-invariant T cell receptor and almost all recognize a common prototype lipid, α-galactosylceramide (α-GalCer). Type II NKT cells are any lipid-specific CD1d-restricted T cells that use other receptors and generally don't recognize α-GalCer. They play important regulatory roles in immunity, including tumor immunity. In contrast to type I NKT cells that most have found to promote antitumor immunity, type II NKT cells suppress tumor immunity and the two subsets cross-regulate each other, forming an immunoregulatory axis. They also can promote other regulatory cells including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), and can induce MDSCs to secrete TGF-β, one of the most immunosuppressive cytokines known. In some tumors, both Tregs and type II NKT cells can suppress immunosurveillance, and the balance between these is determined by a type I NKT cell. We have also seen that regulation of tumor immunity can depend on the tissue microenvironment, so the same tumor in the same animal in different tissues may be regulated by different cells, such as type II NKT cells in the lung vs Tregs in the skin. Also, the effector T cells that protect those sites when Tregs are removed do not always act between tissues even in the same animal. Thus, metastases may require different immunotherapy from primary tumors. Newly improved sulfatide-CD1d tetramers are starting to allow better characterization of the elusive type II NKT cells to better understand their function and control it to overcome immunosuppression.

iNKT cells ameliorate human autoimmunity: Lessons from alopecia areata

Alopecia areata (AA) is understood to be a CD8+/NKG2D+ T cell-dependent autoimmune disease. Here, we demonstrate that human AA pathogenesis of is also affected by iNKT10 cells, an unconventional T cell subtype whose number is significantly increased in AA compared to healthy human skin. AA lesions can be rapidly induced in healthy human scalp skin xenotransplants on Beige-SCID mice by intradermal injections of autologous healthy-donor PBMCs pre-activated with IL-2. We show that in this in vivo model, the development of AA lesions is prevented by recognized the iNKT cell activator, α-galactosylceramide (α-GalCer), which stimulates iNKT cells to expand and produce IL-10. Moreover, in pre-established humanized mouse AA lesions, hair regrowth is promoted by α-GalCer treatment through a process requiring both effector-memory iNKT cells, which can interact directly with CD8+/NKG2D+ T cells, and IL-10. This provides the first in vivo evidence in a humanized model of autoimmune disease that iNKT10 cells are key disease-protective lymphocytes. Since these regulatory NKT cells can both prevent the development of AA lesions and promote hair re-growth in established AA lesions, targeting iNKT10 cells may have preventive and therapeutic potential also in other autoimmune disorders related to AA.

Does an NKT-cell-based immunotherapeutic approach have a future in multiple myeloma?

Natural killer T (NKT) cells constitute a unique subset of innate-like T lymphocytes which differ from conventional T cells by recognizing lipid antigens presented by the non-polymorphic major histocompatibility complex (MHC) I-like molecule CD1d. Despite being a relatively infrequent population of lymphocytes, NKT cells can respond rapidly upon activation with glycosphingolipids by production of cytokines which aim to polarize different axes of the immune system. Due to their dual effector capacities, NKT cells can play a vital role in cancer immunity, infection, inflammation and autoimmune diseases. It is believed that modulation of their activity towards immune activation can be a useful tool in anti-tumor immunotherapeutic strategies. Here we summarize the characteristics of NKT cells and discuss their involvement in immunosurveillance. Furthermore, an update is given about their role and the progress that has been made in the field of multiple myeloma (MM). Finally, some challenges are discussed that are currently hampering further progress.

Influenza A virus-induced release of interleukin-10 inhibits the anti-microbial activities of invariant natural killer T cells during invasive pneumococcal superinfection

During influenza A virus (IAV) infection, changes in the lung's physical and immunological defenses predispose the host to bacterial superinfections. Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that have beneficial or harmful functions during infection. We investigated the iNKT cells' role in a model of invasive pneumococcal superinfection. The use of Jα18^-/- mice indicated that iNKT cells limited susceptibility to influenza-pneumococcal infection and reduced the lethal synergism. This role did not depend on immune-based anti-bacterial mechanisms. At the time of bacterial exposure, iNKT cells from IAV-experienced mice failed to produce antipneumococcal interferon-γ and adoptive transfer of fresh iNKT cells before Streptococcus pneumoniae challenge did not restore anti-bacterial host defenses. Impaired iNKT cell activation in superinfected animals was related to the IAV-induced immunosuppressive cytokine interleukin-10 (IL-10), rather than to an intrinsic functional defect. IL-10 dampened the activation of iNKT cells in response to pneumococci by inhibiting the production of IL-12 by pulmonary monocyte-derived dendritic cells. Neutralization of IL-10 restored iNKT cell activation and tends to increase resistance to secondary bacterial infection. Overall, iNKT cells have a beneficial role (upstream of bacterial colonization) in controlling influenza-pneumococcal superinfection, although they represent novel targets of immunosuppression at the time of bacterial challenge.

NKT cells mediate the recruitment of neutrophils by stimulating epithelial chemokine secretion during colitis

Ulcerative colitis (UC) is a kind of inflammatory bowel diseases characterized by chronic inflammation and ulcer in colon, and UC patients have increased risk of getting colorectal cancer. NKT cells are cells that express both NK cell markers and semi-invariant CD1d-restricted TCRs, can regulate immune responses via secreting a variety of cytokines upon activation. In our research, we found that the NKT cell-deficient CD1d(-/-) mice had relieved colitis in the DSS-induced colitis model. Further investigations revealed that the colon of CD1d(-/-) mice expressed less neutrophil-attracting chemokine CXCL 1, 2 and 3, and had decreased neutrophil infiltration. Infiltrated neutrophils also produced less reactive oxygen species (ROS) and TNF-α, indicating they may cause less epithelial damage. In addition, colitis-associated colorectal cancer was also relieved in CD1d(-/-) mice. During colitis, NKT cells strongly expressed TNF-α, which could stimulate CXCL 1, 2, 3 expressions by the epithelium. In conclusion, NKT cells can regulate colitis via the NKT cell-epithelium-neutrophil axis. Targeting this mechanism may help to improve the therapy of UC and prevent colitis-associated colorectal cancer.

Antitumor Responses of Invariant Natural Killer T Cells

Natural killer T (NKT) cells are innate-like lymphocytes that were first described in the late 1980s. Since their initial description, numerous studies have collectively shed light on their development and effector function. These studies have highlighted the unique requirements for the activation of these lymphocytes and the functional responses that distinguish these cells from other effector lymphocyte populations such as conventional T cells and NK cells. This body of literature suggests that NKT cells play diverse nonredundant roles in a number of disease processes, including the initiation and propagation of airway hyperreactivity, protection against a variety of pathogens, development of autoimmunity, and mediation of allograft responses. In this review, however, we focus on the role of a specific lineage of NKT cells in antitumor immunity. Specifically, we describe the development of invariant NKT (iNKT) cells and the factors that are critical for their acquisition of effector function. Next, we delineate the mechanisms by which iNKT cells influence and modulate the activity of other immune cells to directly or indirectly affect tumor growth. Finally, we review the successes and failures of clinical trials employing iNKT cell-based immunotherapies and explore the future prospects for the use of such strategies.

Dendritic cells and anergic type I NKT cells play a crucial role in sulfatide-mediated immune regulation in experimental autoimmune encephalomyelitis

CD1d-restricted NKT cells can be divided into two groups: type I NKT cells use a semi-invariant TCR, whereas type II express a relatively diverse set of TCRs. A major subset of type II NKT cells recognizes myelin-derived sulfatides and is selectively enriched in the CNS tissue during experimental autoimmune encephalomyelitis (EAE). We have shown that activation of sulfatide-reactive type II NKT cells by sulfatide prevents induction of EAE. In this article, we have addressed the mechanism of regulation, as well as whether a single immunodominant form of synthetic sulfatide can treat ongoing chronic and relapsing EAE in SJL/J mice. We have shown that the activation of sulfatide-reactive type II NKT cells leads to a significant reduction in the frequency and effector function of myelin proteolipid proteins 139-151/I-A(s)-tetramer(+) cells in lymphoid and CNS tissues. In addition, type I NKT cells and dendritic cells (DCs) in the periphery, as well as CNS-resident microglia, are inactivated after sulfatide administration, and mice deficient in type I NKT cells are not protected from disease. Moreover, tolerized DCs from sulfatide-treated animals can adoptively transfer protection into naive mice. Treatment of SJL/J mice with a synthetic cis-tetracosenoyl sulfatide, but not α-galactosylceramide, reverses ongoing chronic and relapsing EAE. Our data highlight a novel immune-regulatory pathway involving NKT subset interactions leading to inactivation of type I NKT cells, DCs, and microglial cells in suppression of autoimmunity. Because CD1 molecules are nonpolymorphic, the sulfatide-mediated immune-regulatory pathway can be targeted for development of non-HLA-dependent therapeutic approaches to T cell-mediated autoimmune diseases.

Adding glycolipid functionality to model membranes--phase behaviour of a synthetic glycolipid in a phospholipid membrane

Glycolipid phase behaviour is less well understood than for many phospholipids, but due to their structural and functional diversity, glycolipids represent an important group of amphiphiles from which biological function is derived. Here we have incorporated a synthetic glycolipid in binary mixtures with DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) into giant unilamellar vesicles (GUVs) at biologically relevant concentrations and observed the phase behaviour of the lipid mixtures for a range of glycolipid concentrations. At low concentrations, the glycolipid is fully dispersed in the GUV membrane. At glycolipid molar concentrations above 10%, the formation of lipid tubules is observed, and is consistent with the formation of a columnar lipid phase. Lipid tubules are observed in aqueous and oil solvents, suggesting that both hexagonal and inverted hexagonal lipid arrangements can be formed. This work may offer insights into the biological function of glycolipids and the challenges in formulating them for use in industrial applications.

The immunoregulatory role of type I and type II NKT cells in cancer and other diseases

NKT cells are CD1d-restricted T cells that recognize lipid antigens. They also have been shown to play critical roles in the regulation of immune responses. In the immune responses against tumors, two subsets of NKT cells, type I and type II, play opposing roles and cross-regulate each other. As members of both the innate and adaptive immune systems, which form a network of multiple components, they also interact with other immune components. Here, we discuss the function of NKT cells in tumor immunity and their interaction with other regulatory cells, especially CD4(+)CD25(+)Foxp3(+) regulatory T cells.