The natural killer T-cell ligand alpha-galactosylceramide prevents autoimmune diabetes in non-obese diabetic mice

Selective loss of innate CD4(+) V alpha 24 natural killer T cells in human immunodeficiency virus infection

V alpha 24 natural killer T (NKT) cells are innate immune cells involved in regulation of immune tolerance, autoimmunity, and tumor immunity. However, the effect of human immunodeficiency virus type 1 (HIV-1) infection on these cells is unknown. Here, we report that the V alpha 24 NKT cells can be subdivided into CD4(+) or CD4(-) subsets that differ in their expression of the homing receptors CD62L and CD11a. Furthermore, both CD4(+) and CD4(-) NKT cells frequently express both CXCR4 and CCR5 HIV coreceptors. We find that the numbers of NKT cells are reduced in HIV-infected subjects with uncontrolled viremia and marked CD4(+) T-cell depletion. The number of CD4(+) NKT cells is inversely correlated with HIV load, indicating depletion of this subset. In contrast, CD4(-) NKT-cell numbers are unaffected in subjects with high viral loads. HIV infection experiments in vitro show preferential depletion of CD4(+) NKT cells relative to regular CD4(+) T cells, in particular with virus that uses the CCR5 coreceptor. Thus, HIV infection causes a selective loss of CD4(+) lymph node homing (CD62L(+)) NKT cells, with consequent skewing of the NKT-cell compartment to a predominantly CD4(-) CD62L(-) phenotype. These data indicate that the key immunoregulatory NKT-cell compartment is compromised in HIV-1-infected patients.

Role of NKT cells and alpha-galactosyl ceramide

Alfa-Galactosyl Ceramide was isolated from Ocean sponge which has antitumor effect against several tumors in in vivo animal model with no cytotoxicity. KRN7000(KRN) is the most potent alpha-Galactosyl Ceramide modified from the one isolated from Ocean sponge. KRN is also active against metastatic tumors through the activation ofanimal immune system. Research efforts in learning the mechanism of action, we found the important role of dendritic cells(DC) and NKT cells. NKT cells was first characterized in 1988 which is overlap some part with NK cells and T-Cells and majority is different from NK and T. KRN is active through the activation of DC and NKT in giving antigen specific immune stimulation in animal. This antigen specific stimulation is memorized by immune system and can reject second tumor challenge. KRN is not active in nude mice and NKT deficient animal. NKT cells level in blood is lower in patients with autoimmune disease, cancer, HIV positive or aplastic anemia. NKT rapidly releases IL-4 and IFN-gamma at high level when activated. NKT is CD1d and TCR restricted. NKT plays important role in autoimmune disease such as Type 1 Diabetes, Scleroderma and Systemic Lupus Erythematosus, infections such as Mycobacteria, Listeria and Malaria, GVHD control and tumor rejection. NKT acts as double edge sword, aggressive and suppressive ways. KRN can prevent the onset of Type 1 Diabetes, inhibit replication of hepatitis virus B in liver and suppress malaria replication in activating NKT cells. KRN can activate NKT through DC and activated NKT activates NK, T and macrophage. KRN also expands NKT cells and expanded NKT has full function. Although the exact role of DC and NKT is not clear, KRN clinical study results in conjunction with DC and NKT cell activation are expected.

Immune regulation in adjuvant disease and other arthritis models: relevance to pathogenesis of chronic arthritis

Experimental models of arthritis and their human counterparts fall into three distinct classes: (a) responses of T cells to disseminated microbial antigens (Ags) as such; (b) responses of T cells to cartilage autoAgs; and (c) responses of T cells to major histocompatibility complex (HLA-B27, DRB1) or other membrane components (LFA-1) expressed on bone marrow-derived cells. The primary immune response is driven, in naturally occurring disease, by microbial infection, e.g. with streptococci, enteric gram-negative rods or spirochetes, or is experimentally induced with mycobacterial and other adjuvants. The response to cartilage components, such as collagen type-II and various proteoglycans, may be driven by cross-reactive microbial Ags, heat shock proteins (HSPs) in particular, or the adjuvant effect of intense primary joint inflammation, as in rheumatoid arthritis and the spondyloarthropathies. Adjuvant disease appears to be purely T-cell-mediated, whereas both T cells and antibody play a role in collagen and many other forms of arthritis. Experimental evidence suggests a pathogenetic role for T-cell receptor gammadelta T cells in some lesions. Arthritis may be regulated by microbial and tissue HSPs, when these are administered by a nonimmunizing route or as altered peptide ligands, by anti-idiotypic responses that block the action of effector T cells, and by competing Ags. Immune regulation involving natural killer (NK), NK T and certain subsets of gammadelta and alphabeta T cells, which may affect the occurrence, localization and character of this group of diseases, presents a challenge for further investigation.

Synthesis of alpha-galactosyl ceramide, a potent immunostimulatory agent

Alpha-galactosyl ceramide has been identified to be a potent stimulatory agent for a novel immunological process, mediated by CD1 molecules. This paper describes a short and efficient synthesis of alpha-galactosyl ceramide. Starting from commercially available 2-deoxy galactose, a suitable sphingosine derivative was obtained in nine steps and 36% overall yield, which was subsequently glycosylated to give the target molecule. This flexible route will provide various glycolipids for further exploration of this interesting biological process.

Treatment with alpha-galactosylceramide before Trypanosoma cruzi infection provides protection or induces failure to thrive

Trypanosoma cruzi, a protozoan parasite, chronically infects many mammalian species and triggers a chronic inflammatory disease. Invariant Valpha14 NK T (iNKT) cells are a regulatory subset of T cells that can contribute to protection against pathogens and to control of chronic inflammatory diseases. alpha-Galactosylceramide (alpha-GalCer) is an iNKT cell-specific glycolipid Ag: a single immunization with alpha-GalCer stimulates robust IFN-gamma and IL-4 production by iNKT cells, while multiple immunizations stimulate IL-4 production, but limited IFN-gamma production. We recently demonstrated that iNKT cells help control T. cruzi infection and affect the chronic Ab response. Therefore, alpha-GalCer treatment might be used to increase protection or decrease chronic inflammation during T. cruzi infection. In this report, we show that a single dose of alpha-GalCer before T. cruzi infection decreases parasitemia. This protection is independent of IL-12, but dependent upon iNKT cell IFN-gamma. In addition, alpha-GalCer treatment of the IFN-gamma(-/-) mice exacerbates parasitemia through IL-4 production. Furthermore, a multiple dose regimen of alpha-GalCer before T. cruzi infection does not lower parasitemia and, surprisingly, after parasitemia has resolved, causes poor weight gain. These data demonstrate that during T. cruzi infection glycolipids can be used to manipulate iNKT cell responses and suggest the possibility of developing glycolipid treatments that can increase protection and possibly decrease the chronic inflammatory pathology.

Immunotherapy with ligands of natural killer T cells

Natural killer T (NKT) cells are innate lymphocytes that share receptor structures and functions with conventional T cells and natural killer cells. NKT cells are specific for glycolipid antigens bound by the major histocompatibility complex class I-like protein CD1d. One striking property of NKT cells is their capacity to rapidly produce large amounts of cytokines in response to T-cell receptor engagement, suggesting that activated NKT cells can modulate adaptive immune responses. Recent pre-clinical studies have revealed significant efficacy of NKT-cell ligands such as the glycolipid alpha-galactosylceramide for treatment of metastatic cancers and infections, and for prevention of autoimmune diseases. These findings suggest that appropriate stimulation of NKT cells could be exploited for prevention or treatment of human diseases.

NKT cells: potential targets for autoimmune disease therapy?

NKT cells represent a unique T cell lineage that recognize glycolipid antigens in the context of the non-classical MHC class I molecule CD1d. NKT cells are potent producers of immunoregulatory cytokines, and have been implicated in several different autoimmune diseases in mice and humans, including Type 1 diabetes, experimental autoimmune encephalomyelitis--a mouse model for multiple sclerosis, systemic lupus erythematosus, and scleroderma. This review will cover the evidence for an involvement for NKT cells in these autoimmune diseases, and discuss the potential for therapeutic manipulation of these cells as a means of preventing autoimmune disease in the clinic.

NK T cells contribute to expansion of CD8(+) T cells and amplification of antiviral immune responses to respiratory syncytial virus

CD1d-deficient mice have normal numbers of T lymphocytes and natural killer cells but lack Valpha14(+) natural killer T cells. Respiratory syncytial virus (RSV) immunopathogenesis was evaluated in 129xC57BL/6, C57BL/6, and BALB/c CD1d(-/-) mice. CD8(+) T lymphocytes were reduced in CD1d(-/-) mice of all strains, as shown by cell surface staining and major histocompatibility complex class I tetramer analysis, and resulted in strain-specific alterations in illness, viral clearance, and gamma interferon (IFN-gamma) production. Transient activation of NK T cells in CD1d(+/+) mice by alpha-GalCer resulted in reduced illness and delayed viral clearance. These data suggest that early IFN-gamma production and efficient induction of CD8(+)-T-cell responses during primary RSV infection require CD1d-dependent events. We also tested the ability of alpha-GalCer as an adjuvant to modulate the type 2 immune responses induced by RSV glycoprotein G or formalin-inactivated RSV immunization. However, immunized CD1-deficient or alpha-GalCer-treated wild-type mice did not exhibit diminished disease following RSV challenge. Rather, some disease parameters, including cytokine production, eosinophilia, and viral clearance, were increased. These findings indicate that CD1d-dependent NK T cells play a role in expansion of CD8(+) T cells and amplification of antiviral responses to RSV.

Regulatory natural killer T cells protect against spontaneous and recurrent type 1 diabetes

Autoimmune diseases, especially type 1 diabetes (T1D), may be caused by dysregulation of the immune system, which leads to hyporesponsiveness of regulatory T helper 2 (Th2) cells and promotion of autoimmune Th1 cells. Natural killer T (NKT) cells, which comprise a minor subpopulation of T cells, play a critical role in immunoregulation as a result of a rapid burst of IL-4 and IFN-gamma secretion. These cells are functionally and numerically deficient in individuals at risk of T1D, as well as in nonobese diabetic (NOD) mice. It is conceivable that protection from T1D may be achieved by correction of this deficiency. Alpha-galactosylceramide (alpha-GalCer) specifically binds to NKT cells in a CD1-dependent manner and stimulates these cells to proliferate and to produce various cytokines, including IFN-gamma, IL-4, and IL-10. In this review, we present evidence that a multiple-dose alpha-GalCer treatment regimen, which is known to promote a dominant Th2 environment, can prevent the onset of spontaneous and cyclophosphamide (CY)-accelerated T1D. This protection is associated with elevated IL-4 and IL-10 in the spleen and pancreas of protected female NOD mice. Concomitantly, IFN-gamma levels are reduced in both tissues. More importantly, the protective effect of gamma-GalCer in CY-accelerated T1D is abrogated by the in vivo blockade of IL-10 activity. We also show that alpha-GalCer treatment significantly prolongs syngeneic islet graft survival in recipient diabetic NOD mice. These findings raise the possibility that alpha-GalCer treatment may be used therapeutically to prevent the onset and recurrence of human T1D.

NKT cells - conductors of tumor immunity?

NKT cells are key players in the regulation of antitumor immunity, particularly in experimental models of tumor immunotherapy, such as IL-12 or alpha-galactosylceramide administration. They may also operate in natural antitumor immunity. NKT cells are best known for their immunosuppressive functions; however, NKT cells interact with a range of other cell types (particularly dendritic cells and NK cells) and the outcome of NKT-cell stimulation depends on these and on the cytokine/co-stimulatory milieu.

Cutting edge: analysis of human V alpha 24+CD8+ NK T cells activated by alpha-galactosylceramide-pulsed monocyte-derived dendritic cells

Human Valpha24(+) NKT cells constitute a counterpart of mouse Valpha14(+) NKT cells, both of which use an invariant TCR-alpha chain. The human Valpha24(+) NKT cells as well as mouse Valpha14(+) NKT cells are activated by glycolipids in a CD1d-restricted manner and produce many immunomodulatory cytokines, possibly affecting the immune balance. In mice, it has been considered from extensive investigations that Valpha14(+)CD8(+) NKT cells that express invariant TCR do not exist. Here we introduce human Valpha24(+)CD8(+) NKT cells. These cells share important features of Valpha24(+) NKT cells in common, but in contrast to CD4(-)CD8(-) (double-negative) or CD4(+) Valpha24(+) NKT cells, they do not produce IL-4. Our discovery may extend and deepen the research field of Valpha24(+) NKT cells as well as help to understand the mechanism of the immune balance-related diseases.

CD1d-restricted human natural killer T cells are highly susceptible to human immunodeficiency virus 1 infection

Human natural killer (NK) T cells are unique T lymphocytes that express an invariant T cell receptor (TCR) Valpha24-Vbeta11 and have been implicated to play a role in various diseases. A subset of NKT cells express CD4 and hence are potential targets for human immunodeficiency virus (HIV)-1 infection. We demonstrate that both resting and activated human Valpha24(+) T cells express high levels of the HIV-1 coreceptors CCR5 and Bonzo (CXCR6), but low levels of CCR7, as compared with conventional T cells. Remarkably NKT cells activated with alpha-galactosylceramide (alpha-GalCer)-pulsed dendritic cells were profoundly more susceptible to infection with R5-tropic, but not X4-tropic, strains of HIV-1, compared with conventional CD4(+) T cells. Furthermore, resting CD4(+) NKT cells were also more susceptible to infection. After initial infection, HIV-1 rapidly replicated and depleted the CD4(+) subset of NKT cells. In addition, peripheral blood NKT cells were markedly and selectively depleted in HIV-1 infected individuals. Although the mechanisms of this decline are not clear, low numbers or absence of NKT cells may affect the course of HIV-1 infection. Taken together, our findings indicate that CD4(+) NKT cells are directly targeted by HIV-1 and may have a potential role during viral transmission and spread in vivo.

Phenotypic and functional differences between NKT cells colonizing splanchnic and peripheral lymph nodes

NKT cells are considered unconventional T cells. First, they are restricted by a nonclassical MHC class I molecule, CD1d, which presents glycolipids; second, their TCR repertoire is very limited. After stimulation by their TCR, NKT cells rapidly release large amounts of cytokines, such as IL-4 and IFN-gamma. Little is known about NKT cells present in lymph nodes. In the present report we show that NKT cells are differently distributed in various lymph nodes and are, for instance, abundant in pancreatic and mesenteric lymph nodes of C57BL/6 mice and nonobese diabetic mice. The high frequency of NKT cells in splanchnic lymph nodes is not simply a consequence of inflammatory signals, as draining lymph nodes still contain low frequencies of NKT cells after IFA or CFA injections. NKT cells from splanchnic lymph nodes harbor a Vbeta repertoire similar to that of splenic and liver NKT cells, in contrast to peripheral NKT cells that are not biased toward Vbeta8 segments. Analysis of cytokine production by NKT cells from splanchnic lymph nodes reveals that they produce at least as much IL-4 as IFN-gamma, in contrast to NKT cells from other organs (spleen, liver, and peripheral lymph nodes), which produce much more IFN-gamma than IL-4. These specific features of NKT cells from splanchnic lymph nodes might explain their protective action against the development of pathogenic Th1 cells in type 1 diabetes.

Expansion of lung V alpha 14 NKT cells by administration of alpha-galactosylceramide-pulsed dendritic cells

NKT cells, a novel murine lymphoid lineage bearing an invariant T cell receptor encoded by V alpha 14 and J alpha 281 gene segments, recognize a specific ligand glycolipid, alpha-galactosylceramide (alpha-GalCer) in a CD1d-dependent manner. Recent research has revealed that activated V alpha 14 NKT cells have dramatic antitumor effects against a wide variety of tumor cell lines in vivo and in vitro. Here, we demonstrate strong in vivo antitumor effects brought about by treatment with alpha-GalCer-pulsed dendritic cells in comparison with in vitro-activated V alpha 14 NKT cells. Furthermore, we show a significant expansion of endogenous V alpha 14 NKT cells in the lung following the administration of alpha-GalCer-pulsed dendritic cells. The feasibility of immunotherapy with alpha-GalCer-pulsed dendritic cells is discussed.

Multiple immuno-regulatory defects in type-1 diabetes

Susceptibility to immune-mediated diabetes (IMD) in humans and NOD mice involves their inherently defective T cell immunoregulatory abilities. We have followed natural killer (NK) T cell numbers in patients with IMD, both by flow cytometry using mAbs to the characteristic junctions found in the T cell receptors of this cell subtype, and by semiquantitative RT-PCR for the corresponding transcripts. Both before and after clinical onset, the representation of these cells in patients' PBMCs is reduced. We also report low numbers of resting CD4(+) CD25(+) T cells in IMD patients, a subset of T cells shown to have important immunoregulatory functions in abrogating autoimmunities in 3-day thymectomized experimental mice. Whereas a biased Th1 to Th2 cytokine profile has been suggested to underlie the pathogenesis of IMD in both species, we found defective production of IFN-gamma in our patients after in vitro stimulation of their PBMCs by phorbol-myristate acetate and ionomycin and both IFN-gamma and IL-4 deficiencies in V(alpha)24(+) NK T-enriched cells. These data suggest that multiple immunoregulatory T (Treg) cell defects underlie islet cell autoimmunity leading to IMD in humans and that these lesions may be part of a broad T cell defect.

Understanding autoimmune diabetes: insights from mouse models

Type 1 or insulin-dependent diabetes is an autoimmune disease that causes the selective destruction of insulin-secreting beta cells in the pancreatic islets. Although this is a polygenic disease, with at least 20 genes implicated, the dominant susceptibility locus maps to the major histocompatibility complex (MHC), both in humans and in rodent models. However, in spite of progress on several fronts, the molecular pathology of autoimmune diabetes remains incompletely defined. Major areas of research include environmental trigger factors, the identification and role of beta-cell antigens in inducing and maintaining the autoimmune response, and the nature of the pathogenic and protective lymphocytes involved. In this review, we will focus on these areas to highlight recent advances in understanding the pathogenesis of autoimmune diabetes, drawing extensively on insights gained by studying the non-obese diabetic (NOD) mouse.

Immunotherapy of type 1 diabetes: lessons for other autoimmune diseases

The nonobese diabetic (NOD) mouse is a well-recognised animal model of spontaneous autoimmune insulin-dependent diabetes mellitus. The disease is T-cell mediated, involving both CD4 and CD8 cells. Its progress is controlled by a variety of regulatory T cells. An unprecedented number of immunological treatments have been assessed in this mouse strain. This chapter systematically reviews most of these therapeutic manoeuvres, discussing them in the context of their significance with regard to the underlying mechanisms and the potential clinical applications. The contrast between the surprisingly high rate of success found for a multitude of treatments (more than 160) administered early in the natural history of the disease and the few treatments active at a late stage is discussed in depth. Most of the concepts and strategies derived from this model apply to other autoimmune diseases, for which no such diversified data are available.

NKT cells and type-1 diabetes and the "hygiene hypothesis" to explain the rising incidence rates

Immune-mediated (type-1) diabetes (IMD) is a multigenetic disease that is strongly influenced by the environment. Whereas the incidence rates are steadily rising worldwide, less than half of affected identical twins ever become concordant for IMD or even beta-cell autoimmunity. Worldwide, it is the tropical regions of the world that are replete in infectious and parasitic diseases that are the least affected. Repeated efforts to identify the putative inductive agents for beta-cell autoimmunity have proved unrewarding. Rather, we suggest that some environments are less protective than others and argue that it is the fall in incidences of infectious diseases and intestinal parasites that are likely responsible for the rise in autoimmune diseases like IMD in the West. Nonobese diabetic (NOD) mice reared in gnotobiotic environments have only worsened diabetes, while recent studies suggest that multiple defects in immune tolerance to self must be present before IMD can develop in the human or mouse. We speculate herein that the deficiency in natural killer T (NKT) cells in IMD in both species may be both genetic and environmentally influenced, predisposing to pancreatic beta-cell autoimmunity through a dysfunction of immunoregulatory T cells, with defective peripheral control of islet cell protein autoreactive cytotoxic CD8+ T cells. The encouraging results in NOD mice using alpha-galactosylceramide to stimulate NKT cells now warrant trials with this and other glycolipid NKT cell-stimulating agents in humans. Since it has become apparent that autoimmune diseases such as IMD are the result of an underlying immunodeficiency state, we strongly argue that its effective prevention will likely come through the use of immunostimulation and not through side effect-prone immunosuppression.

Multiple immuno-regulatory defects in type-1 diabetes

Susceptibility to immune-mediated diabetes (IMD) in humans and NOD mice involves their inherently defective T cell immunoregulatory abilities. We have followed natural killer (NK) T cell numbers in patients with IMD, both by flow cytometry using mAbs to the characteristic junctions found in the T cell receptors of this cell subtype, and by semiquantitative RT-PCR for the corresponding transcripts. Both before and after clinical onset, the representation of these cells in patients' PBMCs is reduced. We also report low numbers of resting CD4(+) CD25(+) T cells in IMD patients, a subset of T cells shown to have important immunoregulatory functions in abrogating autoimmunities in 3-day thymectomized experimental mice. Whereas a biased Th1 to Th2 cytokine profile has been suggested to underlie the pathogenesis of IMD in both species, we found defective production of IFN-gamma in our patients after in vitro stimulation of their PBMCs by phorbol-myristate acetate and ionomycin and both IFN-gamma and IL-4 deficiencies in V(alpha)24(+) NK T-enriched cells. These data suggest that multiple immunoregulatory T (Treg) cell defects underlie islet cell autoimmunity leading to IMD in humans and that these lesions may be part of a broad T cell defect.

Natural killer T cell activation protects mice against experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) serves as a prototypic model for T cell-mediated autoimmunity. V(alpha)14 natural killer T (NKT) cells are a subset of T lymphocytes that recognize glycolipid antigens presented by the nonpolymorphic major histocompatibility complex (MHC) class I-like protein CD1d. Here, we show that activation of V(alpha)14 NKT cells by the glycosphingolipid alpha-galactosylceramide (alpha-GalCer) protects susceptible mice against EAE. beta-GalCer, which binds CD1d but is not recognized by NKT cells, failed to protect mice against EAE. Furthermore, alpha-GalCer was unable to protect CD1d knockout (KO) mice against EAE, indicating the requirement for an intact CD1d antigen presentation pathway. Protection of disease conferred by alpha-GalCer correlated with its ability to suppress myelin antigen-specific Th1 responses and/or to promote myelin antigen-specific Th2 cell responses. alpha-GalCer was unable to protect IL-4 KO and IL-10 KO mice against EAE, indicating a critical role for both of these cytokines. Because recognition of alpha-GalCer by NKT cells is phylogenetically conserved, our findings have identified NKT cells as novel target cells for treatment of inflammatory diseases of the central nervous system.

Activation of natural killer T cells potentiates or prevents experimental autoimmune encephalomyelitis

Natural killer (NK) T cells recognize lipid antigens in the context of the major histocompatibility complex (MHC) class 1-like molecule CD1 and rapidly secrete large amounts of the cytokines interferon (IFN)-gamma and interleukin (IL)-4 upon T cell receptor (TCR) engagement. We have asked whether NK T cell activation influences adaptive T cell responses to myelin antigens and their ability to cause experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. While simultaneous activation of NK T cells with the glycolipid alpha-galactosylceramide (alpha-GalCer) and myelin-reactive T cells potentiates EAE in B10.PL mice, prior activation of NK T cells protects against disease. Exacerbation of EAE is mediated by an enhanced T helper type 1 (Th1) response to myelin basic protein and is lost in mice deficient in IFN-gamma. Protection is mediated by immune deviation of the anti-myelin basic protein (MBP) response and is dependent upon the secretion of IL-4. The modulatory effect of alpha-GalCer requires the CD1d antigen presentation pathway and is dependent upon the nature of the NK T cell response in B10.PL or C57BL/6 mice. Because CD1 molecules are nonpolymorphic and remarkably conserved among different species, modulation of NK T cell activation represents a target for intervention in T cell-mediated autoimmune diseases.

CD4(+) regulatory T cells

There is now compelling evidence that CD4(+) T cells that specialize in the suppression of immune responses play a key role in the control of immune pathology. Recently, there have been a number of reports that have provided information on the generation of CD4(+) regulatory T cells in the thymus and in the periphery. These cells have also been identified in humans, paving the way for analysis of the function of CD4(+) regulatory T cells in immune-mediated disease.

Autoreactivity by design: innate B and T lymphocytes

Innate B and T lymphocytes are a subset of lymphocytes that express a restricted set of semi-invariant, germ-line-encoded, autoreactive antigen receptors. Although they have long been set apart from mainstream immunological thought, they now seem to represent a distinct immune-recognition strategy that targets conserved stress-induced self-structures, rather than variable foreign antigens. Innate lymphocytes regulate a range of infectious, tumour and autoimmune conditions. New studies have shed light on the principles and mechanisms that drive their unique development and function, and show their resemblance to another subset of innate lymphocytes, the natural killer cells.

Activation of CD1d-restricted T cells protects NOD mice from developing diabetes by regulating dendritic cell subsets

CD1d-restricted invariant NKT (iNKT) cells are immunoregulatory cells whose loss exacerbates diabetes in nonobese diabetic (NOD) female mice. Here, we show that the relative numbers of iNKT cells from the pancreatic islets of NOD mice decrease at the time of conversion from peri-insulitis to invasive insulitis and diabetes. Conversely, NOD male mice who have a low incidence of diabetes showed an increased frequency of iNKT cells. Moreover, administration of alpha-galactosylceramide, a potent activating ligand presented by CD1d, ameliorated the development of diabetes in NOD female mice and resulted in the accumulation of iNKT cells and myeloid dendritic cells (DC) in pancreatic lymph nodes (PLN), but not in inguinal lymph nodes. Strikingly, injection of NOD female mice with myeloid DC isolated from the PLN, but not those from the inguinal lymph nodes, completely prevented diabetes. Thus, the immunoregulatory role of iNKT cells is manifested by the recruitment of tolerogenic myeloid DC to the PLN and the inhibition of ongoing autoimmune inflammation.

Activation of natural killer T cells by alpha-galactosylceramide treatment prevents the onset and recurrence of autoimmune Type 1 diabetes

Type 1 diabetes (T1D) in non-obese diabetic (NOD) mice may be favored by immune dysregulation leading to the hyporesponsiveness of regulatory T cells and activation of effector T-helper type 1 (Th1) cells. The immunoregulatory activity of natural killer T (NKT) cells is well documented, and both interleukin (IL)-4 and IL-10 secreted by NKT cells have important roles in mediating this activity. NKT cells are less frequent and display deficient IL-4 responses in both NOD mice and individuals at risk for T1D (ref. 8), and this deficiency may lead to T1D (refs. 1,6-9). Thus, given that NKT cells respond to the alpha-galactosylceramide (alpha-GalCer) glycolipid in a CD1d-restricted manner by secretion of Th2 cytokines, we reasoned that activation of NKT cells by alpha-GalCer might prevent the onset and/or recurrence of T1D. Here we show that alpha-GalCer treatment, even when initiated after the onset of insulitis, protects female NOD mice from T1D and prolongs the survival of pancreatic islets transplanted into newly diabetic NOD mice. In addition, when administered after the onset of insulitis, alpha-GalCer and IL-7 displayed synergistic effects, possibly via the ability of IL-7 to render NKT cells fully responsive to alpha-GalCer. Protection from T1D by alpha-GalCer was associated with the suppression of both T- and B-cell autoimmunity to islet beta cells and with a polarized Th2-like response in spleen and pancreas of these mice. These findings raise the possibility that alpha-GalCer treatment might be used therapeutically to prevent the onset and recurrence of human T1D.