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

Genetic control of murine invariant natural killer T-cell development dynamically differs dependent on the examined tissue type

Previous studies using gene-targeted mutant mice revealed several molecules important for the development or function of invariant natural killer T (iNKT) cells. However, these gene knockout mice represent cases that are rare in humans. Thus, it remains unclear how naturally occurring allelic variants of these genes or others regulate the numerical and functional diversity of iNKT cells in both mice and humans. Studies in humans are mostly limited to iNKT cells in peripheral blood (PB). It is not known if the relative distribution of iNKT cells between PB and other lymphoid organs is correlated or under common genetic control. To initially address these questions, we analyzed iNKT cells in the spleen, thymus and PB of 38 inbred mouse strains. Percentages of iNKT cells in these three anatomical sites varied significantly in a strain-dependent manner. The correlation between PB and spleen was moderate, and none was observed between PB and thymus. Similarly, proportions of the CD4-expressing subset of iNKT cells differed significantly among inbred strains. The percentages of CD4-positive iNKT cells displayed a strong correlation between PB and spleen, although it remained poor between PB and thymus. Genome-wide association studies across strains identified only partially overlapping loci associated with variability of iNKT cell frequencies within and between differing anatomical sites.

NKT cells are required for complete Freund's adjuvant-mediated protection from autoimmune diabetes

Autoimmune diabetes in NOD mice can be prevented by application of Ags derived from Mycobacterium tuberculosis in the form of bacillus Calmette-Guérin or CFA. Disease protection by CFA is associated with a reduction in the numbers of pathogenic β-cell specific, self-reactive CTLs, a phenomenon dependent on the presence and function of NK cells. However, the mechanisms by which NK cells are activated and recruited by heat-killed M. tuberculosis within CFA are unclear. In this study, we report that CFA-mediated NK cell activation and mobilization is dependent on CD1d expression. The administration of M. tuberculosis from CFA results in rapid NKT cell activation and IFN-γ secretion both in vitro and in vivo. CFA-induced NKT cell activation is intact in MyD88(-/-) mice suggesting that the mechanism is independent of TLR signaling. Furthermore, CD1d expression was found to be essential for both M. tuberculosis-triggered NKT cell activation and CFA-mediated protection of NOD mice from diabetes. Collectively, these findings reveal hitherto previously unidentified roles for NKT cells in the adjuvant-promoting effects of CFA on innate and adaptive immunity.

Cholesterol, Cytokines and Diseases

A high level of cholesterol is associated with obesity, cardiovascular diseases and atherosclerosis. Immune response in atherosclerosis is mediated by chemokines which attract monocytes, leading to the innate immune response characterised by the production of cytokines. The immunoregulatory cytokines are an important bridge between innate and adductive immunity. TH1 cytokines are involved as effector T cells in inflammatory response, while TH2 cytokines can be anti-inflammatory such as IL-10 and IL-4. It is well known that statins enhance the production of TH2 cytokines whereas the secretion of TH1 cytokines is suppressed. For this purpose, we studied the significance of anti-inflammatory effect and suppression of inflammation by statins. In this paper we revisited the role of cholesterol and cytokines IL-18, IL-10, IL-12, TNF-α, interferon-γ, and chemokines in inflammatory diseases.

Invariant NKT cell anergy is induced by a strong TCR-mediated signal plus co-stimulation

Vα14 TCR expressing invariant NK T (iNKT) cells recognize α-galactosylceramide (αGC)/CD1d complex and produce large amounts of various cytokines before the onset of the adaptive immunity. After stimulation with a high dose (2-5 μg) of αGC in vivo, iNKT cells in the spleen and liver become anergic in terms of the proliferation and cytokine production to subsequent stimulation. In this study, we monitor how iNKT anergy is induced. Anergized iNKT cells dramatically reduced the expression of IL-2Rα, and exogenous IL-2 restored the ability to proliferate and produce IL-4 but not to produce IFN-γ. Anergized iNKT cells expressed high levels of programmed death-1 (PD-1). However, iNKT cells in PD-1-deficient mice became anergic as a result of αGC injection, as do normal mice. Furthermore, anti-PD-1 blocking mAb was unable to restore their responsiveness. When iNKT cells were stimulated with immobilized anti-CD3 in the presence or absence of anti-CD28, they produced cytokines in a dose-dependent manner. Unlike in naive CD4 T cells, the strong TCR-mediated signaling with co-stimulation renders them anergic to any subsequent stimulation with αGC and spleen dendritic cells (DCs). Moreover, iNKT cells also became anergic after stimulation with phorbol-12-myristate-13-acetate + ionophore. Finally, the injection of αGC-pulsed DCs was more potent in inducing anergy than B cells. These results indicate that strong TCR-mediated activation with co-stimulation provides signals that induce the anergic state in iNKT cells.

Marine bioactives as functional food ingredients: potential to reduce the incidence of chronic diseases

The marine environment represents a relatively untapped source of functional ingredients that can be applied to various aspects of food processing, storage, and fortification. Moreover, numerous marine-based compounds have been identified as having diverse biological activities, with some reported to interfere with the pathogenesis of diseases. Bioactive peptides isolated from fish protein hydrolysates as well as algal fucans, galactans and alginates have been shown to possess anticoagulant, anticancer and hypocholesterolemic activities. Additionally, fish oils and marine bacteria are excellent sources of omega-3 fatty acids, while crustaceans and seaweeds contain powerful antioxidants such as carotenoids and phenolic compounds. On the basis of their bioactive properties, this review focuses on the potential use of marine-derived compounds as functional food ingredients for health maintenance and the prevention of chronic diseases.

Sulfatide-reactive natural killer T cells abrogate ischemia-reperfusion injury

There is a significant immune response to ischemia-reperfusion injury (IRI), but the role of immunomodulatory natural killer T (NKT) cell subtypes is not well understood. Here, we compared the severity of IRI in mice deficient in type I/II NKT cells (CD1d(-/-)) or type I NKT cells (Jα18(-/-)). The absence of NKT cells, especially type II NKT cells, accentuated the severity of renal injury, whereas repletion of NKT cells attenuated injury. Adoptively transferred NKT cells trafficked into the tubulointerstitium, which is the primary area of injury. Sulfatide-induced activation of type II NKT cells protected kidneys from IRI, but inhibition of NKT cell recruitment enhanced injury. In co-culture experiments, sulfatide-induced activation of NKT cells from either mice or humans attenuated apoptosis of renal tubular cells after transient hypoxia via hypoxia-inducible factor (HIF)-1α and IL-10 pathways. Renal tissue of patients with acute tubular necrosis (ATN) frequently contained NKT cells, and the number of these cells tended to negatively correlate with ATN severity. In summary, sulfatide-reactive type II NKT cells are renoprotective in IRI, suggesting that pharmacologic modulation of NKT cells may protect against ischemic injury.

Activation of human invariant natural killer T cells with a thioglycoside analogue of α-galactosylceramide

Activation of CD1d-restricted invariant NKT (iNKT) cells with the glycolipid α-galactosylceramide (α-GalCer) confers protection against disease in murine models, however, clinical trials in humans have had limited impact. We synthesized a novel thioglycoside analogue of α-GalCer, denoted α-S-GalCer, and tested its efficacy for stimulating human iNKT cells in vitro. α-S-GalCer stimulated cytokine release by iNKT cells in a CD1d-dependent manner and primed CD1d(+) target cells for lysis. α-S-GalCer-stimulated iNKT cells induced maturation of monocyte-derived dendritic cells into antigen-presenting cells that released IL-12 and small amounts of IL-10. The nature and potency of α-S-GalCer and α-GalCer in human iNKT cell activation were similar. However, in contrast to α-GalCer, α-S-GalCer did not activate murine iNKT cells in vivo. Because of its enhanced stability in biological systems, α-S-GalCer may be superior to α-GalCer as a parent compound for developing adjuvant therapies for humans.

Invariant NK T cells: potential for immunotherapeutic targeting with glycolipid antigens

Invariant NK T (iNKT) cells are a subset of T lymphocytes that recognize glycolipid antigens bound with the antigen-presenting molecule CD1d. iNKT cells have potent immunoregulatory activities that can promote or suppress immune responses during different pathological conditions. These immunoregulatory properties can be harnessed for therapeutic purposes with cognate glycolipid antigens, such as the marine sponge-derived glycosphingolipid α-galactosylceramide. Preclinical studies have shown substantial promise for iNKT cell-based treatments of infections, cancer and autoimmune and inflammatory diseases. Translation of these preclinical studies to the clinic, while faced with some obstacles, has already had some initial success. In this article, we review the immunodulatory activities of iNKT cells and the potential for developing iNKT cell-based prophylactic and curative therapies of human disease.

Alcohol facilitates CD1d loading, subsequent activation of NKT cells, and reduces the incidence of diabetes in NOD mice

Background

Ethanol (‘alcohol’) is a partly hydrophobic detergent that may affect the accessibility of glycolipids thereby influencing immunological effects of these molecules.

Methods

The study included cellular in vitro tests using α-galactosylceramide (αGalCer), and in vivo NOD mice experiments detecting diabetes incidence and performing behavioural and bacterial analyses.

Results

Alcohol in concentrations from 0.6% to 2.5% increased IL-2 production from NKT cells stimulated with αGalCer by 60% (p<0.05). CD1d expressed on HeLa cells contained significantly increasing amounts of αGalCer with increasing concentrations of alcohol, suggesting that alcohol facilitated the passive loading of αGalCer to CD1d. NOD mice were found to tolerate 5% ethanol in their drinking water without signs of impairment in liver function. Giving this treatment, the diabetes incidence declined significantly. Higher numbers of CD3+CD49b+ NKT cells were found in spleen and liver of the alcohol treated compared to the control mice (p<0.05), whereas the amount of CD4+Foxp3+ regulator T cells did not differ. Increased concentrations of IFN-γ were detected in 24-hour blood samples of alcohol treated mice. Behavioural studies showed no change in attitude of the ethanol-consuming mice, and bacterial composition of caecum samples was not affected by alcohol, disqualifying these as protective mechanisms.

Conclusion

Alcohol facilitates the uptake of glycolipids and the stimulation of NKT cells, which are known to counteract Type 1 diabetes development. We propose that this is the acting mechanism by which treatment with alcohol reduces the incidence of diabetes in NOD mice. This is corroborated by epidemiology showing beneficial effect of alcohol to reduce the severity of atherosclerosis and related diseases.

The requirement of natural killer T-cells in tolerogenic APCs-mediated suppression of collagen-induced arthritis

TGF-beta-induced tolerogenic-antigen presenting cells (Tol-APCs) could induce suppression of autoimmune diseases such as collagen-induced arthritis (CIA) and allergic asthma. In contrast, many studies have shown that NKT cells are involved in the pathogenesis of Th1-mediated autoimmune joint inflammation and Th2-mediated allergic pulmonary inflammation. In this study, we investigated the effect of CD1d-restricted NKT cells in the Tol-APCs-mediated suppression of autoimmune disease using a murine CIA model. When CIA-induced mice were treated with Tol-APCs obtained from CD1d+/- or CD1d-/- mice, unlike CD1d+/- APCs, CD1d-/- Tol-APCs failed to suppress CIA. More specifically, CD1d-/- Tol-APCs failed to suppress the production of inflammatory cytokines and the induction of Th2 responses by antigen-specific CD4 T cells both in vitro and in vivo. Our results demonstrate that the presence of CD1d-restricted NKT cells is critical for the induction of Tol-APCs-mediated suppression of CIA.

α-Galactosylceramide ameliorates autoimmune diabetes in non-obese diabetic mice through a suppressive effect mediated by CD8+ T cells

Type 1 diabetes is an autoimmune disorder resulting from lymphocyte-mediated destruction of insulin-producing β cells in pancreas. Natural killer T cells are regulatory immune components controlling autoreactivity and immune homeostasis. Although early studies supported that amelioration of autoimmune diabetes by natural killer T cells was associated with Th1/2 shift, other Th2-independent regulatory mechanisms were also suggested. Since natural killer T cells are critical for the generation of CD8(+) regulatory T cells controlling anterior chamber-associated immune deviation and CD8(+) regulatory T cells also participate in suppression of immune responses like experimental autoimmune encephalomyelitis, we investigate whether the similar suppressive effects are involved in α-galactosylceramide-induced immune tolerance in non-obese diabetic mice. We demonstrate that repeated exposure of α-galactosylceramide reveals a hyporesponsiveness of total or antigen-presenting cells-depleted splenocytes upon anti-CD3/28 antibodies stimulation. The dispensability of dendritic cells in the hyporesponsiveness is consistent with the comparable expression of costimulatory molecules on CD11c(+) subsets between α-galactosylceramide- and vehicle-treated mice. α-Galactosylceramide treatment not only affects the effector T cell subsets and their cytokine production but also increases the secretion of transforming growth factor-β by splenocytes, implying the suppressive regulation. The adoptive transfer experiments demonstrate the suppressive effect of T cells from α-galactosylceramide-treated non-obese diabetic mice when co-transferred with vehicle-treated littermates. Finally, it reveals that CD8(+) subset among antigen-presenting cells-depleted splenocytes tends to confer the suppression since the protective ability vanishes upon withdrawal of CD8(+) subset. These results suggest that repeated exposure of α-galactosylceramide ameliorates autoimmune diabetes in non-obese diabetic mice mediated by CD8(+) T cell-associated suppression.

Activation of natural killer T cells by α-carba-GalCer (RCAI-56), a novel synthetic glycolipid ligand, suppresses murine collagen-induced arthritis

Alpha-carba-GalCer (RCAI-56), a novel synthetic analogue of α-galactosylceramide (α-GalCer), stimulates invariant natural killer T (NK T) cells to produce interferon (IFN)-γ. IFN-γ exhibits immunoregulatory properties in autoimmune diseases by suppressing T helper (Th)-17 cell differentiation and inducing regulatory T cells and apoptosis of autoreactive T cells. Here, we investigated the protective effects of α-carba-GalCer on collagen-induced arthritis (CIA) in mice. First, we confirmed that α-carba-GalCer selectively induced IFN-γ in CIA-susceptible DBA/1 mice in vivo. Then, DBA/1 mice were immunized with bovine type II collagen (CII) and α-carba-GalCer. The incidence and clinical score of CIA were significantly lower in α-carba-GalCer-treated mice. Anti-IFN-γ antibodies abolished the beneficial effects of α-carba-GalCer, suggesting that α-carba-GalCer ameliorated CIA in an IFN-γ-dependent manner. Treatment with α-carba-GalCer reduced anti-CII antibody production [immunoglobulin (Ig)G and IgG2a] and CII-reactive interleukin (IL)-17 production by draining lymph node (DLN) cells, did not induce apoptosis or regulatory T cells, and significantly increased the ratio of the percentage of IFN-γ-producing T cells to IL-17-producing T cells (Th1/Th17 ratio). Moreover, the gene expression levels of IL-6 and IL-23p19, Th17-related cytokines, were reduced significantly in mice treated with α-carba-GalCer. In addition, we observed higher IFN-γ production by NK T cells in α-carba-GalCer-treated mice in the initial phase of CIA. These findings indicate that α-carba-GalCer polarizes the T cell response toward Th1 and suppresses Th17 differentiation or activation, suggesting that α-carba-GalCer, a novel NK T cell ligand, can potentially provide protection against Th17-mediated autoimmune arthritis by enhancing the Th1 response.

Stimulation of a shorter duration in the state of anergy by an invariant natural killer T cell agonist enhances its efficiency of protection from type 1 diabetes

We have reported previously that treatment of non-obese diabetic (NOD) mice with the invariant natural killer T (iNK T) cell agonist α-galactosylceramide C26:0 (α-GalCer) or its T helper type 2 (Th2)-biasing derivative α-GalCer C20:2 (C20:2) protects against type 1 diabetes (T1D), with C20:2 yielding greater protection. After an initial response to α-GalCer, iNK T cells become anergic upon restimulation. While such anergic iNK T cells can induce tolerogenic dendritic cells (DCs) that mediate protection from T1D, chronic administration of α-GalCer also results in long-lasting anergy accompanied by significantly reduced iNK T cell frequencies, which raises concerns about its long-term therapeutic use. In this study, our objective was to understand more clearly the roles of anergy and induction of tolerogenic DCs in iNK T cell-mediated protection from T1D and to circumvent potential complications associated with α-GalCer. We demonstrate that NOD iNK T cells activated during multi-dose (MD) treatment in vivo with C20:2 enter into and exit from anergy more rapidly than after activation by α-GalCer. Importantly, this shorter duration of iNK T cells in the anergic state promotes the more rapid induction of tolerogenic DCs and reduced iNK T cell death, and enables C20:2 stimulated iNK T cells to elicit enhanced protection from T1D. Our findings further that suggest C20:2 is a more effective therapeutic drug than α-GalCer for protection from T1D. Moreover, the characteristics of C20:2 provide a basis of selection of next-generation iNK T cell agonists for the prevention of T1D.

Role of SLAM in NKT cell development revealed by transgenic complementation in NOD mice

Allelic variation of SLAM expression on CD4(+)CD8(+) thymocytes has been proposed to play a major role in NKT cell development. In this article, this hypothesis is tested by the production of subcongenic mouse strains and Slamf1 transgenic lines. The long isoform of the C57BL/6 allele of Slamf1 was transgenically expressed on CD4(+)CD8(+) thymocytes under control of an hCD2 minigene. NOD.Nkrp1b.Tg(Slamf1)1 mice, which had a 2-fold increase in SLAM protein expression on CD4(+)CD8(+) thymocytes, had a 2-fold increase in numbers of thymic NKT cells. The additional thymic NKT cells in NOD.Nkrp1b.Tg(Slamf1)1 mice were relatively immature, with a similar subset distribution to those of congenic NOD.Nkrp1b.Nkt1 and NOD.Nkrp1b.Slamf1 mice, which also express increased levels of SLAM on CD4(+)CD8(+) thymocytes and produce larger numbers of NKT cells. Transgenic enhancement of SLAM expression also increased IL-4 and IL-17 production in response to TCR-mediated stimulation. Paradoxically, NOD.Nkrp1b.Tg(Slamf1)2 mice, which had a 7-fold increase in SLAM expression, showed no significant increase in NKT cells numbers; on the contrary, at high transgene copy number, SLAM expression levels correlated inversely with NKT cell numbers, consistent with a contribution to negative selection. These data confirm a role for SLAM in controlling NKT cell development and are consistent with a role in both positive and negative thymic selection of NKT cells.

Genetic control of hepatitis A severity and susceptibility to allergy

Hepatitis A virus (HAV) usually results in asymptomatic infection or mild disease, but in a small subset of patients it can lead to severe disease and even liver failure. In this issue of the JCI, Kim et al. identify a polymorphism associated with this increased disease risk in the gene that encodes the HAV receptor--TIM1. Importantly, this TIM1 gene polymorphism protects from the development of atopic diseases in HAV-seropositive individuals.

Cross-talk between cd1d-restricted nkt cells and γδ cells in t regulatory cell response

CD1d is a non-classical major histocompatibility class 1-like molecule which primarily presents either microbial or endogenous glycolipid antigens to T cells involved in innate immunity. Natural killer T (NKT) cells and a subpopulation of γδ T cells expressing the Vγ4 T cell receptor (TCR) recognize CD1d. NKT and Vγ4 T cells function in the innate immune response via rapid activation subsequent to infection and secrete large quantities of cytokines that both help control infection and modulate the developing adaptive immune response. T regulatory cells represent one cell population impacted by both NKT and Vγ4 T cells. This review discusses the evidence that NKT cells promote T regulatory cell activation both through direct interaction of NKT cell and dendritic cells and through NKT cell secretion of large amounts of TGFβ, IL-10 and IL-2. Recent studies have shown that CD1d-restricted Vγ4 T cells, in contrast to NKT cells, selectively kill T regulatory cells through a caspase-dependent mechanism. Vγ4 T cell elimination of the T regulatory cell population allows activation of autoimmune CD8+ effector cells leading to severe cardiac injury in a coxsackievirus B3 (CVB3) myocarditis model in mice. CD1d-restricted immunity can therefore lead to either immunosuppression or autoimmunity depending upon the type of innate effector dominating during the infection.

Natural killer T cells in health and disease

Natural killer T (NKT) cells are a subset of T lymphocytes that share surface markers and functional characteristics with both conventional T lymphocytes and natural killer cells. Most NKT cells express a semi-invariant T cell receptor that reacts with glycolipid antigens presented by the major histocompatibility complex class I-related protein CD1d on the surface of antigen-presenting cells. NKT cells become activated during a variety of infections and inflammatory conditions, rapidly producing large amounts of immunomodulatory cytokines. NKT cells can influence the activation state and functional properties of multiple other cell types in the immune system and, thus, modulate immune responses against infectious agents, autoantigens, tumors, tissue grafts and allergens. One attractive aspect of NKT cells is that their immunomodulatory activities can be readily harnessed with cognate glycolipid antigens, such as the marine sponge-derived glycosphingolipid alpha-galactosylceramide. These properties of NKT cells are being exploited for therapeutic intervention to prevent or treat cancer, infections, and autoimmune and inflammatory diseases.

Invariant NKT cells regulate experimental autoimmune uveitis through inhibition of Th17 differentiation

Although NKT cells have been implicated in diverse immunomodulatory responses, the effector mechanisms underlying the NKT cell-mediated regulation of pathogenic T helper cells are not well understood. Here, we show that invariant NKT cells inhibited the differentiation of CD4(+) T cells into Th17 cells both in vitro and in vivo. The number of IL-17-producing CD4(+) T cells was reduced following co-culture with purified NK1.1(+) TCR(+) cells from WT, but not from CD1d(-/-) or Jα18(-/-) , mice. Co-cultured NKT cells from either cytokine-deficient (IL-4(-/-) , IL-10(-/-) , or IFN-γ(-/-) ) or WT mice efficiently inhibited Th17 differentiation. The contact-dependent mechanisms of NKT cell-mediated regulation of Th17 differentiation were confirmed using transwell co-culture experiments. On the contrary, the suppression of Th1 differentiation was dependent on IL-4 derived from the NKT cells. The in vivo regulatory capacity of NKT cells on Th17 cells was confirmed using an experimental autoimmune uveitis model induced with human IRBP(1-20) (IRBP, interphotoreceptor retinoid-binding protein) peptide. NKT cell-deficient mice (CD1d(-/-) or Jα18(-/-) ) demonstrated an increased disease severity, which was reversed by the transfer of WT or cytokine-deficient (IL-4(-/-) , IL-10(-/-) , or IFN-γ(-/-) ) NKT cells. Our results indicate that invariant NKT cells inhibited autoimmune uveitis predominantly through the cytokine-independent inhibition of Th17 differentiation.

Clinical development of a novel CD1d-binding NKT cell ligand as a vaccine adjuvant

Natural killer T (NKT) cells are known to play a role against certain microbial infections, including malaria and HIV, two major global infectious diseases. Strategies that can harness and amplify the immunotherapeutic potential of NKT cells can serve as powerful tools in the fight against such diseases. 7DW8-5, a novel glycolipid, may be one such tool. The interaction of 7DW8-5 with CD1d molecules induces activation of NKT cells, thereby activating various immune-competent cells including dendritic cells (DCs) to provide a significant adjuvant effect for several vaccines. This review discusses the discovery and characterization of 7DW8-5 and the practical considerations of its preclinical and clinical development as a potential glycolipid adjuvant for candidate malaria and HIV vaccines.

Mechanism of regulation of autoimmunity by iNKT cells

iNKT cells, CD1d dependent natural killer T cells are a unique population of T cells. The capacity of iNKT cells to produce regulatory cytokines first provided an indication of their regulatory potential. Later on, in experimental models as well as in patients afflicted with an auto-immune disease, such as Type 1 diabetes mellitus, multiple sclerosis, and systemic lupus erythematosus along with others, a deficit in iNKT cell number was observed, suggesting the role these cells may possibly have in the prevention of auto-immune diseases. More importantly, experimental strategies which focused on increasing the volume or stimulation of iNKT cells in laboratory animals, demonstrated an improved level of protection against the development of auto-immune diseases. This article reviews the mechanism of protection against autoimmunity by iNKT cells, discusses the obstacles against and indications for the potential use of iNKT cell manipulation in the treatment of human auto-immune diseases.

On/off TLR signaling decides proinflammatory or tolerogenic dendritic cell maturation upon CD1d-mediated interaction with invariant NKT cells

Invariant NKT (iNKT) cells play an effector/adjuvant function during antimicrobial and antitumoral immunity and a regulatory role to induce immune tolerance and prevent autoimmunity. iNKT cells that differentially modulate adaptive immunity do not bear a unique phenotype and/or specific cytokine secretion profile, thus opening questions on how a single T cell subset can exert opposite immunological tasks. In this study, we show that iNKT cells perform their dual roles through a single mechanism of action relying on the cognate interaction with myeloid dendritic cells (DCs) and leading to opposite effects depending on the presence of other maturation stimuli simultaneously acting on DCs. The contact of murine purified iNKT cells with immature autologous DCs directly triggers the tolerogenic maturation of DCs, rendering them able to induce regulatory T cell differentiation and prevent autoimmune diabetes in vivo. Conversely, the interaction of the same purified iNKT cells with DCs, in the presence of simultaneous TLR4 stimulation, significantly enhances proinflammatory DC maturation and IL-12 secretion. The different iNKT cell effects are mediated through distinct mechanisms and activation of different molecular pathways within the DC: CD1d signaling and activation of the ERK1/2 pathway for the tolerogenic action, and CD40-CD40L interaction and NF-κB activation for the adjuvant effect. Our data suggest that the DC decision to undergo proinflammatory or tolerogenic maturation results from the integration of different signals received at the time of iNKT cell contact and could have important therapeutic implications for exploiting iNKT cell adjuvant/regulatory properties in autoimmune diseases, infections, and cancer.

Introduction of aromatic group on 4'-OH of α-GalCer manipulated NKT cell cytokine production

The glycosphingolipid α-GalCer has been found to influence mammalian immune system significantly through the natural killer T cells. Unfortunately, the pre-clinical and clinical studies revealed several critical disadvantages that prevented the therapeutic application of α-GalCer in treating cancer and other diseases. Recently, the detailed illustration of the CD1d/α-GalCer/NKT TCR complex crystal structural, together with other latest structural and biological understanding on glycolipid ligands and NKT cells, provided a new platform for developing novel glycolipid ligands with optimized therapeutic effects. Here, we designed a series of novel aromatic group substituted α-GalCer analogues. The biological activity of these analogues was characterized and the results showed the unique substitution group manipulated the immune responses of NKT cells. Computer modeling and simulation study indicated the analogues had unique binding mode when forming CD1d/glycolipid/NKT TCR complex, comparing to original α-GalCer.

Type-specific human papillomavirus detection in cervical smears in Romania

To study type 1 diabetes (T1D), excellent animal models exist, both spontaneously diabetic and virus-induced. Based on knowledge from these, this review focuses on the environmental factors leading to T1D, concentrated into four areas which are: (1) The thymus-dependent immune system: T1D is a T cell driven disease and the beta cells are destroyed in an inflammatory insulitis process. Autoimmunity is breakdown of self-tolerance and the balance between regulator T cells and aggressive effector T cells is disturbed. Inhibition of the T cells (by e.g. anti-CD3 antibody or cyclosporine) will stop the T1D process, even if initiated by virus. Theoretically, the risk from immunotherapy elicits a higher frequency of malignancy. (2) The activity of the beta cells: Resting beta cells display less antigenicity and are less sensitive to immune destruction. Beta-cell rest can be induced by giving insulin externally in metabolic doses or by administering potassium-channel openers. Both procedures prevent T1D in animal models, whereas no good human data exist due to the risk of hypoglycemia. (3) NKT cells: According to the hygiene hypothesis, stimulation of NKT cells by non-pathogen microbes gives rise to less T cell reaction and less autoimmunity. Glycolipids presented by CD1 molecules are central in this stimulation. (4) Importance of the intestine and gliadin intake: Gluten-free diet dramatically inhibits T1D in animal models, and epidemiological data are supportive of such an effect in humans. The mechanisms include less subclinical intestinal inflammation and permeability, and changed composition of bacterial flora, which can also be obtained by intake of probiotics. Gluten-free diet is difficult to implement, and short-term intake has no effect. Regarding the onset of the T1D disease process, slow-acting enterovirus and gliadin deposits are speculated to be etiological in genetically susceptible individuals, followed by the mentioned four pathogenetic factors acting in concert. Neutralization of any one of these factors is capable of stopping T1D development, as lessons are learned from the animal models.

Lysosomal alpha-galactosidase controls the generation of self lipid antigens for natural killer T cells

Natural Killer T (NKT) cells are lipid-reactive, CD1d-restricted T lymphocytes important in infection, cancer, and autoimmunity. In addition to foreign antigens, NKT cells react with endogenous self lipids. However, in the face of stimulating self antigen, it remains unclear how overstimulation of NKT cells is avoided. We hypothesized that constantly degraded endogenous antigen only accumulates upon inhibition of alpha-galactosidase A (alpha-Gal-A) in lysosomes. Here, we show that alpha-Gal-A deficiency caused vigorous activation of NKT cells. Moreover, microbes induced inhibition of alpha-Gal-A activity in antigen-presenting cells. This temporary enzyme block depended on Toll-like receptor (TLR) signaling and ultimately triggered lysosomal lipid accumulation. Thus, we present TLR-dependent negative regulation of alpha-Gal-A as a mechanistic link between pathogen recognition and self lipid antigen induction for NKT cells.

The dangerous liaison between iNKT cells and dendritic cells: does it prevent or promote autoimmune diseases?

Invariant natural killer T (iNKT) cells represent an important regulatory T-cell subset that perceives signals of danger and/or cellular distress and modulate the adaptive immune response accordingly. In the presence of pathogens, iNKT cells acquire an adjuvant function that is fundamental to boost anti-microbial and anti-tumor immunity. At the same time, iNKT cells can play a negative regulatory function to maintain peripheral T-cell tolerance toward self-antigens and to prevent autoimmune disease. Both these effects of iNKT cells involve the modulation of the activity of dendritic cells (DCs) through cell-cell interaction. Indeed, iNKT cells can either boost Th1 immunity by enhancing maturation of pro-inflammatory DCs or promote immune tolerance through the maturation of tolerogenic DCs. This dual action of iNKT cells opens questions on the modalities by which a single-cell subset can exert opposite effects on DCs and may even put in question the overall immunosuppressive properties of iNKT cells. This review presents the large body of evidence that shows the ability of iNKT cells to negatively regulate autoimmunity and to prevent autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus. In addition, an update is provided on the mechanisms of iNKT-DCs interactions and how this can result in inflammatory or tolerogenic responses.

Identification of regulatory Foxp3+ invariant NKT cells induced by TGF-beta

Invariant NKT (iNKT) cells were shown to prevent the onset of experimental autoimmune encephalomyelitis in mice following administration of their specific TCR agonist alpha-galactosylceramide. We found that this protection was associated with the emergence of a Foxp3(+) iNKT cell population in cervical lymph nodes. We demonstrate that the differentiation of these cells is critically dependent on TGF-beta in both mice and humans. Moreover, in vivo generation of Foxp3(+) iNKT cells was observed in the TGF-beta-rich environment of the murine gut. Foxp3(+) iNKT cells displayed a phenotype similar to that of Foxp3(+) regulatory T cells, and they suppress through a contact-dependent, glucocorticoid-induced TNFR-mediated mechanism. Nevertheless, Foxp3(+) iNKT cells retain distinctive NKT cell characteristics, such as promyelocytic leukemia zinc finger protein expression and preferential homing to the liver following adoptive transfer, where they stably maintained Foxp3 expression. Our data thus unveil an unexpected capacity of iNKT cells to acquire regulatory functions that may contribute to the establishment of immunological tolerance.

Antibody-mediated T-cell reduction or increased levels of chimerism overcome resistance to cyclophosphamide-induced tolerance in NKT-deficient mice

We reported that invariant NKT-cell knockout (iNKT KO) mice are resistant to the induction of intrathymic chimerism and clonal deletion in the cyclophosphamide (CP)-induced tolerance system (CPS). However, another report shows that clonal deletion with chimerism may be intact in iNKT KO recipients in a bone marrow transplantation model. We also reported that pretreatment with anti-Thy1.2 mAb, which reduces the number of T cells and iNKT cells, promotes allograft tolerance across H-2 barriers in the CPS. In this study, we evaluated the efficacy of T-cell depletion in the CPS, and the relationship between the role played by iNKT cells in central tolerance and mixed chimerism. BALB/c (H-2(d)) wild-type, or iNKT KO (Jalpha18(-/-)) mice were pretreated with 20-100 microg of anti-Thy1.2 mAb and given 10(8) donor DBA/2 (H-2(d)) spleen cells on Day 0, and 200 mg/kg CP on Day 2. Pretreatment with T-cell depletion resulted in higher levels of mixed chimerism, increased intrathymic clonal deletion of donor-reactive cells, and the induction of skin graft tolerance in iNKT KO recipients in CPS. This suggests that the high levels of mixed chimerism overcame the resistance to CP-induced tolerance in iNKT KO mice. Consistently, the enhancement of mixed chimerism by injection of tolerant donor spleen cells (SC) rendered iNKT KO recipients susceptible to CP-induced tolerance. These results suggest that iNKT-cell-mediated immunoregulation of central tolerance is evident at low levels of peripheral mixed chimerism in the CPS.

Double negative (CD3+ 4- 8-) TCR alphabeta splenic cells from young NOD mice provide long-lasting protection against type 1 diabetes

BACKGROUND

Double negative CD3(+)4(-)8(-) TCR alphabeta splenic cells (DNCD3) can suppress the immune responses to allo and xenografts, infectious agents, tumors, and some autoimmune disorders. However, little is known about their role in autoimmune diabetes, a disease characterized by the reduction of insulin production subsequent to destruction of pancreatic beta-cells by a polyclonal population of self-reactive T-cells. Herein, we analyzed the function and phenotype of DNCD3 splenic cells in young NOD mice predisposed to several autoimmune disorders among which, the human-like autoimmune diabetes.

METHODOLOGY/PRINCIPAL FINDINGS

DNCD3 splenic cells from young NOD mice (1) provided long-lasting protection against diabetes transfer in NOD/Scid immunodeficient mice, (2) proliferated and differentiated in the spleen and pancreas of NOD/Scid mice and pre-diabetic NOD mice into IL-10-secreting T(R)-1 like cells in a Th2-like environment, and (3) their anti-diabetogenic phenotype is CD3(+)(CD4(-)CD8(-))CD28(+)CD69(+)CD25(low) Foxp3(-) iCTLA-4(-)TCR alphabeta(+) with a predominant Vbeta13 gene usage.

CONCLUSIONS/SIGNIFICANCE

These findings delineate a new T regulatory component in autoimmune diabetes apart from that of NKT and CD4(+)CD25(high) Foxp3(+)T-regulatory cells. DNCD3 splenic cells could be potentially manipulated towards the development of autologous cell therapies in autoimmune diabetes.

Immune cell crosstalk in type 1 diabetes

The development of type 1 diabetes involves a complex interaction between pancreatic beta-cells and cells of both the innate and adaptive immune systems. Analyses of the interactions between natural killer (NK) cells, NKT cells, different dendritic cell populations and T cells have highlighted how these different cell populations can influence the onset of autoimmunity. There is evidence that infection can have either a potentiating or inhibitory role in the development of type 1 diabetes. Interactions between pathogens and cells of the innate immune system, and how this can influence whether T cell activation or tolerance occurs, have been under close scrutiny in recent years. This Review focuses on the nature of this crosstalk between the innate and the adaptive immune responses and how pathogens influence the process.

Emerging roles for B lymphocytes in Type 1 diabetes

Self-reactive B lymphocytes play two main pathological roles in autoimmune diseases: as secretors of autoantibodies and as specialized antigen-presenting cells that present self-components to autoreactive T lymphocytes. In recognition of these roles, recent clinical trials have utilized B-lymphocyte-depleting monoclonal antibodies to treat various autoimmune diseases, with encouraging results in those where humoral autoimmunity is clearly important. Surprisingly, recent results in animal models suggest that B-lymphocyte depletion may also be effective in the treatment of T-lymphocyte-mediated autoimmune diseases, such as Type 1 diabetes (T1D). This article reviews the experimental evidence that has uncovered pathogenic as well as regulatory roles for B lymphocytes in the prodrome of T1D and how this information is being used to develop novel therapeutic strategies to treat the disease.

Alpha-GalCer ameliorates listeriosis by accelerating infiltration of Gr-1+ cells into the liver

Alpha-galactosylceramide (alpha-GalCer) activates invariant (i)NKT cells, which in turn stimulate immunocompetent cells. Although activation of iNKT cells appears critical for regulation of immune responses, it remains elusive whether protection against intracellular bacteria can be induced by alpha-GalCer. Here, we show that alpha-GalCer treatment ameliorates murine listeriosis, and inhibits inflammation following Listeria monocytogenes infection. Liver infiltration of Gr-1+ cells and gamma/delta T cells was accelerated by alpha-GalCer treatment. Gr-1+ cell and gamma/delta T-cell depletion exacerbated listeriosis in alpha-GalCer-treated mice, and this effect was more pronounced after depletion of Gr-1+ cells than that of gamma/delta T cells. Although GM-CSF and IL-17 were secreted by NKT cells after alpha-GalCer treatment, liver infiltration of Gr-1+ cells was not prevented by neutralizing mAb. In parallel to the numerical increase of CD11b+Gr-1+ cells in the liver following alpha-GalCer treatment, CD11b-Gr-1+ cells were numerically reduced in the bone marrow. In addition, respiratory burst in Gr-1+ cells was enhanced by alpha-GalCer treatment. Our results indicate that alpha-GalCer-induced antibacterial immunity is caused, in part, by accelerated infiltration of Gr-1+ cells and to a lesser degree of gamma/delta T cells into the liver. We also suggest that the infiltration of Gr-1+ cells is caused by an accelerated supply from the bone marrow.

CD4+ T cells in sarcoidosis: targets and tools

Activated pulmonary T-helper type 1 lymphocytes are essential for the inflammatory process in sarcoidosis. Both the T cells and their mediators promoting inflammation may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor AV2S3(+) CD4(+) T cells, are found at dramatically increased levels in the bronchoalveolar lavage fluid of a subpopulation of sarcoidosis patients with active disease. This particular T-cell subset may be used as a tool to reveal a sarcoidosis-specific antigen. Recent studies of natural killer T cells and T regulatory cells from patients with sarcoidosis have described abnormalities that may be relevant for the inflammatory process in this disease. These findings are exciting news and may be of help for designing new treatment strategies.

Alpha-galactosylceramide promotes killing of Listeria monocytogenes within the macrophage phagosome through invariant NKT-cell activation

alpha-Galactosylceramide (alpha-GalCer) has been exploited for the treatment of microbial infections. Although amelioration of infection by alpha-GalCer involves invariant natural killer T (iNKT)-cell activation, it remains to be determined whether macrophages (Mphi) participate in the control of microbial pathogens. In the present study, we examined the participation of Mphi in immune intervention in infection by alpha-GalCer using a murine model of listeriosis. Phagocytic and bactericidal activities of peritoneal Mphi from C57BL/6 mice, but not iNKT cell-deficient mice, were enhanced after intraperitoneal injection of alpha-GalCer despite the absence of iNKT cells in the peritoneal cavity. High levels of gamma interferon (IFN-gamma) and nitric oxide (NO) were detected in the peritoneal cavities of mice treated with alpha-GalCer and in culture supernatants of peritoneal Mphi from mice treated with alpha-GalCer, respectively. Although enhanced bactericidal activity of peritoneal Mphi by alpha-GalCer was abrogated by endogenous IFN-gamma neutralization, this was only marginally affected by NO inhibition. Similar results were obtained by using a listeriolysin O-deficient strain of Listeria monocytogenes. Moreover, respiratory burst in Mphi was increased after alpha-GalCer treatment. Our results suggest that amelioration of listeriosis by alpha-GalCer is, in part, caused by enhanced killing of L. monocytogenes within phagosomes of Mphi activated by IFN-gamma from iNKT cells residing in an organ(s) other than the peritoneal cavity.

Regulation of the induction and function of cytotoxic T lymphocytes by natural killer T cell

Cytotoxic T lymphocytes (CTLs) play a crucial role in the infections and the antitumor immunity. Induction and activation of antigen-specific CTLs is an important strategy in immunotherapy for various diseases, and several researchers have focused on the modulation of CTL induction and function. Natural killer T (NKT) cells are an important focus area of researchers studying immunomodulatory responses to tumors and infectious diseases. CD1d-restricted NKT cells consist of type I NKT cells and type II NKT cells. α-galactosylceramide (α-GalCer)-activated type I NKT cells secrete both Th1 (e.g., IFN-γ) and Th2 cytokines, affect the expression of costimulatory molecules in immune cells, and regulate the host immune system. Type II NKT cells, however, are stimulated by sulfatide, a self-glycolipid derived from myelin, and play an immunosuppressive role in animal model of autoimmune diseases. CTL generation, activation, and suppression are strongly affected by activated type I and type II NKT cells. Thus, the regulation of these NKT cells leads to the modification of CTL function. CTLs contribute to antimicrobial responses, antitumor immune and autoimmune responses. Understanding the role of NKT cells in the regulation of CTL generation, activation, and suppression enable the development of novel treatment strategies for these diseases.

Autoreactive natural killer T cells: promoting immune protection and immune tolerance through varied interactions with myeloid antigen-presenting cells

Natural killer T (NKT) cells are innate T lymphocytes that are restricted by CD1d antigen-presenting molecules and recognize lipids and glycolipids as antigens. NKT cells have attracted attention for their potent immunoregulatory effects. Like other types of regulatory lymphocytes, a high proportion of NKT cells appear to be autoreactive to self antigens. Thus, as myeloid antigen-presenting cells (APCs) such as monocytes, dendritic cells (DCs) and myeloid-derived suppressor cells (MDSCs) constitutively express CD1d, NKT cells are able to interact with these APCs not only during times of immune activation but also in immunologically quiescent periods. The interactions of NKT cells with myeloid APCs can have either pro-inflammatory or tolerizing outcomes, and a central question is how the ensuing response is determined. Here we bring together published results from a variety of model systems to highlight three critical factors that influence the outcome of the NKT-APC interaction: (i) the strength of the antigenic signal delivered to the NKT cell, as determined by antigen abundance and/or T-cell receptor (TCR) affinity; (ii) the presence or absence of cytokines that costimulate NKT cells [e.g. interleukin (IL)-12, IL-18 and interferon (IFN)-alpha]; (iii) APC intrinsic factors such as differentiation state (e.g. monocyte versus DC) and Toll-like receptor (TLR) stimulation. Together with recent findings that demonstrate new links between NKT cell activation and endogenous lipid metabolism, these results outline a picture in which the functions of NKT cells are closely attuned to the existing biological context. Thus, NKT cells may actively promote tolerance until a critical level of danger signals arises, at which point they switch to activating pro-inflammatory immune responses.

Human CD1D gene expression is regulated by LEF-1 through distal promoter regulatory elements

CD1d-expressing cells present lipid Ag to CD1d-restricted NKT cells, which play an important role in immune regulation and tumor rejection. Lymphoid enhancer-binding factor-1 (LEF-1) is one of the regulators of the Wnt signaling pathway, which is a powerful regulator in cellular growth, differentiation, and transformation. There is little evidence connecting Wnt signaling to CD1d expression. In this study, we have identified LEF-1 as a regulator of the expression of the gene encoding the human CD1d molecule (CD1D). We found that LEF-1 binds specifically to the CD1D promoter. Overexpression of LEF-1 in K562 or Jurkat cells suppresses CD1D promoter activity and downregulates endogenous CD1D transcripts, whereas knockdown of LEF-1 using LEF-1-specific small interfering RNA increases CD1D transcripts in K562 and Jurkat cells but there are different levels of surface CD1d on these two cell types. Chromatin immunoprecipitation showed that the endogenous LEF-1 is situated at the CD1D promoter and interacts with histone deacetylase-1 to facilitate the transcriptional repressor activity. Knockdown of LEF-1 using small interfering RNA potentiates an acetylation state of histone H3/H4, supporting the notion that LEF-1 acts as a transcriptional repressor for the CD1D gene. Our finding links LEF-1 to CD1D and suggests a role of Wnt signaling in the regulation of the human CD1D gene.

High doses of alpha-galactosylceramide potentiate experimental autoimmune encephalomyelitis by directly enhancing Th17 response

Alpha-galactosylceramide (alpha-GC) is widely known to activate invariant natural killer T (iNKT) cells to suppress myelin antigen-specific Th1 responses, protecting susceptible mice against experimental autoimmune encephalomyelitis (EAE). Here, we demonstrate an unexpected finding that high doses of alpha-GC exacerbated, rather than ameliorated, EAE. Similar results were observed when MOG(35-55)-specific T cells treated with high-dose alpha-GC were transferred into naïve syngeneic recipient mice. Further study showed that high doses of alpha-GC directly enhance the Th17 and Th1 response by activation of CD4(+)CD44(+) memory T cells through phosphorylation of STAT3 and activation of NF-kappaB. Unlike the activation of iNKT cells by low doses of alpha-GC, high doses of alpha-GC directly interacted with CD1d expressed on T cells and activated Th17 and Th1 cells. Furthermore, antigen-presenting cells (APCs) predominantly express CD1d1, whereas the majority of CD4(+) T cells express CD1d2. Knockdown of CD1d1 or CD1d2 gene expression by RNAi interfered with the activation of iNKT or Th17/Th1 cells, respectively. Therefore, alpha-GC treatment could improve or worsen EAE by engaging either APCs or Th17/Th1 cells depending on the dose used.

Therapeutic strategies for diabetes and complications: a role for sphingolipids?

Diabetes is a debilitating chronic disease that has no cure and can only be managed by pharmaceutical or nutritional interventions. Worldwide, the incidence of diabetes and diabetic complications is dramatically increasing. This may reflect the incomplete knowledge base underlying the role of inflammatory or nutritional stresses to exacerbate diabetic complications. Despite the knowledge that hyperlipidemia is a cardinal feature of both Type 1 and 2 diabetes, the actual lipid species that contribute to complications such as diabetic nephropathy, retinopathy, neuropathy and cardiovascular disease have not been well defined, or have not elucidated new treatment strategies. Sphingolipids comprise only a fraction of total lipids but a body of evidence has now identified dysfunctional sphingolipid metabolism and/or generation of specific sphingolipid metabolites as contributors to diabetic complications. This review suggests that pharmacological therapies that target dysfunctional sphingolipid metabolism and/or signaling may prove beneficial in decreasing the chronic pathology of hyperglycemia and hyperlipidemia. Moreover, the review suggests that these treatment options may also prove beneficial to ameliorate or delay pancreatic beta cell failure.

An alpha-galactosylceramide C20:2 N-acyl variant enhances anti-inflammatory and regulatory T cell-independent responses that prevent type 1 diabetes

Protection from type 1 diabetes (T1D), a T helper type 1 (Th1)-mediated disease, is achievable in non-obese diabetic (NOD) mice by treatment with alpha-galactosylceramide (alpha-GalCer) glycolipids that stimulate CD1d-restricted invariant natural killer T (iNK T) cells. While we have reported previously that the C20:2 N-acyl variant of alpha-GalCer elicits a Th2-biased cytokine response and protects NOD mice from T1D more effectively than a form of alpha-GalCer that induces mixed Th1 and Th2 responses, it remained to determine whether this protection is accompanied by heightened anti-inflammatory responses. We show that treatment of NOD mice with C20:2 diminished the activation of 'inflammatory' interleukin (IL)-12 producing CD11c(high)CD8+ myeloid dendritic cells (mDCs) and augmented the function of 'tolerogenic' DCs more effectively than treatment with the prototypical iNKT cell activator KRN7000 (alpha-GalCer C26:0) that induces Th1- and Th2-type responses. These findings correlate with a reduced capacity of C20:2 to sustain the early transactivation of T, B and NK cells. They may also explain our observation that C20:2 activated iNK T cells depend less than KRN7000 activated iNK T cells upon regulation by regulatory T cells for cytokine secretion and protection from T1D. The enhanced anti-inflammatory properties of C20:2 relative to KRN7000 suggest that C20:2 should be evaluated further as a drug to induce iNK T cell-mediated protection from T1D in humans.

The specialized iNKT cell system recognizes glycolipid antigens and bridges the innate and acquired immune systems with potential applications for cancer therapy

Invariant NKT (iNKT) cells bridge innate and acquired immunity and play an important role in both protective and regulatory responses. The nature of the response is dictated by the initial cytokine environment: interaction with IL-10-producing cells induces negative regulatory T(h)2/regulatory T cell-type iNKT cells, while that with IL-12-producing cells results in pro-inflammatory T(h)1-type responses. Particularly, in the anti-tumor response, iNKT cells mediate adjuvant activity by their production of IFN-gamma, which in turn activates both innate and acquired immune systems. Thus, upon activation of iNKT cells, both MHC(-) and MHC(+) tumor cells can be efficiently eliminated. On the basis of these mechanisms, iNKT cell-targeted adjuvant cell therapies have been developed and have shown great promise in initial clinical trials on cancer patients.

A recombinant heavy chain antibody approach blocks ART2 mediated deletion of an iNKT cell population that upon activation inhibits autoimmune diabetes

The ectoenzyme ADP-ribosyltransferase 2.2 (ART2.2) can apoptotically delete various T-cell subsets. Depending on the involved apoptotic T-cell subset, enhanced ART2.2 activity could result in immunosuppression or autoimmunity. Diminished activity of the CD38 ectoenzyme that normally represents a counter-regulatory competitor for the NAD substrate represents one mechanism enhancing ART2.2 activity. Hence, it would be desirable to develop an agent that efficiently blocks ART2.2 activity in vivo. While the llama derived recombinant s+16 single domain antibody overcame the difficulty of specifically targeting the ART2.2 catalytic site potential therapeutic use of this reagent is limited due to short in vivo persistence. Thus, we tested if a modified version of s+16 incorporating the murine IgG1 Fc tail (s+16Fc) mediated long-term efficient in vivo suppression of ART2.2. We reasoned an ideal model to test the s+16Fc reagent were NOD mice in which genetic ablation of CD38 results in an ART2.2 mediated reduction in already sub-normal numbers of immunoregulatory natural killer T-(NKT) cells to a level that no longer allows them when activated by the super-agonist alpha-galactosylceramide (alpha-GalCer) to elicit effects inhibiting autoimmune type 1 diabetes (T1D) development. Treatment with s+16Fc efficiently mediated long-term in vivo inhibition of ART2.2 activity in NOD.CD38(null) mice, restoring their iNKT cell numbers to levels that upon alpha-GalCer activation were capable of inhibiting T1D development.

[Immunological evaluation for CML and its possibility for an immunotherapy]

Chronic myelogenous leukemia (CML) is associated with the Ph1 chromosome translocation, which produces a chimeric tyrosine-specific kinase gene, the product of the fusion of the BCR gene and the ABL gene. The immune system has long been implicated in the control of CML. We found oligoclonal T cell responses in treated patients with IFN-alpha or leukemic dendritic cells. Also other groups treated chronic phase CML (CP-CML) patients with various leukemic antigen peptides, resulted in apparent immune response and clinical response. Imatinib mesylate is currently used as the first line therapy for CP-CML patients. Although it selectively targets the ABL portion of BCR-ABL protein as a reversible tyrosine kinase inhibitor, it cannot kill the leukemic stem cells of CML. To find a possibility to enhance the immunity in imatinib-treated CML patients by combining it with immunotherapy, we summarized the immune response of innate and adaptive immunity in CML. Development of such immunotherapeutic strategies would be a promising approach to treat the imatinib-treated CML-CP patients.

Beta-galactosylceramide alters invariant natural killer T cell function and is effective treatment for lupus

NZB/W female mice spontaneously develop systemic lupus, an autoantibody mediated disease associated with immune complex glomerulonephritis. Natural killer (NK) T cells augment anti-dsDNA antibody secretion by NZB/W B cells in vitro, and blocking NKT cell activation in vivo with anti-CD1 mAb ameliorates lupus disease activity. In the current study, we show that beta-galactosylceramide reduces the in vivo induction of serum IFN-gamma and/or IL-4 by the potent NKT cell agonist alpha-galactosylceramide and reduces NKT cell helper activity for IgG secretion. Treatment of NZB/W mice with the beta-galactosylceramide ameliorated lupus disease activity as judged by improvement in proteinuria, renal histopathology, IgG anti-dsDNA antibody formation, and survival. In conclusion, beta-galactosylceramide, a glycolipid that reduces the cytokine secretion induced by a potent NKT cell agonist ameliorates lupus in NZB/W mice.

Can infections protect against autoimmunity?

PURPOSE OF REVIEW

It has often been suggested that autoimmune diseases are initiated by certain infectious agents that mimic self-antigens or polyclonally activated autoreactive lymphocytes. An alternative, and not necessarily mutually exclusive, hypothesis that some infections might inhibit the onset of some autoimmune conditions has more recently been explored. In this review, the evidence suggesting that the current rise in the incidence of some autoimmune diseases is attributable to a decrease in the incidence of exposure to certain infections will be discussed.

RECENT FINDINGS

Studies using animal models have shown that some infectious agents or products derived from them have the potential to inhibit the onset of autoimmunity. These studies have led to the suggestion that human autoimmune or allergic diseases might be alleviated by the use of microbial products. There are some data that would support such an observation.

SUMMARY

The incidence of some autoimmune diseases has increased dramatically in recent years in the developed world. Many autoimmune diseases are governed by both genetic and environmental factors. Our immune system has coevolved with infectious agents. There have been marked changes in the exposure to certain infectious agents over the last 70 years. It has been proposed that certain infections of historical importance might inhibit the development of autoimmune disorder. This review highlights studies addressing the ways in which infectious agents might inhibit onset of autoimmunity, and how this might lead to the development of novel therapeutic approaches.