CD1d deficiency exacerbates inflammatory dermatitis in MRL-lpr/lpr mice

A Novel Human Interleukin-23A Overexpressing Mouse Model of Systemic Lupus Erythematosus

OBJECTIVE

Interleukin-23 (IL-23) is a crucial cytokine implicated in chronic inflammation and autoimmunity, associated with various diseases such as psoriasis, psoriatic arthritis, and systemic lupus erythematosus (SLE). This study aimed to create and characterize a transgenic mouse model overexpressing human IL-23A (TghIL-23A), providing a valuable tool for investigating the pathogenic role of human IL-23A and evaluating the efficacy of anti-human IL-23A therapeutics.

METHODS

TghIL-23A mice were generated via microinjection of CBA × C57BL/6 zygotes with a fragment of the human IL23A gene, flanked by its 5'-regulatory sequences and the 3' untranslated region of human β-globin. The TghIL-23A pathology was assessed through hematologic and biochemic analyses, cytokine and antinuclear antibody detection, and histopathologic examination of skin and renal tissues. The response to the anti-human IL-23A therapeutic agent guselkumab was evaluated in groups of eight mixed-sex mice receiving subcutaneous treatment twice weekly for 10 weeks using clinical, biomarker, and histopathologic readouts.

RESULTS

TghIL-23A mice exhibited interactions between human IL-23A and mouse IL-23/IL-12p40 and developed a chronic multiorgan autoimmune disease marked by proteinuria, anti-double-stranded DNA antibodies, severe inflammatory lesions in the skin, and milder phenotypes in the kidneys and lungs. The TghIL-23A pathologic features exhibited significant similarities to those observed in human patients with SLE, and they were reversed following guselkumab treatment.

CONCLUSION

We have generated and characterized a novel genetic mouse model of SLE, providing proof-of-concept for the etiopathogenic role of human IL-23A. This new model has a normal life span and integrates several characteristics of the human disease's complexity and chronicity, making it an attractive preclinical tool for studying IL-23-dependent pathogenic mechanisms and assessing the efficacy of anti-human IL-23A or modeled disease-related therapeutics.

CD1-Restricted T Cells in Inflammatory Skin Diseases

Autoimmunity results from the breaking of immune tolerance, leading to inflammation and pathology. Although well studied in the conventional T-cell field, the role of nonconventional T cells in autoimmunity is less understood. CD1-restricted T cells recognize lipid antigens rather than peptide antigens and have been implicated in various autoimmune skin conditions, including psoriasis and atopic dermatitis. In this review, we will discuss the self-lipids that CD1-restricted T cells recognize and how these T cells become aberrantly regulated in pathogenic skin conditions.

A novel humanized cutaneous lupus erythematosus mouse model mediated by IL-21-induced age-associated B cells

Cutaneous lupus erythematosus (CLE) is a relapsing autoimmune disease, but key elements that drive disease initiation and progression remain elusive. To date, the lack of ideal murine model which resemble human cutaneous lupus makes it extremely challenging for moving mechanistic discoveries and novel therapeutics. Here, we prompt a humanized murine model to develop an inducible rapid-onset murine that performs cutaneous rather than systemic lupus, depending on the successful human immune system reconstruction from active lupus patients and UVB irradiation as for essentially pathogenic triggers. In addition, we demonstrate a newly discovered population of B cell with a unique phenotype, that of the age-associated B cell (ABC, T-bet⁺ CD11b⁺), exhibits B cell clusters in humanized cutaneous lupus. In the response of IL-21 and TLR7/9 signals, recruitment of autoreactive B cells to the position of inflammation with subsequent localized antibody production of IgG2a, IgG2b, IgG3, has the potential to exacerbate ongoing inflammation and thus driving lupus-like autoimmunity in a B-cell-dominant fashion. Overall, our model provides a relevant system for exploring the pathophysiology of cutaneous lupus, a suitable model for drug development, as well as updating a potential role of IL-21 and TLR7/9 to be targeted by biologics.

PD-1H (VISTA)-mediated suppression of autoimmunity in systemic and cutaneous lupus erythematosus

Systemic lupus erythematosus (SLE) and discoid lupus erythematosus (DLE) of the skin are autoimmune diseases characterized by inappropriate immune responses against self-proteins; the key elements that determine disease pathogenesis and progression are largely unknown. Here, we show that mice lacking immune inhibitory receptor VISTA or programmed death-1 homolog (PD-1H KO) on a BALB/c background spontaneously develop cutaneous and systemic autoimmune diseases resembling human lupus. Cutaneous lupus lesions of PD-1H KO mice have clustering of plasmacytoid dendritic cells (pDCs) similar to human DLE. Using mass cytometry, we identified proinflammatory neutrophils as critical early immune infiltrating cells within cutaneous lupus lesions of PD-1H KO mice. We also found that PD-1H is highly expressed on immune cells in human SLE, DLE lesions, and cutaneous lesions of MRL/lpr mice. A PD-1H agonistic monoclonal antibody in MRL/lpr mice reduces cutaneous disease, autoantibodies, inflammatory cytokines, chemokines, and immune cell expansion. Furthermore, PD-1H on both T cells and myeloid cells including neutrophils and pDCs could transmit inhibitory signals, resulting in reduced activation and function, establishing PD-1H as an inhibitory receptor on T cells and myeloid cells. On the basis of these findings, we propose that PD-1H is a critical element in the pathogenesis and progression of lupus, and PD-1H activation could be effective for treatment of systemic and cutaneous lupus.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Fas ligand promotes an inducible TLR-dependent model of cutaneous lupus-like inflammation

Toll-like receptors TLR7 and TLR9 are both implicated in the activation of autoreactive B cells and other cell types associated with systemic lupus erythematosus (SLE) pathogenesis. However, Tlr9-/- autoimmune-prone strains paradoxically develop more severe disease. We have now leveraged the negative regulatory role of TLR9 to develop an inducible rapid-onset murine model of systemic autoimmunity that depends on T cell detection of a membrane-bound OVA fusion protein expressed by MHC class II+ cells, expression of TLR7, expression of the type I IFN receptor, and loss of expression of TLR9. These mice are distinguished by a high frequency of OVA-specific Tbet+, IFN-γ+, and FasL-expressing Th1 cells as well as autoantibody-producing B cells. Unexpectedly, contrary to what occurs in most models of SLE, they also developed skin lesions that are very similar to those of human cutaneous lupus erythematosus (CLE) as far as clinical appearance, histological changes, and gene expression. FasL was a key effector mechanism in the skin, as the transfer of FasL-deficient DO11gld T cells completely failed to elicit overt skin lesions. FasL was also upregulated in human CLE biopsies. Overall, our model provides a relevant system for exploring the pathophysiology of CLE as well as the negative regulatory role of TLR9.

Decreased CD1d level is associated with CD86 over-expression in B cells from systemic lupus erythematosus

The disorder of B cells is one of the hallmarks of systemic lupus erythematosus (SLE). The activation state indicated by CD86 of B cells from SLE is well known, while the defect of regulatory B cells mediated by CD1d is also responsible for the process of SLE. In the present study, we focused on the relationship between B cell activation mediated by CD86 and B cell regulatory function mediated by CD1d. Our results showed that the level of CD1d in B cells was decreased during the early stages of B6.MRLlpr SLE mice and imiquimod-treated (IMQ-treated) mice, while the level of CD86 was significantly increased at the late stage. Moreover, the expression of CD1d showed a significantly negative correlation with CD86 level in B cells from IMQ-treated mice (r = -05741; P = 0.0022), B6.MRLlpr mice (r = -0.7091; P = 0.0268), and SLE patients (r = -0.4125; P = 0.0404). The in vivo and in vitro experiments with splenocytes demonstrated that CD1d signaling pathway could inhibit toll-like receptor 7 (TLR7)-induced CD86 expression of B cells. Further studies showed that this relationship also affected antibody production. Thus, our results confirmed the association of CD1d and CD86 levels in B cells from SLE, and demonstrated the importance to preserve the immunoregulatory function of B cells mediated by CD1d in the progression of SLE.

The Immunology of CD1- and MR1-Restricted T Cells

CD1- and MHC-related molecule-1 (MR1)-restricted T lymphocytes recognize nonpeptidic antigens, such as lipids and small metabolites, and account for a major fraction of circulating and tissue-resident T cells. They represent a readily activated, long-lasting population of effector cells and contribute to the early phases of immune response, orchestrating the function of other cells. This review addresses the main aspects of their immunological functions, including antigen and T cell receptor repertoires, mechanisms of nonpeptidic antigen presentation, and the current evidence for their participation in human and experimental diseases.

CD1d knockout mice exhibit aggravated contact hypersensitivity responses due to reduced interleukin-10 production predominantly by regulatory B cells

Conflicting observations have been reported concerning the role of CD1d-dependent natural killer T (NKT) cells in contact hypersensitivity (CHS), supporting either a disease-promoting or downregulatory function. We studied the role of NKT cells in CHS by comparing the immune response in CD1d knockout (CD1d KO) and wild-type (Wt) mice after contact allergen exposure. For induction of CHS, C57BL/6 CD1d KO mice (n = 6) and C57BL/6 Wt mice (n = 6) were sensitised with 1% (w/v) dinitrochlorobenzene (DNCB) or vehicle for three consecutive days and subsequently challenged with a single dose of 0.5% DNCB (w/v) on the ears fifteen days later. We demonstrate that CD1d KO mice, as compared with Wt littermates, have more pronounced infiltration of mononuclear cells in the skin (29.1% increase; P < 0.001), lower frequencies of interleukin-10(+) B cells (B(regs) ) in the spleen (53.2% decrease; P < 0.05) and peritoneal cavity (80.8% decrease; P < 0.05) and increased production of interferon-γ (3-fold; P < 0.05) after DNCB sensitisation and challenge, which suggests an important regulatory and protective role of CD1d-dependent NKT cells in CHS in our model, at least in part via regulation of IL-10 producing B(regs) .

Langerhans Cells Maintain Local Tissue Tolerance in a Model of Systemic Autoimmune Disease

Systemic autoimmune diseases such as lupus affect multiple organs, usually in a diverse fashion where only certain organs are affected in individual patients. It is unclear whether the "local" immune cells play a role in regulating tissue specificity in relation to disease heterogeneity in systemic autoimmune diseases. In this study, we used skin as a model to determine the role of tissue-resident dendritic cells (DCs) in local and systemic involvement within a systemic lupus disease model. Skin-resident DCs, namely, Langerhans cells (LCs), have been implicated in regulating tolerance or autoimmunity using elegant transgenic models, however, their role in local versus systemic immune regulation is unknown. We demonstrate that although lymphocytes from skin-draining lymph nodes of autoimmune-prone MRL/MpJ-Fas(lpr/lp) (r) (MRL-lpr) mice react spontaneously to a physiological skin self-Ag desmoglein-3, epicutaneous applications of desmoglein-3 induced tolerance that is dependent on LCs. Inducible ablation of LCs in adult preclinical MRL-lpr and MRL/MpJ-Fas(+/+) mice resulted in increased autoantibodies against skin Ags and markedly accelerated lupus dermatitis with increased local macrophage infiltration, but had no effect on systemic autoantibodies such as anti-dsDNA Abs or disease in other organs such as kidneys, lung, and liver. Furthermore, skin-draining lymph nodes of LC-ablated MRL-lpr mice had significantly fewer CD4(+) T cells producing anti-inflammatory cytokine IL-10 than LC-intact controls. These results indicate that a skin-resident DC population regulates local tolerance in systemic lupus and emphasize the importance of the local immune milieu in preventing tissue-specific autoimmunity, yet have no effect on systemic autoimmunity.

Invariant natural killer T cells in lupus patients promote IgG and IgG autoantibody production

IgG autoantibodies, including antibodies to double-stranded DNA (dsDNA), are pathogenic in systemic lupus erythematosus (SLE), but the mechanisms controlling their production are not understood. To assess the role of invariant natural killer T (iNKT) cells in this process, we studied 44 lupus patients. We took advantage of the propensity of PBMCs from patients with active disease to spontaneously secrete IgG in vitro. Despite the rarity of iNKT cells in lupus blood (0.002-0.05% of CD3-positive T cells), antibody blockade of the conserved iNKT TCR or its ligand, CD1d, or selective depletion of iNKT cells, inhibited spontaneous secretion of total IgG and anti-dsDNA IgG by lupus PBMCs. Addition of anti-iNKT or anti-CD1d antibody to PBMC cultures also reduced the frequency of plasma cells, suggesting that lupus iNKT cells induce B-cell maturation. Like fresh iNKT cells, expanded iNKT-cell lines from lupus patients, but not healthy subjects, induced autologous B cells to secrete antibodies, including IgG anti-dsDNA. This activity was inhibited by anti-CD40L antibody, as well as anti-CD1d antibody, confirming a role for CD40L-CD40 and TCR-CD1d interactions in lupus iNKT-cell-mediated help. These results reveal a critical role for iNKT cells in B-cell maturation and autoantibody production in patients with lupus.

OCH ameliorates bone marrow failure in mice via downregulation of T-bet expression

The aim of this study is to evaluate the immune mechanism of OCH in the treatment of AA (also named bone marrow failure, BMF) induced in mice. OCH at a dose of 400 μg/kg was injected intraperitoneally (I.P.) prior to the induction of BMF. Our study showed that the incidence of BMF was 100% in BMF group and 13% in OCH treatment group. Significant higher level of IL-4 and lower level of IFN-γ were observed in OCH group than that in BMF group (P < 0.05) as well as untreated group over BMF (P < 0.05). However, there was no significant difference between OCH and untreated group. Compared with untreated, the expression level of T-bet in OCH and BMF was all significantly higher. However, T-bet expression level was lower in OCH than in BMF. In addition, OCH treatment increased NKT cell fractions of bone marrow and the colonies of CFU-GM. In conclusion, treatment of OCH prior to the induction of BMF could prevent the incidence of BMF possibly through downregulating T-bet expression leading to the transition of immune response from Th1 to Th2, suggesting OCH might be a new therapeutic approach in the treatment of BMF or AA.

Human cytomegalovirus (HCMV) US2 protein interacts with human CD1d (hCD1d) and down-regulates invariant NKT (iNKT) cell activity

To avoid host immune surveillance, human cytomegalovirus (HCMV) encoded endoplasmic reticulum (ER)-membrane glycoprotein US2, which interferes with antigen presenting mechanism of Major histocompatibility complex (MHC) class Ia and class II molecules. However, not many attempts have been made to study the effect of HCMV US2 on the expression of MHC class Ib molecules. In this study, we examined the effect of HCMV US2 on the expression and function of human CD1d (hCD1d), which presents glycolipid antigens to invariant NKT (iNKT) cells. Our results clearly showed that the physiological interaction between ER lumenal domain of HCMV US2 and α3 domain of hCD1d was observed within ER. Compared with mature form of hCD1d, immature form of hCD1d is more susceptible to ubiquitin-dependent proteasomal degradation mediated by HCMV US2. Moreover, the ectopic expression of HCMV US2 leads to the down-modulation of iNKT cell activity without significant change of hCD1d expression. These results will advance our understanding of the function of HCMV US2 in immune evasive mechanisms against anti-viral immunity of iNKT cells.

Intrinsic hyporesponsiveness of invariant natural killer T cells precedes the onset of lupus

Patients with systemic lupus erythematosus (SLE) display reduced numbers and functions of invariant natural killer T (iNK T) cells, which are restored upon treatment with corticosteroids and rituximab. It is unclear whether the iNK T cell insufficiency is a consequence of disease or is a primary abnormality that precedes the onset of disease. To address this, we analysed iNK T cell function at different stages of disease development using the genetically lupus-susceptible NZB × NZW F1 (BWF(1)) model. We found that iNK T cell in-vivo cytokine responses to an iNK T cell ligand α-galactosylceramide (α-GalCer) were lower in BWF(1) mice than in non-autoimmune BALB/c and major histocompatibility complex (MHC)-matched NZB × N/B10.PL F1 mice, although iNK T cell numbers in the periphery were unchanged in BWF(1) mice compared to control mice. Such iNK T cell hyporesponsiveness in BWF(1) mice was detected at a young age long before the animals exhibited any sign of autoimmunity. In-vivo activation of iNK T cells is known to transactivate other immune cells. Such transactivated T and B cell activation markers and/or cytokine responses were also lower in BWF(1) mice than in BALB/c controls. Finally, we show that iNK T cell responses were markedly deficient in the NZB parent but not in NZW parent of BWF(1) mice, suggesting that BWF(1) might inherit the iNK T cell defect from NZB mice. Thus, iNK T cells are functionally insufficient in lupus-prone BWF(1) mice. Such iNK T cell insufficiency precedes the onset of disease and may play a pathogenic role during early stages of disease development in SLE.

The combination of two Sle2 lupus-susceptibility loci and Cdkn2c deficiency leads to T-cell-mediated pathology in B6.Fas(lpr) mice

The NZM2410 Sle2c1 lupus susceptibility locus is responsible for the expansion of the B1a cell compartment, and for the induction of T-cell induced renal and skin pathology on a CD95-deficient (Fas(lpr)) background. We have previously shown that deficiency in the cyclin-dependent kinase inhibitor p18(INK4c) (p18) was responsible for the B1a cell expansion but was not sufficient to account for the pathology in B6.lpr mice. This study was designed to map the additional Sle2c1 loci responsible for autoimmune pathology when co-expressed with CD95 deficiency. The production, fine-mapping and phenotypic characterization of five recombinant intervals indicated that three interacting subloci were responsive for inducting autoimmune pathogenesis in B6.lpr mice. One of these subloci corresponds most likely to p18 deficiency. Another major locus mapping to a 2-Mb region at the telomeric end of Sle2c1 is necessary to both renal and skin pathology. Finally, a third locus centromeric to p18 enhances the severity of lupus nephritis. These results provide new insights into the genetic interactions leading to systemic lupus erythematosus disease presentation, and represent a major step towards the identification of novel susceptibility genes involved in T-cell-mediated organ damage.

Germline deletion of β2 microglobulin or CD1d reduces anti-phospholipid antibody, but increases autoantibodies against non-phospholipid antigens in the NZB/W F1 model of lupus

Introduction

β2-microglobulin (β2m) is required for the surface expression of MHC class I and class I-like proteins such as CD1d, Qa1 and neonatal Fc receptor (FcRn), all of which may impact the development of autoimmunity. Since CD1d is known to bind and present phospholipid antigens to T cells, we asked if the deficiency of β2m or CD1d will impact the development of anti-phospholipid antibodies as compared to other aspects of lupus autoimmunity.

Methods

We introgressed the β2m-null genotype onto the NZB and NZW backgrounds for 12 to 14 generations to generate genetically lupus-susceptible (NZB/NZW)F1 (BWF1) mice that are β2m-deficient (β2m°). Circulating immunoglobulins (Ig), rheumatoid factor (RF), anti-DNA and anti-cardiolipin (anti-CL) antibodies, and renal disease were analyzed in these and CD1d-deficient (CD1d°) BWF1 mice that we had previously generated.

Results

Whereas β2m° BWF1 mice had reduced serum IgG, they had increased mortality, nephritis, serum IgG anti-DNA antibody and RF as compared to heterozygous and wild-type littermates. These effects were recapitulated in CD1d° BWF1 mice, except that they also had increased serum IgG as compared to control littermates. Intriguingly, both β2m° and CD1d° mice had lower serum anti-CL antibody levels than in control littermates. Such CD1d dependence of anti-CL antibody production is not mediated by CD1d/glycolipid-reactive iNKT cells, as these cells reduced the production of RF and anti-DNA antibodies but had no effect on anti-CL antibodies.

Conclusions

We report a novel dichotomous role of β2m and CD1d, whereby these molecules differently regulate autoimmunity against phospholipid versus non-phospholipid autoantigens.

Therapeutic manipulation of natural killer (NK) T cells in autoimmunity: are we close to reality?

T cells reactive to lipids and restricted by major histocompatibility complex (MHC) class I-like molecules represent more than 15% of all lymphocytes in human blood. This heterogeneous population of innate cells includes the invariant natural killer T cells (iNK T), type II NK T cells, CD1a,b,c-restricted T cells and mucosal-associated invariant T (MAIT) cells. These populations are implicated in cancer, infection and autoimmunity. In this review, we focus on the role of these cells in autoimmunity. We summarize data obtained in humans and preclinical models of autoimmune diseases such as primary biliary cirrhosis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, psoriasis and atherosclerosis. We also discuss the promise of NK T cell manipulations: restoration of function, specific activation, depletion and the relevance of these treatments to human autoimmune diseases.

Prevention and treatment of type 1 diabetes mellitus by the manipulation of invariant natural killer T cells

Invariant natural killer T (iNKT) cells are CD1d-restricted T cells with regulatory functions. iNKT cells are numerically and functionally deficient in experimental models of type 1 diabetes mellitus (T1DM). Moreover, various experimental strategies correcting the defect of or stimulating iNKT cells prevent T1DM. Here, we review the data on the role of iNKT cells in the development of T1DM and discuss indications, obstacles and prospects of the use of iNKT cell manipulations in the prevention and treatment of human T1DM.

Modulatory function of invariant natural killer T cells in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease with complex immunological and clinical manifestations. Multiple organ failure in SLE can be caused by immune dysfunction and deposition of autoantibodies. Studies of SLE-susceptible loci and the cellular and humoral immune responses reveal variable aberrations associated with this systemic disease. Invariant natural killer T (iNKT) cells are a unique subset of lymphocytes that control peripheral tolerance. Mounting evidence showing reductions in the proportion and activity of iNKT cells in SLE patients suggests the suppressive role of iNKT cells. Studies using murine lupus models demonstrate that iNKT cells participate in SLE progression by sensing apoptotic cells, regulating immunoglobulin production, and altering the cytokine profile upon activation. However, the dichotomy of iNKT cell actions in murine models implies complicated interactions within the body's milieu. Therefore, application of potential therapy for SLE using glycolipids to regulate iNKT cells should be undertaken cautiously.

Disparate effects of depletion of CD1d-reactive T cells during early versus late stages of disease in a genetically susceptible model of lupus

Some T cells react with lipid antigens bound to antigen-presenting molecule CD1d. Numbers and functions of a subset of such lipid-reactive T cells are reduced in patients with systemic lupus erythematosus (SLE) and their relatives, as well as in genetically susceptible and chemically induced animal models of lupus-like disease. We have reported that the germline deletion of CD1d exacerbates lupus, suggesting a protective role of these cells in the development of lupus. The use of a knockout mouse model in this study, however, did not allow examination of the role of these cells at different stages of disease. Here, we describe an approach to deplete CD1d-dependent T cells, which allowed us to investigate the role of these cells at different stages of disease in genetically lupus-prone NZB/NZW F1 (BWF1) mice. Repeated intravenous injections of large numbers of CD1d-transfected cells resulted in ∼50-75% reduction in these cells, as defined by the expression of CD4, NK1.1 and CD122, and lack of expression of CD62 ligand. TCR γδ (+)NK1.1(+) cells were also reduced in the recipients of CD1d-transfected cells as compared with control recipients. Such depletion of CD1d-reactive T cells in preclinical BWF1 mice resulted in disease acceleration with a significant increase in proteinuria and mortality. In older BWF1 mice having advanced nephritis, however, such depletion of CD1d-reactive T cells resulted in some disease improvement. Taken together, these data as well as our published studies suggest that CD1d-reactive T cells protect against the development of lupus in animal models. However, these cells appear to be unable to suppress established lupus nephritis in these animals, and might even play a disease aggravating role in late stages of disease.

Brief treatment with iNKT cell ligand α-galactosylceramide confers a long-term protection against lupus

CD1d presents glycolipid antigens such as α-galactosylceramide (αGalCer) to invariant natural killer T cells (iNKT). We have reported that activated iNKTs inhibit IL-10-producing autoreactive B cells, while promoting or leaving intact the normal B cell responses, making iNKT modulation an attractive therapeutic modality. Here, we report that a brief treatment of young lupus-prone (NZB/NZW)F1 (BWF1) mice with two injections of αGalCer conferred a long-term protection against lupus. Long-term repeated administrations of αGalCer, however, afforded no clinical benefit. These disparate clinical effects correlated with iNKT responsiveness. While a brief treatment with αGalCer enhanced iNKT responses upon in vitro recall, the long-term αGalCer treatment resulted in reduced iNKT responses in BWF1 mice. The improvement in disease with αGalCer treatment was associated with the reduced IL-10 production. Furthermore, iNKTs directly inhibited IL-10-secreting cells in vivo in reconstituted SCID mice and inhibited IL-10-secreting B cells in vitro in co-cultures. Thus, a brief treatment with a CD1d-binding glycolipid enhances iNKT responses, reduces IL-10 production, and delays the onset of lupus, whereas long-term repeated treatments induce marked iNKT hyporesponsiveness and do not affect disease outcome in BWF1 mice. Identifying glycolipid regimens that can modulate iNKT responsiveness will have important implications for developing iNKT-based therapies for autoimmune diseases.

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.

Sugar-free, glycine-stabilized intravenous immunoglobulin prevents skin but not renal disease in the MRL/lpr mouse model of systemic lupus

Intravenous immunoglobulin (IVIG) has a therapeutic potential in many autoimmune diseases. Based on its immune modulating and complement inhibiting effects, IVIG has been tested in systemic lupus erythematosus (SLE), but due to osmotic tubular injury caused by immunoglobulin-stabilizing sugar components, lupus nephritis had been accelerated in some patients, thus IVIG use in SLE has been abandoned. The availability of non-sugar-stabilized IVIG raised the possible re-evaluation of IVIG for SLE. We investigated high-dose, long-term non-sugar-stabilized IVIG treatment on skin and renal SLE manifestations in the MRL/lpr mouse model. Animals were treated once a week with glycine-stabilized IVIG or saline (0.2 ml/ 10 g BW) from 6 weeks until they were humanely killed at 5 months of age. IVIG diminished macroscopic cutaneous lupus compared with saline treated mice. Histology and complement-3 immunostaining also demonstrated a significant reduction of skin disease after IVIG treatment. However, renal histology and function were similar in both groups. Compared with typical osmotic tubular damage induced by 5% sucrose and 10% maltose (used for IVIG stabilization), we did not observe any osmotic tubular injury in the glycine-stabilized IVIG treated mice. Our data demonstrate a beneficial effect of IVIG on skin lupus without renal side-effects. Deeper understanding of the organ-specific pathomechanism may aid an individualized SLE therapy.

The role of iNKT cells in the immunopathology of systemic lupus erythematosus

An increasing body of evidence suggests that CD1d-restricted invariant natural killer T (iNKT) cells play an important immunoregulatory role in a variety of autoimmune diseases in both humans and mouse models. Their role in systemic lupus erythematosus (SLE), however, is not fully determined, as SLE mouse models have yielded conflicting results demonstrating both a protective function and a pathogenic role. The reduced frequency of iNKT cells in peripheral blood of lupus patients supports the idea of a protective role for these cells in the immunopathology of SLE. Therapeutic approaches using glycolipids provide a promising tool to correct numerical iNKT cell deficiencies and to modulate their function. This review highlights the potential role of iNKT cells in lupus immunopathology and summarizes recent studies concerning iNKT cells in SLE patients, lupus-prone murine models and glycolipid therapy.

Cutting edge: migration of langerhans dendritic cells is impaired in autoimmune dermatitis

Tissue-resident dendritic cells, such as Langerhans cells (LC), normally carry Ags from tissues to lymph nodes to induce immunity to tissue Ags. In this study, we report that LC are reduced in the skin-draining lymph nodes of MRL-Fas(lpr/lpr) and MRL-Fas(+/+) mice that develop T cell-mediated autoimmune skin inflammation as compared with MHC-matched healthy strains. This deficiency of LC in skin-draining lymph nodes is due to a profound impairment of LC migration, resulting in the accumulation of activated LC in the skin. Such a defect in LC migration develops before the onset of skin lesions and correlates with the onset and severity of dermatitis. The reduced, rather than increased, migration of LC from skin to skin-draining lymph nodes represents a novel functional abnormality of LC in autoimmune dermatitis.

Sunlight triggers cutaneous lupus through a CSF-1-dependent mechanism in MRL-Fas(lpr) mice

Sunlight (UVB) triggers cutaneous lupus erythematosus (CLE) and systemic lupus through an unknown mechanism. We tested the hypothesis that UVB triggers CLE through a CSF-1-dependent, macrophage (Mø)-mediated mechanism in MRL-Fas(lpr) mice. By constructing mutant MRL-Fas(lpr) strains expressing varying levels of CSF-1 (high, intermediate, none), and use of an ex vivo gene transfer to deliver CSF-1 intradermally, we determined that CSF-1 induces CLE in lupus-susceptible MRL-Fas(lpr) mice, but not in lupus-resistant BALB/c mice. UVB incites an increase in Møs, apoptosis in the skin, and CLE in MRL-Fas(lpr), but not in CSF-1-deficient MRL-Fas(lpr) mice. Furthermore, UVB did not induce CLE in BALB/c mice. Probing further, UVB stimulates CSF-1 expression by keratinocytes leading to recruitment and activation of Møs that, in turn, release mediators, which induce apoptosis in keratinocytes. Thus, sunlight triggers a CSF-1-dependent, Mø-mediated destructive inflammation in the skin leading to CLE in lupus-susceptible MRL-Fas(lpr) but not lupus-resistant BALB/c mice. Taken together, CSF-1 is envisioned as the match and lupus susceptibility as the tinder leading to CLE.

Long-term administration of IgG2a anti-NK1.1 monoclonal antibody ameliorates lupus-like disease in NZB/W mice in spite of an early worsening induced by an IgG2a-dependent BAFF/BLyS production

The role of natural killer (NK) T cells in the development of lupus-like disease in mice is still controversial. We treated NZB/W mice with anti-NK1.1 monoclonal antibodies (mAbs) and our results revealed that administration of either an irrelevant immunoglobulin G2a (IgG2a) mAb or an IgG2a anti-NK1.1 mAb increased the production of anti-dsDNA antibodies in young NZB/W mice. However, the continuous administration of an anti-NK1.1 mAb protected aged NZB/W mice from glomerular injury, leading to prolonged survival and stabilization of the proteinuria. Conversely, the administration of the control IgG2a mAb led to an aggravation of the lupus-like disease. Augmented titres of anti-dsDNA in NZB/W mice, upon IgG2a administration, correlated with the production of BAFF/BLyS by dendritic, B and T cells. Treatment with an anti-NK1.1 mAb reduced the levels of interleukin-16, produced by T cells, in spleen cell culture supernatants from aged NZB/W. Adoptive transfer of NK T cells from aged to young NZB/W accelerated the production of anti-dsDNA in recipient NZB/W mice, suggesting that NK T cells from aged NZB/W are endowed with a B-cell helper activity. In vitro studies, using purified NK T cells from aged NZB/W, showed that these cells provided helper B-cell activity for the production of anti-dsDNA. We concluded that NK T cells are involved in the progression of lupus-like disease in mature NZB/W mice and that immunoglobulin of the IgG2a isotype has an enhancing effect on antibody synthesis due to the induction of BAFF/BLyS, and therefore have a deleterious effect in the NZB/W mouse physiology.

Autoimmunity stimulated by adoptively transferred dendritic cells is initiated by both alphabeta and gammadelta T cells but does not require MyD88 signaling

Vaccination of nonautoimmune prone mice with syngeneic dendritic cells (DC) readily induces anti-DNA autoantibodies but does not trigger systemic disease. We observed that anti-DNA autoantibody generation absolutely required alphabeta T cells and that gammadelta T cells also contributed to the response, but that regulatory T cells restrained autoantibody production. Although both NZB/W F(1) mice and DC vaccinated C57/BL6 mice produced autoantibodies against dsDNA, vaccinated mice had higher levels of Abs against H1 histone and lower levels of antinucleosome Abs than NZB/W F(1) mice. Despite a 100-fold increase in IL-12 and Th1 skewing to a foreign Ag, OVA, synergistic TLR activation of DC in vitro failed to augment anti-DNA Abs or promote class switching beyond that induced by LPS alone. TLR stimulation was not absolutely required for the initial loss of B cell tolerance because anti-DNA levels were similar when wild-type (WT) or MyD88-deficient DC were used for vaccination or WT and MyD88-deficient recipients were vaccinated with WT DC. In contrast, systemic administration of LPS, augmented anti-DNA Ab levels and promoted class switching, and this response was dependent on donor DC signaling via MyD88. LPS also augmented responses in the MyD88-deficient recipients, suggesting that LPS likely exerts its effects on both transferred DC and host B cells in vivo. These results indicate that both the alphabeta and gammadelta subsets are necessary for promoting autoantibody production by DC vaccination, and that although TLR/MyD88 signaling is not absolutely required for initiation, this pathway does promote augmentation, and Th1-mediated skewing, of anti-DNA autoantibodies.

The biology of NKT cells

Recognized more than a decade ago, NKT cells differentiate from mainstream thymic precursors through instructive signals emanating during TCR engagement by CD1d-expressing cortical thymocytes. Their semi-invariant alphabeta TCRs recognize isoglobotrihexosylceramide, a mammalian glycosphingolipid, as well as microbial alpha-glycuronylceramides found in the cell wall of Gram-negative, lipopolysaccharide-negative bacteria. This dual recognition of self and microbial ligands underlies innate-like antimicrobial functions mediated by CD40L induction and massive Th1 and Th2 cytokine and chemokine release. Through reciprocal activation of NKT cells and dendritic cells, synthetic NKT ligands constitute promising new vaccine adjuvants. NKT cells also regulate a range of immunopathological conditions, but the mechanisms and the ligands involved remain unknown. NKT cell biology has emerged as a new field of research at the frontier between innate and adaptive immunity, providing a powerful model to study fundamental aspects of the cell and structural biology of glycolipid trafficking, processing, and recognition.

Invariant NKT cells and tolerance

Invariant natural killer T (iNKT) cells are innate cells that can bias an immune response toward inflammation or toward a negative regulatory response. iNKT cells can produce cytokines immediately on exposure to activating signals, but the role of iNKT cells in the differentiation of T regulatory (Treg) cells and peripheral tolerance was elucidated only within the past decade. The purpose of this review is to outline the current knowledge of how iNKT cells function in various tolerance paradigms. The roles of iNKT cell in anterior chamber-associated immune deviation (ACAID), oral tolerance, other tolerance systems, and autoimmune diseases is discussed.

Examining the role of CD1d and natural killer T cells in the development of nephritis in a genetically susceptible lupus model

OBJECTIVE

CD1d-reactive invariant natural killer T (iNKT) cells secrete multiple cytokines upon T cell receptor (TCR) engagement and modulate many immune-mediated conditions. The purpose of this study was to examine the role of these cells in the development of autoimmune disease in genetically lupus-prone (NZBxNZW)F1 (BWF1) mice.

METHODS

The CD1d1-null genotype was crossed onto the NZB and NZW backgrounds to establish CD1d1-knockout (CD1d0) BWF1 mice. CD1d0 mice and their wild-type littermates were monitored for the development of nephritis and assessed for cytokine responses to CD1d-restricted glycolipid alpha-galactosylceramide (alphaGalCer), anti-CD3 antibody, and concanavalin A (Con A). Thymus and spleen cells were stained with CD1d tetramers that had been loaded with alphaGalCer or its analog PBS-57 to detect iNKT cells, and the cells were compared between BWF1 mice and class II major histocompatibility complex-matched nonautoimmune strains, including BALB/c, (BALB/cxNZW)F1 (CWF1), and NZW.

RESULTS

CD1d0 BWF1 mice had more severe nephritis than did their wild-type littermates. Although iNKT cells and iNKT cell responses were absent in CD1d0 BWF1 mice, the CD1d0 mice continued to have significant numbers of interferon-gamma-producing NKT-like (CD1d-independent TCRbeta+,NK1.1+ and/or DX5+) cells. CD1d deficiency also influenced cytokine responses by conventional T cells: upon in vitro stimulation of splenocytes with Con A or anti-CD3, type 2 cytokine levels were reduced, whereas type 1 cytokine levels were increased or unchanged in CD1d0 mice as compared with their wild-type littermates. Additionally, numbers of thymic iNKT cells were lower in young wild-type BWF1 mice than in nonautoimmune strains.

CONCLUSION

Germline deletion of CD1d exacerbates lupus in BWF1 mice. This finding, together with reduced thymic iNKT cells in young BWF1 mice as compared with nonautoimmune strains, implies a regulatory role of CD1d and iNKT cells during the development of lupus.

Dissociation of the genetic loci leading to b1a and NKT cell expansions from autoantibody production and renal disease in B6 mice with an introgressed New Zealand Black chromosome 4 interval

Previous mapping studies have linked New Zealand Black (NZB) chromosome 4 to several lupus traits, including autoantibody production, splenomegaly, and glomerulonephritis. To confirm the presence of these traits, our laboratory introgressed homozygous NZB chromosome 4 intervals extending from either 114 to 149 Mb or 32 to 149 Mb onto the lupus-resistant C57BL/6 background (denoted B6.NZBc4S and B6.NZBc4L, respectively). Characterization of aged cohorts revealed that B6.NZBc4L mice exhibited a striking increase in splenic B1a and NKT cells in the absence of high titer autoantibody production and significant renal disease. Tissue-specific expansion of these subsets was also seen in the peritoneum and liver for B1a cells and in the bone marrow for NKT cells. Staining with CD1d tetramers loaded with an alpha-galactosylceramide analog (PBS57) demonstrated that the expanded NKT cell population was mainly CD1d-dependent NKT cells. The lack of both cellular phenotypes in B6.NZBc4S mice demonstrates that the genetic polymorphism(s) that result in these phenotypes are on the proximal region of NZB chromosome 4. This study confirms the presence of a locus that promotes the expansion of B1a cells and newly identifies a region that promotes CD1d-restricted NKT cell expansion on NZB chromosome 4. Taken together, the data indicate that neither an expansion of B1a cells and/nor NKT cells is sufficient to promote autoantibody production and ultimately, renal disease.

Glucocorticoids induce differentiation of a specifically activated, anti-inflammatory subtype of human monocytes

Monocytes and macrophages may either promote or down-regulate inflammatory reactions depending on their state of activation. The effects of glucocorticoids (GCs), the most widely used immunosuppressive drugs, on monocytes are currently not well defined. By analyzing the GC-induced expression pattern in human monocytes by microarray technology, we identified for the first time GC-dependent regulation of 133 genes, including anti-inflammatory molecules such as adenosine A3 receptor, CD1d, and IL-1 receptor II. The results were independently confirmed by real-time polymerase chain reaction (PCR) and flow cytometry. Functional clustering of GC-regulated genes indicated induction of monocytic properties such as phagocytosis and motility as well as repression of adhesion, apoptosis, and oxidative burst. These predictions were confirmed by independent functional assays. GCs up-regulate fMLP receptors and specifically promote chemotaxis to this chemoattractant. Furthermore, GCs promote survival of an anti-inflammatory monocytic phenotype in inflammatory reactions, probably by inhibition of apoptosis because of oxidative stress. GCs limit tissue damage because of induction of antioxidative properties and high capacity for phagocytosis of proinflammatory agents. Thus, GC treatment did not cause a global suppression of monocytic effector functions but results in differentiation of a specific anti-inflammatory phenotype which seems to be actively involved in resolution of inflammatory reactions.

The role of invariant natural killer T cells in lupus and atherogenesis

Systemic lupus erythematosus (SLE) is increasingly recognized as a risk factor for the development of premature atherosclerosis. The inflammatory process in both of these diseases is controlled by a variety of cell types of the innate and adaptive immune systems. Recent studies from several groups, including ours, have revealed a critical role of a unique subset of lymphocytes, termed invariant natural killer T (iNKT) cells, in the development of lupus-like autoimmunity and atherosclerosis in animal models. iNKT cells appear to play complex and divergent roles in the development of SLE and atherosclerosis. Our findings suggest that alterations in iNKT cell functions during the development of SLE may be related to the increased risk of SLE patients to develop atherosclerosis and coronary heart disease. We found that iNKT cell activation with the sponge-derived glycolipid alpha- galactosylceramide generally protects against the development of lupus-like autoimmunity in mice, whereas it exacerbates atherosclerosis. Therefore, while our studies have identified iNKT cells as potential therapeutic targets for SLE, further studies are necessary to design drugs that will avoid the underlying harmful effects of iNKT cell activation on the development of atherosclerosis.

Cellular and molecular mechanisms of regulation of autoantibody production in lupus

The hyperactive interaction between helper T cells and autoimmune B cells in individuals predisposed to systemic lupus erythematosus (SLE) can be interrupted by induction of regulatory and suppressor T cells. Using two strategies-high dose tolerance to an immunoglobulin-derived peptide, and minigene vaccination with DNA encoding T cell epitopes presented by MHC class I molecules-our group has induced at least three types of regulatory/suppressive T cells. They include CD8+ T cells that suppress helper T cells by cytokine secretion, CD8+ T suppressors that kill B cells making anti-DNA antibodies, and peptide-binding CD4+CD25+ regulatory T cells that suppress B cells by direct cell contact. Each of these lymphocyte subsets suppresses anti-DNA antibody production and delays the onset of nephritis in BWF1 lupus-prone mice. Patients with SLE have amino acid sequences similar to those from murine anti-DNA antibodies used in these studies, and at similar locations in the VH regions of anti-DNA immunoglobulins. Therefore, strategies described here might ultimately be useful in therapy of the human disease.

Expression of CD1d in human scalp skin and hair follicles: hair cycle related alterations

BACKGROUND

CD1d belongs to a family of antigen presenting molecules that are structurally and distantly related to the classic major histocompatibility complex class I (MHC I) proteins. However, unlike MHC I molecules, which bind protein antigens, CD1d binds to lipid and glycolipid antigens. CD1d is expressed by cells of lymphoid and myeloid origin, and by cells outside of the lymphoid and myeloid lineages, such as human keratinocytes of psoriatic skin.

AIMS

To investigate whether CD1d is also expressed in sun exposed skin and in the immuno-privileged anagen hair follicle.

MATERIALS/METHODS

CD1d immunoreactivity was studied in human scalp skin and hair follicles of healthy women in situ by immunofluorescent and light microscopic immunohistology. Skin biopsies were obtained from normal human scalp containing mainly anagen VI hair follicles from women (age, 53-57 years) undergoing elective plastic surgery.

RESULTS

CD1d showed strong immunostaining in human scalp skin epidermis, pilosebaceous units, and eccrine glands. In the epidermis, CD1d was strongly expressed by basal and granular keratinocytes. In hair follicles, CD1d was expressed in the epithelial compartment and showed hair cycle related alterations, with an increase in the anagen and a reduction in the catagen and telogen phases.

CONCLUSIONS

These results suggest that CD1d plays a role in human scalp skin immunology and protection against lipid antigen rich infectious microbes. They also raise the question of whether keratinocytes of the immuno-privileged anagen hair follicle can present lipid antigens to natural killer T cells. These data could help provide new strategies for the manipulation of hair related disorders.

Expansion and hyperactivity of CD1d-restricted NKT cells during the progression of systemic lupus erythematosus in (New Zealand Black x New Zealand White)F1 mice

CD1d-restricted NKT cells expressing invariant TCR alpha-chain rearrangements (iNKT cells) have been reported to be deficient in humans with a variety of autoimmune syndromes and in certain strains of autoimmune mice. In addition, injection of mice with alpha-galactosylceramide, a specific glycolipid agonist of iNKT cells, activates these T cells and ameliorates autoimmunity in several different disease models. Thus, deficiency and reduced function in iNKT cells are considered to be risk factors for the development of such diseases. In this study we report that the development of systemic lupus erythematosus in (New Zealand Black (NZB) x New Zealand White (NZW))F(1) mice was paradoxically associated with an expansion and activation of iNKT cells. Although young (NZB x NZW)F(1) mice had normal levels of iNKT cells, these expanded with age and became phenotypically and functionally hyperactive. Activation of iNKT cells in (NZB x NZW)F(1) mice in vivo or in vitro with alpha-galactosylceramide indicated that the immunoregulatory role of iNKT cells varied over time, revealing a marked increase in their potential to contribute to production of IFN-gamma with advancing age and disease progression. This evolution of iNKT cell function during the progression of autoimmunity may have important implications for the mechanism of disease in this model of systemic lupus erythematosus and for the development of therapies using iNKT cell agonists.

SLE: translating lessons from model systems to human disease

Systemic lupus erythematosus (SLE, lupus) results from immune-mediated damage to multiple organs. Its pathogenesis should be viewed as a series of steps, beginning with impaired immune regulation that permits self-reactive T-B-cell activation, which results in the production of autoantibodies. Activated T and B cells then infiltrate tissues, which along with autoantibody and immune complex deposition, triggering local events that ultimately cause organ damage. Although improved understanding of early autoimmune events might open up avenues for disease prevention, future investigations must focus on the mechanisms of end-organ damage in model systems and how to translate this knowledge into human disease. Understanding the mechanisms of each pathogenetic step would provide a rational basis for the development of disease stage-specific diagnostic markers and treatments.

The natural killer T cell ligand alpha-galactosylceramide prevents or promotes pristane-induced lupus in mice

Systemic lupus erythematosus is a systemic autoimmune disease characterized by inflammation in organs such as kidneys and presence of autoantibodies against nuclear antigens. We have previously shown that CD1d deficiency in BALB/c mice exacerbates lupus nephritis and autoantibody production induced by the hydrocarbon oil pristane. Here, we have tested the impact of activating CD1d-restricted natural killer T (NKT) cells on pristane-induced lupus-like autoimmunity in BALB/c and SJL mice. Repeated in vivo treatment of pristane-injected BALB/c mice with the NKT cell ligand alpha-galactosylceramide (alpha-GalCer) prior to the onset of florid disease suppressed proteinuria, in a manner that was dependent on CD1d and IL-4 expression. In sharp contrast, however, similar treatment of pristane-injected SJL mice with alpha-GalCer resulted in increased proteinuria. Consistent with these dichotomous effects of NKT cell activation on the development of lupus-like autoimmunity, NKT cells in BALB/c and SJL/J mice exhibited a mixed Th1/Th2 and a Th1-biased cytokine production profile, respectively. These findings demonstrate that NKT cell activation with alpha-GalCer suppresses or promotes pristane-induced lupus-like autoimmunity in mice, in a strain-dependent manner.

alpha-Galactosylceramide therapy for autoimmune diseases: prospects and obstacles

Autoimmune responses are normally kept in check by immune-tolerance mechanisms, which include regulatory T cells. In recent years, research has focused on the role of a subset of natural killer T (NKT) cells - invariant NKT (iNKT) cells, which are a population of glycolipid-reactive regulatory T cells - in controlling autoimmune responses. Because iNKT cells strongly react with a marine-sponge-derived glycolipid, alpha-galactosylceramide (alpha-GalCer), it has been possible to specifically target and track these cells. As I discuss here, although preclinical studies have shown considerable promise for the development of treatment with alpha-GalCer as a therapeutic modality for autoimmune diseases, several obstacles need to be overcome before moving alpha-GalCer therapy from the bench to the bedside.

Going both ways: immune regulation via CD1d-dependent NKT cells

NKT cells are a unique T lymphocyte sublineage that has been implicated in the regulation of immune responses associated with a broad range of diseases, including autoimmunity, infectious diseases, and cancer. In stark contrast to both conventional T lymphocytes and other types of Tregs, NKT cells are reactive to the nonclassical class I antigen-presenting molecule CD1d, and they recognize glycolipid antigens rather than peptides. Moreover, they can either up- or downregulate immune responses by promoting the secretion of Th1, Th2, or immune regulatory cytokines. This review will explore the diverse influences of these cells in various disease models, their ability to suppress or enhance immunity, and the potential for manipulating these cells as a novel form of immunotherapy.

Going both ways: immune regulation via CD1d-dependent NKT cells

NKT cells are a unique T lymphocyte sublineage that has been implicated in the regulation of immune responses associated with a broad range of diseases, including autoimmunity, infectious diseases, and cancer. In stark contrast to both conventional T lymphocytes and other types of Tregs, NKT cells are reactive to the nonclassical class I antigen-presenting molecule CD1d, and they recognize glycolipid antigens rather than peptides. Moreover, they can either up- or downregulate immune responses by promoting the secretion of Th1, Th2, or immune regulatory cytokines. This review will explore the diverse influences of these cells in various disease models, their ability to suppress or enhance immunity, and the potential for manipulating these cells as a novel form of immunotherapy.

Development of Canine Systemic Lupus Erythematosus Model

The purpose of this study was to develop a model for canine systemic lupus erythematosus. Systemic lupus erythematosus (SLE) is a systemic autoimmune syndrome defined by clinical and serological features, including arthritis, glomerulonephritis, dermatitis and autoantibodies. SLE was induced in eight normal dogs by immunization with heparan sulphate, the major glycosaminoglycan of the glomerular basement membrane. All the heparan sulphate-immunized dogs showed mild-to-moderate levels of proteinuria and skin disease. Cutaneous signs associated with SLE including alopecia, erythema, crusting, scaling and seborrhoea were observed. Immunohistological examination of the skin lesions revealed deposition of immunoglobulin M and complement in the dermal-epidermal junction. Three of eight dogs showed lameness. The antinuclear antibody tests were positive with the antibody titres higher than 1:128. Therefore, this experimental SLE model could be useful for studying immune-mediated skin disease and autoimmunity.