Dendritic cells exposed in vitro to TGF-beta1 ameliorate experimental autoimmune myasthenia gravis

Tolerising cellular therapies: what is their promise for autoimmune disease?

The current management of autoimmunity involves the administration of immunosuppressive drugs coupled to symptomatic and functional interventions such as anti-inflammatory therapies and hormone replacement. Given the chronic nature of autoimmunity, however, the ideal therapeutic strategy would be to reinduce self-tolerance before significant tissue damage has accrued. Defects in, or defective regulation of, key immune cells such as regulatory T cells have been documented in several types of human autoimmunity. Consequently, it has been suggested that the administration of ex vivo generated, tolerogenic immune cell populations could provide a tractable therapeutic strategy. Several potentially tolerogenic cellular therapies have been developed in recent years; concurrent advances in cell manufacturing technologies promise scalable, affordable interventions if safety and efficacy can be demonstrated. These therapies include mesenchymal stromal cells, tolerogenic dendritic cells and regulatory T cells. Each has advantages and disadvantages, particularly in terms of the requirement for a bespoke versus an ‘off-the-shelf’ treatment but also their suitability in particular clinical scenarios. In this review, we examine the current evidence for these three types of cellular therapy, in the context of a broader discussion around potential development pathway(s) and their likely future role. A brief overview of preclinical data is followed by a comprehensive discussion of human data.

A Novel Approach to Reinstating Tolerance in Experimental Autoimmune Myasthenia Gravis Using a Targeted Fusion Protein, mCTA1-T146

Reinstating tissue-specific tolerance has attracted much attention as a means to treat autoimmune diseases. However, despite promising results in rodent models of autoimmune diseases, no established tolerogenic therapy is clinically available yet. In the experimental autoimmune myasthenia gravis (EAMG) model several protocols have been reported that induce tolerance against the prime disease-associated antigen, the acetylcholine receptor (AChR) at the neuromuscular junction. Using the whole AChR, the extracellular part or peptides derived from the receptor, investigators have reported variable success with their treatments, though, usually relatively large amounts of antigen has been required. Hence, there is a need for better formulations and strategies to improve on the efficacy of the tolerance-inducing therapies. Here, we report on a novel targeted fusion protein carrying the immunodominant peptide from AChR, mCTA1–T146, which given intranasally in repeated microgram doses strongly suppressed induction as well as ongoing EAMG disease in mice. The results corroborate our previous findings, using the same fusion protein approach, in the collagen-induced arthritis model showing dramatic suppressive effects on Th1 and Th17 autoaggressive CD4 T cells and upregulated regulatory T cell activities with enhanced IL10 production. A suppressive gene signature with upregulated expression of mRNA for TGFβ, IL10, IL27, and Foxp3 was clearly detectable in lymph node and spleen following intranasal treatment with mCTA1–T146. Amelioration of EAMG disease was accompanied by reduced loss of muscle AChR and lower levels of anti-AChR serum antibodies. We believe this targeted highly effective fusion protein mCTA1–T146 is a promising candidate for clinical evaluation in myasthenia gravis patients.

Modulation of CD11c+ lung dendritic cells in respect to TGF-β in experimental pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a deadly, progressive lung disease with very few treatment options till now. Bleomycin-induced pulmonary fibrosis (BIPF) is a commonly used mice model in IPF research. TGF-β1 has been shown to play a key role in pulmonary fibrosis (PF). Dendritic cell (DC) acts as a bridge between innate and adaptive immune systems. The coexistence of chronic inflammation sustained by mature DCs with fibrosis suggests that inflammatory phenomenon has key importance in the pathogenesis of pulmonary fibrosis. Here, we investigated the modulation of DCs phenotypic maturation, accumulation in lung tissue, and expression of other lung DC subsets in respect to TGF-β in PF. First, we established BIPF model in mice and blocked TGF-β expression by the use of inhibitor SB431542. Accumulation of lung CD11c+ DCs is significantly higher in both inflammatory and fibrotic phases of the disease but that percentages got reduced in the absence of TGF-β. TGF-β initiates up-regulation of costimulatory molecules CD86 and CD80 in the inflammatory phases of the disease but not so at fibrotic stage. Expression of lung DC subset CD11c+CD103+ is significantly increased in inflammatory phase and also in fibrotic phase of BIPF. Blocking of TGF-β causes decreased expression of CD11c+CD103+ DCs. Another important lung DC subset CD11c+CD11b+ expression is suppressed by the absence of TGF-β after bleomycin administration. CD11c+CD103+ DCs might have anti-inflammatory as well as anti-fibrotic nature in PF. All these data demonstrate differential modulation of CD11c+ lung DCs by TGF-β in experimental PF.

Animal models of myasthenia gravis: utility and limitations

Myasthenia gravis (MG) is a chronic autoimmune disease caused by the immune attack of the neuromuscular junction. Antibodies directed against the acetylcholine receptor (AChR) induce receptor degradation, complement cascade activation, and postsynaptic membrane destruction, resulting in functional reduction in AChR availability. Besides anti-AChR antibodies, other autoantibodies are known to play pathogenic roles in MG. The experimental autoimmune MG (EAMG) models have been of great help over the years in understanding the pathophysiological role of specific autoantibodies and T helper lymphocytes and in suggesting new therapies for prevention and modulation of the ongoing disease. EAMG can be induced in mice and rats of susceptible strains that show clinical symptoms mimicking the human disease. EAMG models are helpful for studying both the muscle and the immune compartments to evaluate new treatment perspectives. In this review, we concentrate on recent findings on EAMG models, focusing on their utility and limitations.

Dendritic Cell-based Immunotherapy for Rheumatoid Arthritis: from Bench to Bedside

Dendritic cells (DCs) are professional antigen presenting cells, and play an important role in the induction of antigen-specific adaptive immunity. However, some DC populations are involved in immune regulation and immune tolerance. These DC populations are believed to take part in the control of immune exaggeration and immune disorder, and maintain immune homeostasis in the body. Tolerogenic DCs (tolDCs) can be generated in vitro by genetic or pharmacological modification or by controlling the maturation stages of cytokine-derived DCs. These tolDCs have been investigated for the treatment of rheumatoid arthritis (RA) in experimental animal models. In the last decade, several in vitro and in vivo approaches have been translated into clinical trials. As of 2015, three tolDC trials for RA are on the list of ClinicalTrial.gov (www.clinicaltrials.gov). Other trials for RA are in progress and will be listed soon. In this review, we discuss the evolution of tolDC-based immunotherapy for RA and its limitations and future prospects.

Exosomes derived from atorvastatin-modified bone marrow dendritic cells ameliorate experimental autoimmune myasthenia gravis by up-regulated levels of IDO/Treg and partly dependent on FasL/Fas pathway

Background

Previously, we have demonstrated that spleen-derived dendritic cells (DCs) modified with atorvastatin suppressed immune responses of experimental autoimmune myasthenia gravis (EAMG). However, the effects of exosomes derived from atorvastatin-modified bone marrow DCs (BMDCs) (statin-Dex) on EAMG are still unknown.

Methods

Immunophenotypical characterization of exosomes from atorvastatin- and dimethylsulfoxide (DMSO)-modified BMDCs was performed by electron microscopy, flow cytometry, and western blotting. In order to investigate whether statin-DCs-derived exosomes (Dex) could induce immune tolerance in EAMG, we administrated statin-Dex, control-Dex, or phosphate-buffered saline (PBS) into EAMG rats via tail vein injection. The tracking of injected Dex and the effect of statin-Dex injection on endogenous DCs were performed by immunofluorescence and flow cytometry, respectively. The number of Foxp3⁺ cells in thymuses was examined using immunocytochemistry. Treg cells, cytokine secretion, lymphocyte proliferation, cell viability and apoptosis, and the levels of autoantibody were also carried out to evaluate the effect of statin-Dex on EAMG rats. To further investigate the involvement of FasL/Fas in statin-Dex-induced apoptosis, the underlying mechanisms were studied by FasL neutralization assays.

Results

Our data showed that the systemic injection of statin-Dex suppressed the clinical symptoms of EAMG rats. These statin-Dex had immune regulation functions in immune organs, such as the spleen, thymus, and popliteal and inguinal lymph nodes. Furthermore, statin-Dex exerted their immunomodulatory effects in vivo by decreasing the expression of CD80, CD86, and MHC class II on endogenous DCs. Importantly, the therapeutic effects of statin-Dex on EAMG rats were associated with up-regulated levels of indoleamine 2,3-dioxygenase (IDO)/Treg and partly dependent on FasL/Fas pathway, which finally resulted in decreased synthesis of anti-R97–116 IgG, IgG2a, and IgG2b antibodies.

Conclusions

Our data suggest that atorvastatin-induced immature BMDCs are able to secrete tolerogenic Dex, which are involved in the suppression of immune responses in EAMG rats. Importantly, our study provides a novel cell-free approach for the treatment of autoimmune diseases.

DC-Based Immunotherapy Combined with Low-Dose Methotrexate Effective in the Treatment of Advanced CIA in Mice

We have previously demonstrated that semimature dendritic cell- (smDC-) based immunotherapy is effective for the treatment of collagen-induced arthritis (CIA) prior to disease onset. In the present study, we examined the efficacy of combination therapy with smDCs and methotrexate (MTX) in advanced CIA with a score of 2-3. Combination therapy with low-dose MTX and type II collagen- (CII-) pulsed smDCs (CII-smDCs) was more effective in inhibiting disease progression than high or low-dose MTX alone or a combination of high dose MTX and CII-smDCs. The effect of CII-smDCs alone was also comparable to the combination therapy. CD4⁺Foxp3⁺ Treg populations and IL-10 secretion markedly increased, and CII-specific autoreactive T cells decreased in mice treated with CII-smDCs alone or in combination with MTX. Combination therapy reduced the secretion of interferon-γ (IFN-γ) and IL-17 with little influence on the IL-4 secretion in the mixed leukocyte reaction. These results imply that the combination therapy with low-dose MTX and smDCs is effective in controlling advanced CIA by enhancing Treg population and suppresses antigen-specific Th1/Th17 immunity, rather than initiating Th1 to Th2 immune deviation. Our findings provide a better understanding of the DC therapy in combination with MTX for the treatment of patients with rheumatoid arthritis (RA).

Caspase-1 inhibitor ameliorates experimental autoimmune myasthenia gravis by innate dendric cell IL-1-IL-17 pathway

BACKGROUND

IL-1β has been shown to play a pivotal role in autoimmunity. Cysteinyl aspartate-specific proteinase-1 (caspase-1) inhibitor may be an important drug target for autoimmune diseases. However, the effects of caspase-1 inhibitor on myasthenia gravis (MG) remain undefined.

METHODS

To investigate the effects of caspase-1 inhibitor on experimental autoimmune myasthenia gravis (EAMG), an animal model of MG, caspase-1 inhibitor was administered to Lewis rats immunized with region 97-116 of the rat AChR α subunit (R97-116 peptide) in complete Freund's adjuvant. The immunophenotypical characterization by flow cytometry and the levels of autoantibody by ELISA were carried out to evaluate the neuroprotective effect of caspase-1 inhibitor.

RESULTS

We found that caspase-1 inhibitor improved EAMG clinical symptom, which was associated with decreased IL-17 production by CD4+ T cells and γδ T cells, lower affinity of anti-R97-116 peptide IgG. Caspase-1 inhibitor decreased expression of CD80, CD86, and MHC class II on DCs, as well as intracellular IL-1β production from DCs. In addition, caspase-1 inhibitor treatment inhibited R97-116 peptide-specific cell proliferation and decreased follicular helper T cells relating to EAMG development.

CONCLUSIONS

Our results suggest that caspase-1 inhibitor ameliorates experimental autoimmune myasthenia gravis by innate DC IL-1-IL-17 pathway and provides new evidence that caspase-1 is an important drug target in the treatment of MG and other autoimmune diseases.

Standardization of the experimental autoimmune myasthenia gravis (EAMG) model by immunization of rats with Torpedo californica acetylcholine receptors--Recommendations for methods and experimental designs

Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR) is characterized by a chronic, fatigable weakness of voluntary muscles. The production of autoantibodies involves the dysregulation of T cells which provide the environment for the development of autoreactive B cells. The symptoms are caused by destruction of the postsynaptic membrane and degradation of the AChR by IgG autoantibodies, predominantly of the G1 and G3 subclasses. Active immunization of animals with AChR from mammalian muscles, AChR from Torpedo or Electrophorus electric organs, and recombinant or synthetic AChR fragments generates a chronic model of MG, termed experimental autoimmune myasthenia gravis (EAMG). This model covers cellular mechanisms involved in the immune response against the AChR, e.g. antigen presentation, T cell-help and regulation, B cell selection and differentiation into plasma cells. Our aim is to define standard operation procedures and recommendations for the rat EAMG model using purified AChR from the Torpedo californica electric organ, in order to facilitate more rapid translation of preclinical proof of concept or efficacy studies into clinical trials and, ultimately, clinical practice.

Therapeutic potential of atorvastatin-modified dendritic cells in experimental autoimmune neuritis by decreased Th1/Th17 cytokines and up-regulated T regulatory cells and NKR-P1(+) cells

Statins have pleiotropic effects which include anti-inflammatory and immunomodulatory effects. In the present study, dendritic cells treated with atorvastatin (statin-DCs) could be induced into tolerogenic DCs. Administration of these tolerogenic DCs ameliorated clinical symptoms in experimental autoimmune neuritis (EAN), which was associated with reduced number of inflammatory cells in sciatic nerves, inhibited CD4(+) T cells proliferation, down-regulated expression of co-stimulatory molecules (CD80 and CD86) and MHC class II, decreased levels of IFN-γ, TNF-α and IL-17A, increased number of NKR-P1(+) cells (including NK and NKT cells), up-regulated number of Treg cells in lymph node MNC as well as increased Foxp3 expression in the thymus. These data indicated that statin-DCs could develop as a new therapeutic strategy to GBS in the future.

Tolerogenic dendritic cell therapy for rheumatoid arthritis: where are we now?

Dendritic cells with tolerogenic function (tolDC) have become a promising immunotherapeutic tool for reinstating immune tolerance in rheumatoid arthritis (RA) and other autoimmune diseases. The concept underpinning tolDC therapy is that it specifically targets the pathogenic autoimmune response while leaving protective immunity intact. Findings from human in-vitro and mouse in-vivo studies have been translated into the development of clinical grade tolDC for the treatment of autoimmune disorders. Recently, two tolDC trials in RA and type I diabetes have been carried out and other trials are in progress or are imminent. In this review, we provide an update on tolDC therapy, in particular in relation to the treatment of RA, and discuss the challenges and the future perspectives of this new experimental immunotherapy.

Atorvastatin-modified dendritic cells in vitro ameliorate experimental autoimmune myasthenia gravis by up-regulated Treg cells and shifted Th1/Th17 to Th2 cytokines

Conventional therapies for autoimmune diseases produce nonspecific immune suppression, which are usually continued lifelong to maintain disease control, and associated with a variety of adverse effects. In this study, we found that spleen-derived dendritic cells (DCs) from the ongoing experimental autoimmune myasthenia gravis (EAMG) rats can be induced into tolerogenic DCs by atorvastatin in vitro. Administration of these tolerogenic DCs to EAMG rats on days 5 and 13 post immunization (p.i.) resulted in improved clinical symptoms, which were associated with increased numbers of CD4(+)CD25(+) T regulatory (Treg) cells and Foxp3 expression, decreased lymphocyte proliferation among lymph node mononuclear cells (MNC), shifted cytokine profile from Th1/Th17 to Th2 type cytokines, decreased level of anti-R97-116 peptide (region 97-116 of the rat acetylcholine receptor α subunit) IgG antibody in serum. These tolerogenic DCs can migrate to spleen, thymus, popliteal and inguinal lymph nodes after they were injected into the EAMG rats intraperitoneally. Furthermore, these tolerogenic DCs played their immunomodulatory effects in vivo mainly by decreased expression of CD86 and MHC class II on endogenous DCs. All these data provided us a new strategy to treat EAMG and even human myasthenia gravis (MG).

Rnf11-like is a novel component of NF-κB signaling, governing the posterior patterning in the zebrafish embryos

RING finger protein 11 (RNF11) is a novel regulator of immunity and cell survival via ubiquitination process in mammalian cells whereas its vertebrate embryonic roles are undefined. Here, we are reporting the isolation, expression and functional roles of an RNF11 orthologue, Rnf11-like in zebrafish embryos. Zebrafish Rnf11-like is composed of 154 amino acids containing RING-H2-finger domain in the C-terminal region and PY-motif. Spatiotemporal expression patterns of rnf11-like indicate that rnf11-like is expressed maternally and zygotically throughout embryogenesis. However, rnf11-like transcripts are present specifically in the presomatic mesoderm (PSM), and later in the brain and retina. Knock-down of Rnf11-like using rnf11-like-specific morpholino causes cell death and developmental defects in the posterior somites, elevating transcripts of NF-κB target gene, ikk1, a negative regulator of NF-κB signaling. All these findings indicate that Rnf11-like is an essential component of NF-κB signaling pathway for specification of the posterior somites in zebrafish embryos.

Current and emerging treatments for the management of myasthenia gravis

Myasthenia gravis is an autoimmune neuromuscular disorder. There are several treatment options, including symptomatic treatment (acetylcholinesterase inhibitors), short-term immunosuppression (corticosteroids), long-term immunosuppression (azathioprine, cyclosporine, cyclophosphamide, methotrexate, mycophenolate mofetil, rituximab, tacrolimus), rapid acting short-term immunomodulation (intravenous immunoglobulin, plasma exchange), and long-term immunomodulation (thymectomy). This review explores in detail these different treatment options. Potential future treatments are also discussed.

Development of dendritic cell-based immunotherapy for autoimmunity

Dendritic cells are professional antigen-presenting cells that maintain immune tolerance to self-antigens by deleting or controlling the pathogenicity of auto-reactive T-cells. Dendritic cell-based immunotherapies show great promise for the restoration of tolerance in autoimmune disease. Dendritic cells can be modified ex vivo to induce stable tolerogenic function and be used as cellular 'vaccines' or they can be targeted in vivo with sophisticated antigen delivery systems. Tolerogenic dendritic cells induce antigen-specific T-cell tolerance in vivo and have therapeutic effects in animal models of autoimmunity. The current challenge is to bring tolerogenic dendritic cell therapy to the clinic.

Designing the optimal vaccine: the importance of cytokines and dendritic cells

Many vaccines existing today provide strong protection against a wide variety of infectious organisms, and these consist of either live attenuated or inactivated microorganisms. Most of these vaccines were developed empirically and there has not been a clear understanding of the immunological principles that contribute to this success. Recent advances in systems biology are being applied to the study of vaccines in order to determine which immunological parameters are the best predictors of success. New approaches to vaccine development include the identification of peptide epitopes and the manipulation of the immune response to generate the most appropriate response. Vaccines are being developed to prevent and/or treat such conditions as cancer and autoimmunity in addition to infectious diseases. Vaccines targeting this diverse group of diseases may need to elicit very different types of immune responses. Recent advances in our understanding of the functions of dendritic cells (DC) and cytokines in orchestrating qualitatively different immune responses has allowed the design of vaccines that can elicit immune responses appropriate for cancer, autoimmunity or infectious organisms. This review will focus on recent advances in the ways DC and cytokines can be used to develop the most appropriate and effective vaccines.

Current and future immunotherapy in myasthenia gravis

Current therapy for myasthenia gravis is directed towards generalized modulation and suppression of the immune system. These approaches have been extensively studied and are effective in many patients with myasthenia, but at the cost of significant adverse effects due to the global effects on the immune system. Future directions in therapy are geared towards focused immunotherapies that aim to improve outcomes while lessening the burden of side effects. This paper reviews both the current accepted treatments for myasthenia gravis as well as promising targeted therapies in development.

Peripheral induction of tolerance by retinal antigen expression

The contribution of peripheral expression of tissue-specific CNS Ags to the generation of tolerance is uncertain. To study this question, we examined mice transgenic (Tg) for expression of beta-galactosidase (beta gal) on the retinal photoreceptor cell arrestin promoter, in conjunction with TCR Tg mice producing CD4(+) T cells specific for beta gal (beta galTCR). Several strategies were used to test the hypothesis that betagal expressed in the retina supported thymus-independent tolerance and regulatory T cell development. Retinal expression generated an immunoregulatory response that depressed development of immune responses to beta gal following systemic immunization with beta gal. This regulation was transferable to naive mice by CD3(+)4(+)25(+) T cells from naive retinal beta gal(+) donors. Experiments that removed the beta gal(+) retina by enucleation showed that subsequent development of a regulatory response was lost. Adoptive transfer of CD25(-) beta galTCR T cells into retinal beta gal Tg mice on the Rag(-/-) background led to regulatory activity that limited lymphopenia-induced proliferation of beta galTCR T cells in mice with retinal expression of beta gal and inhibited the ear-swelling assay for delayed type hypersensitivity. These results show that retinal expression of very small amounts of a tissue-specific Ag can generate tolerance that includes regulatory T cells.

Dexamethasone/1alpha-25-dihydroxyvitamin D3-treated dendritic cells suppress colitis in the SCID T-cell transfer model

Autoantigen-presenting immunomodulatory dendritic cells (DCs) that are used for adoptive transfer have been shown to be a promising therapy for a number of autoimmune diseases. We have previously demonstrated that enteroantigen-pulsed DCs treated with interleukin-10 (IL-10) can partly protect severe combined immunodeficient (SCID) mice adoptively transferred with CD4+ CD25(-) T cells from the development of wasting disease and colitis. We therefore established an in vitro test that could predict the in vivo function of DCs and improve strategies for the preparation of immunomodulatory DCs in this model. Based on these in vitro findings, we here evaluate three methods for DC generation including short-term and long-term IL-10 exposure or DC exposure to dexamethasone in combination with vitamin D3 (Dex/D3). All DCs resulted in lower CD4+ CD25(-) T-cell enteroantigen-specific responses in vitro, but Dex/D3 DCs had the most prominent effect on T-cell cytokine secretion. In vivo, Dex/D3 DCs most efficiently prevented weight loss and gut pathology upon CD4+ CD25(-) T-cell transfer in SCID mice, although the effect on gut pathology was antigen independent. Our data in the SCID T-cell transfer model illustrate some correlation between in vitro and in vivo DC function and document that prevention of experimental inflammatory bowel disease by transfer of immunosuppressive DCs is possible.

Current management options in myasthenia gravis

Myasthenia gravis has changed from being a frequently fatal condition with a reputation little better than motor neuron disease to a generally treatable condition over the previous century. However, the chronic, largely immunosuppressive treatment comes with the major problems of very slow response and of treatment-induced morbidity and mortality. -Myasthenia gravis is a model autoimmune disease of a model physiologic structure, so is well placed for trials of novel treatments with ramifications for autoimmunity generally. There are also good animal models, so specific approaches to reinduction of tolerance can be tested. Hope of future revolutions in treatment should not hinder efforts to better understand currently available therapies and a concerted approach to ameliorate the side effects of treatment.

Tolerogenic dendritic cells pulsed with enterobacterial extract suppress development of colitis in the severe combined immunodeficiency transfer model

Immunomodulatory dendritic cells (DCs) that induce antigen-specific T-cell tolerance upon in vivo adoptive transfer are promising candidates for immunotherapy of autoimmune diseases. The feasibility of such a strategy has recently proved its efficacy in animal models of allotransplantation and experimental allergic encephalitis, but the effect in inflammatory bowel disease has not yet been demonstrated. In severe combined immunodeficient (SCID) mice, adoptively transferred CD4(+) CD25(-) T cells repopulate the lymphoid tissues and lead to development of chronic colitis characterized by CD4(+) T-cell proliferation against enterobacterial extract in vitro. In this model, we adoptively transferred in-vitro-generated bone-marrow-derived DCs exposed to interleukin-10 (IL-10) and an enterobacterial extract. We show that these cells are CD11c positive with intermediate expression of CD40, CD80 and CD86 and have a diminished secretion of IL-6, IL-12 p40/70, tumour necrosis factor-alpha and keratinocyte-derived chemokine (KC) compared to DCs treated with enterobacterial extract alone. In vivo, these cells prevented weight loss in SCID mice adoptively transferred with CD4(+) CD25(-) T cells, resulted in a lower histopathology colitis score and tended to result in higher serum levels of IL-1alpha, IL-10, IL-12, IL-13, IL-17, KC and monokine induced by interferon-gamma (MIG). These data underscore the potential of using immunomodulatory DCs to control inflammatory bowel disease and demonstrate its potential use in future human therapeutic settings.

TGFbeta-dependent gene expression profile during maturation of dendritic cells

Primary immune response to pathogens involves the maturation of antigen-presenting dendritic cells (DC). Bacterial lipopolysacharride (LPS) is a potent inducer of DC maturation, whereas the transforming growth factor beta (TGFbeta) attenuates much of this process. Here, we analyzed the global gene expression pattern in LPS-treated bone marrow derived DC during inhibition of their maturation process by TGFbeta. Exposure of DC to LPS induces a pronounced cell response, manifested in altered expression of a large number of genes. Interestingly, TGFbeta did not affect most of the LPS responding genes. Nevertheless, analysis identified a subset of genes that did respond to TGFbeta, among them the two inflammatory cytokines interleukin (IL)-12 and IL-18. Expression of IL-12, the major proinflammatory cytokine secreted by mature DC, was downregulated by TGFbeta, whereas the expression level of the proinflammatory cytokine IL-18, known to potentiate the IL-12 effect, was upregulated. Expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) increased in response to TGFbeta, concomitantly with reduced expression of chemokine receptor 7 (CCR7). This finding supports the possibility that TGFbeta-dependent inhibition of CCR7 expression in DC is mediated by PPARgamma.

Myasthenia gravis: past, present, and future

Myasthenia gravis (MG) is an autoimmune syndrome caused by the failure of neuromuscular transmission, which results from the binding of autoantibodies to proteins involved in signaling at the neuromuscular junction (NMJ). These proteins include the nicotinic AChR or, less frequently, a muscle-specific tyrosine kinase (MuSK) involved in AChR clustering. Much is known about the mechanisms that maintain self tolerance and modulate anti-AChR Ab synthesis, AChR clustering, and AChR function as well as those that cause neuromuscular transmission failure upon Ab binding. This insight has led to the development of improved diagnostic methods and to the design of specific immunosuppressive or immunomodulatory treatments.

Immune tolerance and its mechanism induced by adoptive transfer of bone marrow-derived dendritic cells in mice with insulin-dependent diabetes mellitus

AIM: To investigate immune tolerance induced by adoptive transfer of bone marrow-derived dendritic cells (DCs) in mice with type 1 diabetes, and to explore its underlying mechanism.

METHODS: Bone marrow cells from BALB/c mice were used to generate DCs by in vitro co-culturing with cytokines. After identifying the purity of DCs, We injected the cells into BALB/c mice intraperitoneally. The mouse model of type 1 diabetes was established by injecting low dose of streptozotocin (STZ) for 5 consecutive days. The blood glucose was examined once a week. At the end of the 4^th week, all the mice were killed and splenic lymphocytes were collected. After in vitro culturing, the proliferation of lymphocytes was detected by MTT assay, and the proportion of CD4⁺CD25⁺T cells was analyzed by fluorescence activated cell sorter (FACS). The serum levels of cytokines IL-2 and IL-4 were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: The level of blood glucose was decreased significantly after adoptive transfer of DCs in comparison with that in the model controls (8.32 ± 1.05 mmol/L vs 18.36 ± 1.55 mmol/L, P < 0.01). In vitro, the proliferation of splenic lymphocytes was inhibited as compared with that of the model controls (0.264 ± 0.019 vs 0.489 ± 0.012, P < 0.05) while the proportion of CD4⁺CD25⁺ T cells was enhanced to 5.28% (1.56% in the model controls). Adoptive transfer of DCs effectively suppressed the secretion of IL-2 (121 ± 19 ng/L vs 195 ± 32 ng/L, P < 0.05) while elevated the content of IL-4 (187 ± 36 ng/L vs 76 ± 30 ng/L, P < 0.01).

CONCLUSION: Adoptive transfer of bone marrow-derived DCs can induce the immune tolerance to type 1 diabetes in mice, and the mechanism may be related with the production of CD4⁺CD25⁺ T cells and balance between Th1 and Th2 cytokines.

Vaccines against myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease mediated by antibodies to nicotinic acetylcholine receptor (AChR) interfering with the neuromuscular transmission. Experimental autoimmune MG serves as an excellent animal model to study possible therapeutic modalities for MG. This review will focus on the different ways to turn off the autoimmune response to AChR, which results in suppression of myasthenia. This paper will describe the use of fragments or peptides derived from the AChR, antigen-presenting cells and anti-T cell receptor antibodies, and will discuss the underlying mechanisms of action. Finally, the authors propose new promising therapeutic prospects, including treatment based on the modulation of regulatory T cells, which have recently been found to be functionally defective in MG patients.

Salmonella typhimurium infection in nonobese diabetic mice generates immunomodulatory dendritic cells able to prevent type 1 diabetes

Infection, commencing across a wide age range, with a live, attenuated strain of Salmonella typhimurium, will halt the development of type 1 diabetes in the NOD mouse. The protective mechanism appears to involve the regulation of autoreactive T cells in a manner associated with long lasting changes in the innate immune compartment of these mice. We show in this study that autoreactive T cell priming and trafficking are altered in mice that have been infected previously by S. typhimurium. These changes are associated with sustained alterations in patterns of chemokine expression. We find that small numbers of dendritic cells from mice that have been previously infected with, but cleared all trace of a S. typhimurium infection are able to prevent the development of diabetes in the highly synchronized and aggressive cyclophosphamide-induced model. The effects we observe on autoreactive T cell trafficking are recapitulated by the immunomodulatory dendritic cell transfers in the cyclophosphamide model.

Antenatal administration of Rh-immune globulin causes significant increases in the immunomodulatory cytokines transforming growth factor-β and prostaglandin E2

BACKGROUND

Production of specific cytokines in response to administration of Rh-immune globulin (RhIG) was examined to assess the mechanism of inhibition of the anti-D production and prevention of hemolytic disease of the newborn (HDN).

STUDY DESIGN AND METHODS

Plasma levels of 17 different cytokines before and 48 hours after antenatal administration of anti-D were measured in 10 women candidates for prophylaxis with RhIG.

RESULTS

No striking changes were observed in levels of the cytokines interleukin (IL)-1 sRII, IL-12 p40, IL-16, or monocyte chemoattractant protein-1. Levels of IL-4, -5, -10, -13, and -17; macrophage inflammatory protein-1alpha; granulocyte-macrophage-colony-stimulating factor; tumor necrosis factor-beta; and interferon-gamma remained below detection levels both before and after testing. IL-1ra levels, however, showed a slight to moderate decrease in 7 of 10 women after RhIG administration. In contrast, levels of TGF-beta1 increased more than 1.3-fold in 7 of 10 women and more than 2-fold in 4 of 10 women; in 1 instance the increase was more than 5-fold and this woman also had a significant increase in TGF-beta2. In addition to TGF-beta, 5 of 10 women had a modest increase (>1.5-fold) in prostaglandin E2 (PGE2). Analyses of the combined results of the 10 women showed that increases in both TGF-beta1 and PGE2 after RhIG were significant.

CONCLUSION

These results indicate that RhIG prophylaxis can induce higher than baseline levels of two strongly immunomodulatory cytokines, TGF-beta and PGE2. These findings represent one possible mechanism for the inhibition of the primary immune response to the D antigen in women receiving RhIG prophylaxis for prevention of HDN.

Immunoregulation of dendritic cells

The paradigm of tolerogenic/immature versus inflammatory/mature dendritic cells has dominated the recent literature regarding the role of these antigen-presenting cells in mediating immune homeostasis or self-tolerance and response to pathogens, respectively. This issue is further complicated by the identification of distinct subtypes of dendritic cells that exhibit different antigen-presenting cell effector functions. The discovery of pathogen-associated molecular patterns and toll-like receptors provides the mechanistic basis for dendritic cell recognition of specific pathogens and induction of appropriate innate and adaptive immune responses. Only recently has insight been gained into how dendritic cells contribute to establishing and/or maintaining immunological tolerance to self. Soluble and cellular mediators have been reported to effectively regulate the function of dendritic cells by inducing several outcomes ranging from non-inflammatory dendritic cells that lack the ability to induce T lymphocyte activation to dendritic cells that actively suppress T lymphocyte responses. A thorough discussion of these stimuli and their outcomes is essential to understanding the potential for modulating dendritic cell function in the treatment of inflammatory disease conditions.

Prostaglandin D2 affects the differentiation and functions of human dendritic cells: impact on the T cell response

The local environment in which dendritic cells (DC) differentiate is important for the acquisition of their immunostimulatory properties. Since prostaglandin D(2) (PGD(2)), a major prostanoid produced during inflammatory reactions, is involved in the control of immune responses, its effect on the differentiation and functions of human monocyte-derived dendritic cells (MDDC) was studied. We show that DC differentiated in the presence of PGD(2) (PG/DC) have an unusual phenotype, with modifications in the expression of molecules involved in antigen (Ag) capture and presentation, leading to higher endocytic and Ag-processing activities. However, under conditions that necessitated Ag processing and presentation, PG/DC have an impaired ability to stimulate naive T cells, whereas superAg-pulsed DC efficiently promote their proliferation. Upon lipopolysaccharide or TNF-alpha/IL-1beta stimulation, PG/DC phenotypically mature but produce abnormal amounts of immunoregulatory cytokines (decreased IL-12p70/IL-10 ratio). Moreover, mature PG/DC fail to up-regulate the chemokine receptor CCR7 and show an impaired migration towards its ligand CCL19. Finally, PG/DC favor the differentiation of naive T cells toward Th2 cells, an effect dependent on IL-10 and inducible costimulator ligand expression by DC. Most of the herein described effects of PGD(2) on MDDC can be reproduced, usually with a higher efficacy, with a selective D prostanoid receptor (DP)1, but not DP2, agonist. Taken as a whole, these results demonstrate that PGD(2) impacts DC differentiation and functions, and extend the concept that it exerts important roles in immunity.

Immunomodulation by a dual altered peptide ligand of autoreactive responses to the acetylcholine receptor of peripheral blood lymphocytes of patients with myasthenia gravis

Myasthenia gravis (MG) is a T cell-dependent, antibody-mediated autoimmune disease. A dual altered peptide ligand (APL) that is composed of the tandemly arranged two single amino acid analogs of two myasthenogenic peptides was demonstrated to downregulate in vitro and in vivo murine MG associated autoreactive responses. Furthermore, treatment with the dual APL ameliorated the clinical manifestations of an established experimental autoimmune MG in mice. This study was undertaken in order to investigate the ability of the dual APL to immunomodulate MG-associated responses of peripheral blood lymphocytes (PBL) of patients with MG to the native autoantigen acetylcholine receptor (AChR). PBL of 22 of 27 patients with MG tested responded by proliferation to torpedo AChR. The proliferative responses of PBL of 21 of 22 responders were significantly inhibited by the dual APL. The inhibition was specific because a control peptide did not inhibit these proliferative responses. The dual APL also downregulated the levels of the secreted pathogenic cytokine IFN-gamma in supernatants of stimulated PBL of 80% of the tested patients. The latter inhibitions correlated with an upregulated production of the immunosuppressive cytokine, tumor growth factor beta. Thus, the results of our study demonstrate that the dual APL is capable of downregulating in vitro autoreactive responses of patients with MG and suggest that this peptide is a potential candidate for a novel specific treatment of patients with MG.

Rapamycin-treated, alloantigen-pulsed host dendritic cells induce ag-specific T cell regulation and prolong graft survival

Tolerogenic properties of dendritic cells (DC), particularly those in the immature state, and their therapeutic potential are increasingly being recognized. Among several distinct approaches to generate stably immature DC, pharmacologic manipulation stands out as a promising and clinically applicable option. We have shown recently that the immunophilin ligand rapamycin (Rapa) can inhibit DC maturation and their effector functions. Here, we examined the impact of Rapa exposure on subsequent alloantigen (Ag) presentation by myeloid DC via the indirect pathway. Rapa-treated, allogeneic lysate-pulsed host DC (Rapa-DC) were inferior stimulators of syngeneic T cells, compared to lysate-pulsed control DC. Rapa exposure did not block alloAg uptake by DC nor impair their in vivo homing to splenic T cell areas after adoptive transfer. T cells primed by Rapa-treated, alloAg-pulsed DC showed decreased capacity to produce IL-2 and IFNgamma, and were hyporesponsive to subsequent challenge via both the direct and indirect pathways, in an Ag-specific manner. When infused 1 week before transplantation, these Rapa-DC significantly prolonged alloAg-specific heart graft survival. This effect was reversed by systemic IL-2 administration but enhanced by either repeated infusion of the cells or a short post-transplant course of FK506. These therapeutic effects, achieved by targeting both major pathways of allorecognition, provide the basis for a clinically applicable strategy to suppress graft rejection.

17β-estradiol regulates the numbers, endocytosis, stimulative capacity and IL-10 secretion of mouse spleen dendritic cells

The 17beta-estradiol (17beta-E2) is a steroid sex hormone that has a profound influence on the immune cells in inducing the apoptosis of both T and B lymphocytes. In this study, mouse spleen dendritic cells (SDCs) were treated with 17beta-E2 and the numbers, endocytosis, stimulative capacity and cytokine production of SDCs were analysed. The results showed that 17beta-E2 reduced the proliferation and stimulative capacity of SDCs and increased the endocytosis of SDCs in a dose-dependent pattern. 17beta-E2 up-regulated IL-10 mRNA level in SDCs in a dose-dependent manner except for the 24 h time point. These data suggest that 17beta-E2 may regulate the physiological and pathological immune response by reducing the number and stimulation of SDCs, increasing their endocytosis and IL-10 mRNA expression at the same time.

Long-Term Effects of IFN-?, IL-10, and TGF-?-Modulated Dendritic Cells on Immune Response in Lewis Rats

Increasing data have shown that IFN-gamma, IL-10, and TGF-beta-modulated dendritic cells (DC) provide a promising strategy in treatment of experimental allergic encephalomyelitis and experimental autoimmune myasthenia gravis through different manner. To explore the immune response status after long-term application of these cytokine-modulated-DC, Lewis rats were injected subcutaneously into naive DC and IFN-gamma, IL-10, and TGF-beta-modulated DC (i.e., IFN-gamma-DC, IL-10-DC, and TGF-beta-DC) at does of 1 x 10(6) cells/rat every month for continuous 18 months, respectively. No rats suffered from decreased vigor and activity as well as cachectic condition during 18-month observation, and no rats had body-weight loss after 18-month treatment. Exploratory laparectomy did not find any tumor in all rats. IL-10-DC and TGF-beta-DC resulted in lower nonspecific (Con A-induced) and antigen specific (ovalbumin-stimulated) spleen mononuclear cells proliferation, accompanied by lower levels of IFN-gamma, IL-10, and TNF-alpha. On the contrary, IFN-gamma-DC did not suppress cell proliferation and IFN-gamma and IL-10 production except only slightly decreased TNF-alpha levels. These results suggest that IFN-gamma-DC seems to be a more ideal candidate in the treatment of autoimmune diseases without suppressing immune response.

Dendritic cells activate autologous T cells and induce IL-4 and IL-10 production in myasthenia gravis

Dendritic cells (DC), as initiators and orchestrators of immune responses, control both naive and primed T cell responses. Depending on their maturation stage, DC promote immunity or tolerance. Here we investigated (1) the phenotype and cytokine secretion patterns of IL-10-modulated immature DC (IL-10-DC) and lipopolysaccharide (LPS)-driven mature DC (LPS-DC) in comparison with unmodulated immature DC (imDC) and (2) the effects of IL-10-DC, and of LPS-DC, vs. imDC on autologous T cell responses in patients with myasthenia gravis (MG) compared with healthy controls (HC). All three types of DC derived from MG significantly increased the levels of CD4+CD25+ T cells and of their subfraction expressing CD69, when compared to DC derived from HC. IL-10-DC induced production of IL-10 and IL-4 by T cells from MG patients, but only IL-10 production from HC. LPS-DC activated autologous T cells as reflected by augmented CD25, CD69 and CTLA-4 expression on CD4+ T cells, without differences between MG and HC. This was associated with increased production of both Th1 (IFN-gamma) and Th2 (IL-10 and IL-4) cytokines by T cells. These results indicate that DC-induced activation of autologous T cells is more pronounced in MG than in HC. In addition, DC-induced T cell responses in MG vs. HC are more Th2-prone.

Phosphatidylserine regulates the maturation of human dendritic cells

Phosphatidylserine (PS), which is exposed on the surface of apoptotic cells, has been implicated in immune regulation. However, the effects of PS on the maturation and function of dendritic cells (DCs), which play a central role in both immune activation and regulation, have not been described. Large unilamellar liposomes containing PS or phosphatidylcholine were used to model the plasma membrane phospholipid composition of apoptotic and live cells, respectively. PS liposomes inhibited the up-regulation of HLA-ABC, HLA-DR, CD80, CD86, CD40, and CD83, as well as the production of IL-12p70 by human DCs in response to LPS. PS did not affect DC viability directly but predisposed DCs to apoptosis in response to LPS. DCs exposed to PS had diminished capacity to stimulate allogeneic T cell proliferation and to activate IFN-gamma-producing CD4(+) T cells. Exogenous IL-12 restored IFN-gamma production by CD4(+) T cells. Furthermore, activated CTLs proliferated poorly to cognate Ag presented by DCs exposed to PS. Our findings suggest that PS exposure provides a sufficient signal to inhibit DC maturation and to modulate adaptive immune responses.

Interleukin-10-modulated immature dendritic cells control the proinflammatory environment in multiple sclerosis

Multiple sclerosis (MS) is a disabling, inflammatory, demyelinating disease of the central nervous system considered to be mediated by autoreactive T cells. Dendritic cells (DC), being professional antigen-presenting cells, play a pivotal role in the decision between T-cell activation and anergy. It has been suggested that mature DC (mDC) induce immunity, whereas immature DC (imDC) have the potential to induce tolerance. In this study, we investigated the effects of autologous imDC versus autologous mDC on lymphocytes with respect to the expression of functionally important cell-surface molecules and production of cytokines. Our aims were to investigate whether the maturation status of DC differs between MS and healthy controls (HC) and to explore whether the effects of DC on T-cell responses differ between MS and HC. DC were generated from adherent blood mononuclear cells from patients with MS and HC. imDC were obtained by culture with either granulocyte-macrophage colony-stimulating factor (GM-CSF) + interleukin-4 (IL-4) or GM-CSF + IL-4 + IL-10. mDC were obtained by adding lipopolysaccharide to DC cultures. Upon coculture with autologous lymphocytes, mDC activated the autologous T cells as reflected by increased CD25 and cytotoxic T-lymphocyte antigen-4 expression on CD4(+) T cells together with the increased production of both T helper 1 (Th1) (IL-2 and interferon-gamma) and Th2 (IL-10 and IL-4) cytokines. Unmodulated naïve imDC induced the production of only IL-4. An exposure of imDC to IL-10 induced the production of IL-4 as well as IL-10 by autologous lymphocytes. We hypothesize that such imDC are important in controlling the proinflammatory environment in vivo in patients with MS.

The Antigen-Presenting Activity of Fresh, Adult Parenchymal Microglia and Perivascular Cells from Retina

Although several observations show local T cell recognition of retinal Ag, there has been no direct demonstration that the APC were retinal derived, rather than recruited. In this study, CD45(+) cells isolated from immunologically quiescent murine retina were tested in vitro for functional evidence of Ag presentation to naive and Ag-experienced CD4 T cells specific for beta-galactosidase. Because CD45(+) cells from brain have been reported to be efficient APC, they were included for comparison. Measures of activation included changes in CD4, CD25, CD44, CD45RB, CD62L, CD69, caspase-3 activation, CFSE dilution, size, number of cells recovered, and cytokine production. Retinal CD45(+) cells gave no evidence of Ag-dependent TCR ligation in naive T cells, unlike splenic APC and CD45(+) cells from brain, which supported potent responses. Instead, addition of retinal CD45(+) cells to cocultures of naive 3E9 T cells plus splenic APC reduced the yield of activated T cells and cytokine production by limiting T cell activation at early time points. Ag-experienced T cells responded weakly to Ag presented by retinal CD45(+) cells. Activating the retinal cells with IFN-gamma, anti-CD40, or LPS incrementally increased their APC activity. Addition of neutralizing Abs to TGF-beta did not reveal suppressed retinal APC activity. Because retina lacks tissue equivalents of meninges and choroid plexus, rich sources of dendritic cells in brain, cells from retina may better represent the APC activity of fresh, adult CNS parenchymal and perivascular cells. The activity of the retinal CD45(+) cells appears to be directed to limiting T cell responses.

T-cell anergy

Self-reactive T cells that escape negative selection in the thymus must be inactivated in the periphery. Anergy constitutes one means of imposing peripheral tolerance. Anergic T cells are functionally inactivated and unable to initiate a productive response even when antigen is encountered in the presence of full co-stimulation. Recent studies have provided new insights into the mechanisms responsible for the induction and maintenance of T-cell anergy. These studies have helped clarify the nature of the signals that induce tolerance, the cells able to deliver them and the molecular processes that underlie the unresponsive state.

Dendritic cell vaccine design: strategies for eliciting peripheral tolerance as therapy of autoimmune diseases

Dendritic cells (DC), as potent antigen-presenting cells (APC), constitute a complex system of cells that initiate and regulate immune responses that result in two opposite outcomes: immunity or tolerance. The fine regulation of these two distinct functions is not completely understood. After loading with antigen, DC exhibit the properties of both antigen and adjuvant, the functional components of vaccines. For a long time, attention has focused on the exceptional ability of DC as professional APC capable of eliciting T and B cell-mediated responses, and on their potential as immunotherapy in cancer. DC exhibit both heterogeneity and plasticity. On the one hand, distinct DC subsets exhibit distinct functions. On the other hand, DC functions can be altered by the cytokine environment or other factors. There is increasing evidence that DC could be used as a tool to induce peripheral tolerance. Because DC-based immunotherapy in autoimmune diseases depends on tolerogenic DC, discerning markers for tolerogenic DC is of great importance. Immature DC, plasmacytoid DC and interleukin-10-modified DC can mediate immune tolerance by inducing T-cell anergy or T-helper type 2 responses. Several possibilities exist for rational modulation of DC to achieve therapeutic tolerance against autoimmune diseases. The final goal is to create optimal prerequisites to use autologous DC that are prepared from the individual patient with autoimmune disease, to render such DC tolerogenic by exposure in vitro to factors that promote tolerogenicity, and to re-infuse these pretreated DC to the patient in order to treat the ongoing autoimmune disease and prevent its future exacerbation.

Regulation of innate and adaptive immunity by the female sex hormones oestradiol and progesterone

Women mount more vigorous antibody- and cell-mediated immune responses following either infection or vaccination than men. The incidence of most autoimmune diseases is also higher in women than in men; however, during pregnancy many autoimmune diseases go into remission, only to flare again in the early post-partum period. Successful pregnancy requires that the female immune system tolerate the presence of a semi-allogeneic graft for 9 months. Oral contraceptive use can increase susceptibility to certain genital tract infections and sexually transmitted diseases in women. Moreover, treatment of mice and rats with female sex hormones is required to establish animal models of genital tract Chlamydia, Neisseria and Mycoplasma infection. This review describes what is currently known about the effects of the female sex hormones oestradiol and progesterone on innate and adaptive immune responses in order to provide a framework for understanding these sex differences. Data from both human and animal studies will be reviewed.

Dendritic cells, T cell tolerance and therapy of adverse immune reactions

Dendritic cells (DC) are uniquely able to either induce immune responses or to maintain the state of self tolerance. Recent evidence has shown that the ability of DC to induce tolerance in the steady state is critical to the prevention of the autoimmune response. Likewise, DC have been shown to induce several type of regulatory T cells including Th2, Tr1, Ts and NKT cells, depending on the maturation state of the DC and the local microenvironment. DC have been shown to have therapeutic value in models of allograft rejection and autoimmunity, although no success has been reported in allergy. Several strategies, including the use of specific DC subsets, genetic modification of DC and the use of DC at various maturation stages for the treatment of allograft rejection and autoimmune disease are discussed. The challenge for the future use of DC therapy in human disease is to identify the appropriate DC for the proposed therapy; a task made more daunting by the extreme plasticity of DC that has recently been demonstrated. However, the progress achieved to date suggests that these are not insurmountable obstacles and that DC may become a useful therapeutic tool in transplantation and autoimmune disease.

Induction of peripheral tolerance to experimental autoimmune myasthenia gravis by acetylcholine receptor-pulsed dendritic cells

Dendritic cells (DC) are usually regarded as antigen-presenting cells involved in T cell activation, but DC also directly and indirectly affect B cell activation, antibody synthesis, and isotype switch. In the present study, bone marrow (BM)-derived DC from healthy rats were pulsed in vitro with acetylcholine receptor (AChR) and injected subcutaneously into healthy Lewis rats. No clinical signs of the first phase of experimental autoimmune myasthenia gravis (EAMG) were observed during 3 weeks of observation. Upon immunization with AChR and complete Freund's adjuvant, the rats that had received AChR-pulsed DC did not develop clinical EAMG. This tolerance of rats injected with AChR-pulsed DC was associated with reduced expression of B cell-activating factor (BAFF) and by reduced numbers of B cells among splenic mononuclear cells (MNC) compared to rats injected with medium or unpulsed DC. Anti-AChR IgG antibody-secreting cells were decreased, while the ratio of IgG1:IgG2b isotypes was enhanced in rats treated with AChR-pulsed DC compared to control EAMG rats. These results demonstrate that AChR-pulsed DC induce peripheral tolerance to EAMG by possibly inhibiting the expression of BAFF and production of anti-AChR antibodies, providing a possible potential for immunotherapy of antibody-mediated autoimmune diseases.

Dendritic cells in hyperplastic thymuses from patients with myasthenia gravis

To investigate the role of dendritic cells (DCs) in the hyperplastic myasthenia gravis (MG) thymus, we studied the frequency and distribution of three mature DC phenotypes (CD83(+)CD11c(+), CD86(+)CD11c(+), and HLA-DR(+)CD11c(+)) in samples from patients with MG whose symptoms dramatically improved following thymectomy and in non-MG control thymuses. In hyperplastic MG thymuses, mature DCs were much more numerous in nonmedullary areas, such as the subcapsular/outer cortex; around the germinal centers; and in extralobular connective tissue, particularly around blood vessels. Mature DCs strongly coexpressed CD44 and appeared to be components of a CD44-highly positive (CD44(high)) cell population migrating from the vascular system. Furthermore, in the hyperplastic MG thymus, the expression of secondary lymphoid-tissue chemokine (SLC) markedly increased especially around extralobular blood vessels, where the CD44(high) cell population accumulated. These findings suggest that DCs may migrate into the hyperplastic thymus from the vascular system via mechanisms that involve CD44 and SLC. DCs may present self-antigens, thereby promoting the priming and/or boosting of potentially autoreactive T cells against the acetylcholine receptor.