Bystander-mediated stimulation of proteolipid protein-specific regulatory T (Treg) cells confers protection against experimental autoimmune encephalomyelitis (EAE) via TGF-β

Remyelination in multiple sclerosis, along with its immunology and association with gut dysbiosis, lifestyle, and environmental factors

Multiple sclerosis (MS) is a chronic inflammatory disease that damages the myelin sheath around the axons of the central nervous system. While there are periods of inflammation and remyelination in MS, the latter can sometimes be insufficient and lead to the formation of lesions in the brain and spinal cord. Environmental factors such as vitamin D deficiency, viral or bacterial infections, tobacco smoking, and anxiety have been shown to play a role in the development of MS. Dysbiosis, where the composition of the microbiome changes, may also be involved in the pathogenesis of MS by affecting the gut's microbial population and negatively impacting the integrity of the epithelia. While the cause of MS remains unknown, genetic susceptibility, and immunological dysregulation are believed to play a key role in the development of the disease. Further research is needed to fully understand the complex interplay between genetic, environmental, and microbial factors in the pathogenesis of MS.

Gut Microbial Metabolome and Dysbiosis in Neurodegenerative Diseases: Psychobiotics and Fecal Microbiota Transplantation as a Therapeutic Approach-A Comprehensive Narrative Review

The comprehensive narrative review conducted in this study delves into the mechanisms of communication and action at the molecular level in the human organism. The review addresses the complex mechanism involved in the microbiota-gut-brain axis as well as the implications of alterations in the microbial composition of patients with neurodegenerative diseases. The pathophysiology of neurodegenerative diseases with neuronal loss or death is analyzed, as well as the mechanisms of action of the main metabolites involved in the bidirectional communication through the microbiota-gut-brain axis. In addition, interventions targeting gut microbiota restructuring through fecal microbiota transplantation and the use of psychobiotics-pre- and pro-biotics-are evaluated as an opportunity to reduce the symptomatology associated with neurodegeneration in these pathologies. This review provides valuable information and facilitates a better understanding of the neurobiological mechanisms to be addressed in the treatment of neurodegenerative diseases.

The immunomodulatory roles of the gut microbiome in autoimmune diseases of the central nervous system: Multiple sclerosis as a model

The gut-associated lymphoid tissue is a primary activation site for immune responses to infection and immunomodulation. Experimental evidence using animal disease models suggests that specific gut microbes significantly regulate inflammation and immunoregulatory pathways. Furthermore, recent clinical findings indicate that gut microbes' composition, collectively named gut microbiota, is altered under disease state. This review focuses on the functional mechanisms by which gut microbes promote immunomodulatory responses that could be relevant in balancing inflammation associated with autoimmunity in the central nervous system. We also propose therapeutic interventions that target the composition of the gut microbiota as immunomodulatory mechanisms to control neuroinflammation.

Engineering live attenuated vaccines: Old dogs learning new tricks

Autoimmune diseases such as rheumatoid arthritis and type 1 diabetes are increasingly common global problems. Concerns about increases in the prevalence of such diseases and the limited efficacy of conventional treatment regimens necessitates new therapies to address these challenges. Autoimmune disease severity and dysbiosis are interconnected. Although probiotics have been established as a therapy to rebalance the microbiome and suppress autoimmune symptoms, these microbes tend to lack a number of advantageous qualities found in non-commensal bacteria. Through attenuation and genetic manipulation, these non-commensal bacteria have been engineered into recombinant forms that offer malleable platforms capable of addressing the immune imbalances found in RA and T1D. Such bacteria have been engineered to express valuable gene products known to suppress autoimmunity such as anti-inflammatory cytokines, autoantigens, and enzymes synthesizing microbial metabolites. This review will highlight current and emerging trends in the field and discuss how they may be used to prevent and control autoimmune diseases.

Oral probiotic promotes indoleamine 2,3-dioxygenase- and TGF-β-Producing plasmacytoid dendritic cells to initiate protection against type 1 diabetes

Colonization factor antigen I (CFA/I) fimbria, an adhesin from enterotoxigenic Escherichia coli, confers protection in murine autoimmune models for type 1 diabetes (T1D), multiple sclerosis, and rheumatoid arthritis. Although CFA/I fimbriae's initial mode of action is in a bystander or in an antigen (Ag)-independent fashion, protection is ultimately dependent upon the induction and/or activation of auto-Ag-specific regulatory T cells (Tregs). However, little is known about how protection transitions from bystander suppression to Ag-specific Tregs. Since dendritic cells (DCs) play an integral role in fate decisions for T cells becoming inflammatory or tolerogenic, the described study tests the hypothesis that Lactococcus lactis expressing CFA/I (LL-CFA/I) stimulates DCs to establish a regulatory microenvironment. To this end, bone marrow-derived dendritic cells (BMDCs) were infected in vitro with LL-CFA/I. Results revealed increased production of IL-10, TGF-β, and indoleamine 2,3-deoxygenase (IDO). Although co-culture of LL-CFA/I infected BMDCs with naïve T cells did not promote Foxp3 expression, TNF-α and IFN-γ production was suppressed. NOD mice orally dosed with LL-CFA/I showed an increase in regulatory plasmacytoid DCs (pDCs) expressing IDO and TGF-β in pancreatic lymph nodes (PaLNs) and spleen three days post-treatment. However, Tregs did not appear in the mucosal inductive sites until much later. These findings show that LL-CFA/I influences specific DC populations to establish tolerance.

Nutritional and ecological perspectives of the interrelationships between diet and the gut microbiome in multiple sclerosis: Insights from marmosets

Studies in experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis, have shown potential links between diet components, microbiome composition, and modulation of immune responses. In this review, we reanalyze and discuss findings in an outbred marmoset EAE model in which a yogurt-based dietary supplement decreased disease frequency and severity. We show that although diet has detectable effects on the fecal microbiome, microbiome changes are more strongly associated with the EAE development. Using an ecological framework, we further show that the dominant factors influencing the gut microbiota were marmoset sibling pair and experimental time point. These findings emphasize challenges in assigning cause-and-effect relationships in studies of diet-microbiome-host interactions and differentiating the diet effects from other environmental, stochastic, and host-related factors. We advocate for animal experiments to be designed to allow causal inferences of the microbiota's role in pathology while considering the complex ecological processes that shape microbial communities.

Thymic atrophy creates holes in Treg-mediated immuno-regulation via impairment of an antigen-specific clone

Age-related thymic atrophy results in reduced output of naïve conventional T (Tcon) cells. However, its impact on regulatory T (Treg) cells is insufficiently understood. Given evidence that thymic Treg (tTreg) cell generation is enhanced in the aged, atrophy thymus and that the aged periphery accumulates peripheral Treg (pTreg) cells, we asked why these Treg cells are unable to effectively attenuate increased autoreactivity-induced chronic inflammation in the elderly. We designed a mock-self-antigen chimera mouse model, in which membrane-bound ovalbumin (mOVA) transgenic mice, bearing a FoxN1-floxed gene for induction of conditional thymic atrophy, received OVA-specific (OT-II) T-cell receptor (TCR) transgenic progenitor cells. The chimeric mice with thymic atrophy exhibited a significant decrease in OVA-specific tTreg and pTreg cells but not polyclonal (pan)-Treg cells. These OVA-specific pTreg cells were significantly less able to suppress OVA-specific stimulation-induced proliferation in vitro and exhibited lower FoxP3 expression. Additionally, we conducted preliminary TCR repertoire diversity sequencing for Treg cells among recent thymic emigrants (RTEs) from Rag^GFP -FoxP3^RFP dual-reporter mice and observed a trend for decreased diversity in mice with thymic atrophy compared to littermates with normal thymus. These data indicate that although the effects of age-related thymic atrophy do not affect pan-Treg generation, certain tissue-specific Treg clones may experience abnormal agonist selection. This, combined with enhanced pan-pTreg cells, may greatly contribute to age-related chronic inflammation, even in the absence of acute autoimmune disease in the elderly.

Oral therapy with colonization factor antigen I prevents development of type 1 diabetes in Non-obese Diabetic mice

Antigen (Ag)-specific tolerization prevents type 1 diabetes (T1D) in non-obese diabetic (NOD) mice but proved less effective in humans. Several auto-Ags are fundamental to disease development, suggesting T1D etiology is heterogeneous and may limit the effectiveness of Ag-specific therapies to distinct disease endotypes. Colonization factor antigen I (CFA/I) fimbriae from Escherichia coli can inhibit autoimmune diseases in murine models by inducing bystander tolerance. To test if Ag-independent stimulation of regulatory T cells (Tregs) can prevent T1D onset, groups of NOD mice were orally treated with Lactococcus lactis (LL) expressing CFA/I. LL-CFA/I treatment beginning at 6 weeks of age reduced disease incidence by 50% (p < 0.05) and increased splenic Tregs producing both IL-10 and IFN-γ 8-fold (p < 0.005) compared to LL-vehicle treated controls. To further describe the role of these Tregs in preventing T1D, protective phenotypes were examined at different time-points. LL-CFA/I treatment suppressed splenic TNF-α⁺CD8⁺ T cells 6-fold at 11 weeks (p < 0.005) and promoted a distinct microbiome. At 17 weeks, IFN-γ⁺CD4⁺ T cells were suppressed 10-fold (p < 0.005), and at 30 weeks, pancreatic Tbet⁺CD4⁺ T cells were suppressed (p < 0.05). These results show oral delivery of modified commensal organisms, such as LL-CFA/I, may be harnessed to restrict Th1 cell-mediated immunity and protect against T1D.

Neuroimmunological Implications of Subclinical Lipopolysaccharide from Salmonella Enteritidis

Mounting evidence has indicated that lipopolysaccharide (LPS) is implicated in neuroimmunological responses, but the body’s response to subclinical doses of bacterial endotoxin remains poorly understood. The influence of a low single dose of LPS from Salmonella Enteritidis, which does not result in any clinical symptoms of intoxication (subclinical lipopolysaccharide), on selected cells and signal molecules of the neuroimmune system was tested. Five juvenile crossbred female pigs were intravenously injected with LPS from S. Enteritidis (5 μg/kg body weight (b.w.)), while five pigs from the control group received sodium chloride in the same way. Our data demonstrated that subclinical LPS from S. Enteritidis increased levels of dopamine in the brain and neuropeptides such as substance P (SP), galanin (GAL), neuropeptide Y (NPY), and active intestinal peptide (VIP) in the cervical lymph nodes with serum hyperhaptoglobinaemia and reduction of plasma CD4 and CD8 T-lymphocytes seven days after lipopolysaccharide administration. CD4 and CD8 T-lymphocytes from the cervical lymph node and serum interleukin-6 and tumour necrosis factor α showed no significant differences between the control and lipopolysaccharide groups. Subclinical lipopolysaccharide from S. Enteritidis can affect cells and signal molecules of the neuroimmune system. The presence of subclinical lipopolysaccharide from S. Enteritidis is associated with unknown prolonged consequences and may require eradication and a deeper search into the asymptomatic carrier state of Salmonella spp.

Gut Microbiota in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis: Current Applications and Future Perspectives

The gut environment and gut microbiome dysbiosis have been demonstrated to significantly influence a range of disorders in humans, including obesity, diabetes, rheumatoid arthritis, and multiple sclerosis (MS). MS is an autoimmune disease affecting the central nervous system (CNS). The etiology of MS is not clear, and it should involve both genetic and extrinsic factors. The extrinsic factors responsible for predisposition to MS remain elusive. Recent studies on MS and its animal model, experimental autoimmune encephalomyelitis (EAE), have found that gastrointestinal microbiota may play an important role in the pathogenesis of MS/EAE. Thus, gut microbiome adjustment may be a future direction of treatment in MS. In this review, we discuss the characteristics of the gut microbiota, the connection between the brain and the gut, and the changes in gut microbiota in MS/EAE, and we explore the possibility of applying microbiota therapies in patients with MS.

Role of intestinal microbiota in the development of multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a demyelinating disease that affects young adults; in that age group, it represents the second leading cause of disability in our setting. Its precise aetiology has not been elucidated, but it is widely accepted to occur in genetically predisposed patients who are exposed to certain environmental factors. The discovery of the regulatory role played by intestinal microbiota in various autoimmune diseases has opened a new line of research in this field, which is discussed in this review.

DEVELOPMENT

We reviewed published studies on the role of the microbiota in the development of both MS and its animal model, experimental autoimmune encephalomyelitis (EAE). In mice, it has been shown that intestinal microorganisms regulate the polarisation of T helper cells from Th1-Th17 up to Th2, the function of regulatory T cells, and the activity of B cells; they participate in the pathogenesis of EAE and contribute to its prevention and treatment. In contrast, evidence in humans is still scarce and mainly based on case-control studies that point to the presence of differences in certain bacterial communities.

CONCLUSIONS

Multiple evidence points to the role of microbiota in EAE. Extrapolation of these results to MS is still in the early stages of research, and studies are needed to define which bacterial populations are associated with MS, the role they play in pathogenesis, and the therapeutic possibilities this knowledge offers us.

Oral administration of apple condensed tannins delays rheumatoid arthritis development in mice via downregulation of T helper 17 (Th17) cell responses

Apples are known to contain high concentrations of phenolic compounds such as condensed tannins. Consumption of condensed tannins has been reported to reduce the risk of many types of chronic diseases including allergies. However, their therapeutic effectiveness and potential in treating autoimmune disease remain controversial. Here, the effect of oral administration of apple condensed tannins (ACT) prepared from apples (Malus pumila cv. Fuji) on bovine type II collagen (CII)-induced arthritis in DBA1/J mice, a well-established murine model of human rheumatoid arthritis (RA), was evaluated. As compared to the control (without ACT administration) group, RA development was delayed and a significant reduction in the RA clinical score was observed in the ACT-administered group. Using cultured splenocytes isolated from CII-immunized mice, ACT-administration was shown to decrease the CII-induced increases in IL-17 expression and production in vitro. We propose that downregulation of T helper (Th) 17 cells is responsible for the ACT-induced RA suppression.

Gut commensalism, cytokines, and central nervous system demyelination

There is increasing support for the importance of risk factors such as genetic makeup, obesity, smoking, vitamin D insufficiency, and antibiotic exposure contributing to the development of autoimmune diseases, including human multiple sclerosis (MS). Perhaps the greatest environmental risk factor associated with the development of immune-mediated conditions is the gut microbiome. Microbial and helminthic agents are active participants in shaping the immune systems of their hosts. This concept is continually reinforced by studies in the burgeoning area of commensal-mediated immunomodulation. The clinical importance of these findings for MS is suggested by both their participation in disease and, perhaps of greater clinical importance, attenuation of disease severity. Observations made in murine models of central nervous system demyelinating disease and a limited number of small studies in human MS suggest that immune homeostasis within the gut microbiome may be of paramount importance in maintaining a disease-free state. This review describes three immunological factors associated with the gut microbiome that are central to cytokine network activities in MS pathogenesis: T helper cell polarization, T regulatory cell function, and B cell activity. Comparisons are drawn between the regulatory mechanisms attributed to first-line therapies and those described in commensal-mediated amelioration of central nervous system demyelination.

The gut microbiome in multiple sclerosis

OPINION STATEMENT

The gut microbiome is made up of a wide range of (chiefly) bacterial species that colonize the small and large intestine. The human gut microbiome contains a subset of thousands of bacterial species, with up to 10(14) total bacteria. Studies examining this bacterial content have shown wide variations in which species are present between individuals. The gut microbiome has been shown to have profound effects on the development and maintenance of immune system in both animal models and in humans. A growing body of evidence has implicated the human gut microbiome in a range of disorders, including obesity, inflammatory bowel diseases, and cardiovascular disease. Animal studies present compelling evidence that the gut microbiome plays a significant role in the progression of demyelinating disease, and that modulation of the microbiome can lead to either exacerbation or amelioration of symptoms. Differences in diet, vitamin D insufficiency, smoking, and alcohol use have all been implicated as risk factors in MS, and all have the ability to affect the composition of the gut microbiota. Preliminary clinical trials aimed at modulating the gut microbiota in MS patients are underway and may prove to be a promising and lower-risk treatment option in the future.

Gut microbiome and the risk factors in central nervous system autoimmunity

Humans are colonized after birth by microbial organisms that form a heterogeneous community, collectively termed microbiota. The genomic pool of this macro-community is named microbiome. The gut microbiota is essential for the complete development of the immune system, representing a binary network in which the microbiota interact with the host providing important immune and physiologic function and conversely the bacteria protect themselves from host immune defense. Alterations in the balance of the gut microbiome due to a combination of environmental and genetic factors can now be associated with detrimental or protective effects in experimental autoimmune diseases. These gut microbiome alterations can unbalance the gastrointestinal immune responses and influence distal effector sites leading to CNS disease including both demyelination and affective disorders. The current range of risk factors for MS includes genetic makeup and environmental elements. Of interest to this review is the consistency between this range of MS risk factors and the gut microbiome. We postulate that the gut microbiome serves as the niche where different MS risk factors merge, thereby influencing the disease process.

Expression of a second ecto-5'-nucleotidase variant besides the usual protein in symptomatic phase of experimental autoimmune encephalomyelitis

Ecto-5'-nucleotidase/cluster of differentiation 73 (CD73) (eN) is a 70-kDa glycoprotein expressed in several different mammalian tissues and cell types. It is the rate-limiting enzyme of the purine catabolic pathway, which catalyzes the hydrolysis of AMP to produce adenosine with known anti-inflammatory and immunosuppressive actions. There is strong evidence for lymphocyte and endothelial cell eN having a role in experimental autoimmune encephalomyelitis (EAE), but the role of eN in cell types within the central nervous system is less clear. We have previously shown that eN activity significantly increased in the lumbar spinal cord during EAE. The present study is aimed to explore molecular pattern of the eN upregulation over the course of the disease and cell type(s) accountable for the induction. EAE was induced in Dark Agouti (DA) rats by immunization with the spinal cord tissue homogenate and adjuvant. Animals were sacrificed 8, 15, and 28 days following immunization (D8, D15, and D28), i.e., at time points which corresponded to the presymptomatic, symptomatic, and postsymptomatic phases of the disease, respectively. Significant increase in eN activity and its upregulation at the gene and the protein levels were demonstrated at D15 and less prominently at D28 in comparison to control. Additionally, reactive astrocytes abundantly present in the lumbar spinal cord parenchyma were identified as principal cell type with significantly elevated eN expression. In all experimental groups, eN was expressed as a 71-kDa protein band of uniform abundance, whereas the overexpression of eN at D15 and D28 was associated with the expression of a second 75-kDa eN variant. The possible outcome of eN upregulation during EAE as a part of protective astrocyte repertoire contributing to the resolution of the disease is discussed.

Regulatory T-cell vaccination independent of auto-antigen

To date, efforts to treat autoimmune diseases have primarily focused on the disease symptoms rather than on the cause of the disease. In large part, this is attributed to not knowing the responsible auto-antigens (auto-Ags) for driving the self-reactivity coupled with the poor success of treating autoimmune diseases using oral tolerance methods. Nonetheless, if tolerogenic approaches or methods that stimulate regulatory T (T_reg) cells can be devised, these could subdue autoimmune diseases. To forward such efforts, our approach with colonization factor antigen I (CFA/I) fimbriae is to establish bystander immunity to ultimately drive the development of auto-Ag-specific T_reg cells. Using an attenuated Salmonella vaccine expressing CFA/I fimbriae, fimbriae-specific T_reg cells were induced without compromising the vaccine's capacity to protect against travelers' diarrhea or salmonellosis. By adapting the vaccine's anti-inflammatory properties, it was found that it could also dampen experimental inflammatory diseases resembling multiple sclerosis (MS) and rheumatoid arthritis. Because of this bystander effect, disease-specific T_reg cells are eventually induced to resolve disease. Interestingly, this same vaccine could elicit the required T_reg cell subset for each disease. For MS-like disease, conventional CD25⁺ T_reg cells are stimulated, but for arthritis CD39⁺ T_reg cells are induced instead. This review article will examine the potential of treating autoimmune diseases without having previous knowledge of the auto-Ag using an innocuous antigen to stimulate T_reg cells via the production of transforming growth factor-β and interleukin-10.

The role of Staphylococcal enterotoxin A in achieving oral tolerance to myelin basic protein in adult mice

BACKGROUND

Oral tolerance is the biological process explaining the non-responsiveness of gut lymphoid tissue to intestinal content. Our study tested a new approach for the enhancement of oral tolerance to a multiple sclerosis-triggering auto-antigen-myelin basic protein, by its oral administration with the Staphylococcal enterotoxin A.

METHODS

Immune tolerance thus stimulated was assessed in adult BALB/c mice, by measuring different cytokines from the supernatant of mesenteric lymph nodes cells (IFN-γ, IL-4, IL-10, IL-17, and TGF-β), and in a SJL/E mouse model of experimental autoimmune encephalomyelitis, by evaluating the development of regulatory T cells in mesenteric lymph nodes and the clinical outcome of the intervention.

RESULTS

We obtained a significant rise in the levels of IL-10 and TGF-β compared with control and a significant decrease of IFN-γ, IL-4 (p < 0.05). Regulatory T cells were increased compared with control (p < 0.05). These results were attributable both to myelin basic protein and to Staphylococcal enterotoxin A. The clinical outcome of experimental autoimmune encephalomyelitis was influenced only by the administration of myelin basic protein.

CONCLUSION

In our experiment, Staphylococcal enterotoxin A enhanced the immune tolerance to myelin basic protein in the gut mucosa, but had no impact on the clinical evolution of experimental autoimmune encephalomyelitis.

Immunomodulatory activity of polysaccharides isolated from Clerodendrum splendens: beneficial effects in experimental autoimmune encephalomyelitis

BACKGROUND

Extracts of leaves from Clerodendrum have been used for centuries to treat a variety of medicinal problems in tropical Africa. However, little is known about the high-molecular weight active components conferring therapeutic properties to these extracts.

METHODS

Polysaccharides from the leaves of Clerodendrum splendens were extracted and fractionated by ion exchange and size-exclusion chromatography. Molecular weight determination, sugar analysis, degree of methyl esterification, and other chemical characterization of the fractions were performed. Immunomodulatory activity of the fractions was evaluated by determining their ability to induce monocyte/macrophage nitric oxide (NO), cytokine production, and mitogen-activated protein kinase (MAPK) phosphorylation. Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice, and severity of EAE was monitored in mice treated with intraperitoneal (i.p.) injections of the most active polysaccharide fraction. Lymph nodes (LN) and spleen were harvested, and levels of cytokines in supernatants from LN cells and splenocytes challenged with myelin oligodendrocyte glycoprotein peptide were determined.

RESULTS

Fractions containing type II arabinogalactan had potent immunomodulatory activity. Specifically, the high-molecular weight sub-fraction CSP-AU1 (average of 38.5 kDa) induced NO and cytokine [interleukin (IL)-1α, -1β, -6, -10, tumor necrosis factor (TNF; designated previously as TNF-α), and granulocyte macrophage-colony stimulating factor (GM-CSF)] production by human peripheral blood mononuclear cells (PBMCs) and monocyte/macrophages. CSP-AU1-induced secretion of TNF was prevented by Toll-like receptor 4 (TLR4) antagonist LPS-RS, indicating a role for TLR4 signaling. Treatment with CSP-AU1 also induced phosphorylation of a number of MAPKs in human PBMC and activated AP-1/NF-κB. In vivo treatment of mice with CSP-AU1 and CSP-NU1 resulted in increased serum IL-6, IL-10, TNF, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1α/CCL3, and MIP-1β/CCL4. CSP-AU1 treatment of mice with EAE (50 mg/kg, i.p., daily, 13 days) resulted in significantly reduced disease severity in this experimental model of multiple sclerosis. Levels of IL-13, TNF, interferon (IFN)-γ, IL-17, and GM-CSF were also significantly decreased, whereas transforming growth factor (TGF)-β was increased in LN cells from CSP-AU1-treated EAE mice.

CONCLUSIONS

Polysaccharide CSP-AU1 is a potent natural innate immunomodulator with a broad spectrum of agonist activity in vitro and immunosupressive properties after chronic administration in vivo.

Evaluation of the immunosuppressive activity of artesunate in vitro and in vivo

Artemisinin and its derivatives have been reported to have immunosuppressive activity in some laboratory studies. However, the detail of mechanism remains to be demonstrated. The objective of this study is to clarify the immunosuppressive activity of artesunate (AST), one kind of artemisinin derivatives, and to find its unexplored mode of action. In vitro, the proliferation of T lymphocytes and its cytotoxicity were measured by WST-1 and MTT assay. In vivo, the immunomodulatory effect of AST was evaluated in a mouse model of delayed type hypersensitivity reaction (DTH), which was based on a T cell-mediated immune response. The data displayed that AST had a relatively high immunosuppressive activity with low toxicity, and could inhibit T lymphocyte proliferation induced by mitogen and alloantigen. Meanwhile, topical administration of AST could suppress DTH response significantly. Moreover, AST could also increase the secretion of TFG-β, coupling with the striking enhance of NF-κB/p65 and Smad2/3 signaling. The promotion of CD4(+)CD25(+) regulatory T cells (Tregs) was shown to be a possible mechanism involved in AST-mediated regulation. Taken together, these observations exhibit the potential of developing AST as a novel safe remedy for the treatment of T cell-mediated immune disorders.