间充质干细胞对Th17/Treg平衡的影响及与IBD的关系

辅助性T细胞17（Th17）/调节性T细胞（Treg）失衡是炎症性肠病（IBD）发病的重要因素,纠正Th17/Treg细胞失衡可以减缓或抑制IBD的发生发展,成为治疗IBD的靶点。间充质干细胞具有抗炎及免疫调节功能,通过可溶性因子、细胞接触及外泌体的方式调节适应性和先天性免疫,纠正Th17/Treg失衡缓解IBD,这给IBD的治疗提供新的方向。目前,MSCs和IBD的关系研究较少,本文综述了MSCs调节Th17/Treg平衡及与IBD的关系。     

Th17-related cytokines in inflammatory bowel diseases: friends or foes?

T helper (Th)17 cells and other interleukin (IL)-17-producing cells are supposed to play critical roles in several human immune-mediated diseases, including Crohn's disease (CD) and ulcerative colitis (UC), the main forms of inflammatory bowel diseases (IBD) in man. Th17 cells infiltrate massively the inflamed intestine of IBD patients and in vitro and in vivo studies have shown that Th17-type cytokines may trigger and amplify multiple inflammatory pathways. Nonetheless, some Th17-related cytokines, such as interleukin (IL)-17A and IL-22, may target gut epithelial cells and promote the activation of counter-regulatory mechanisms. This observation together with the demonstration that Th17 cells are not stable and can be converted into either regulatory T cells or Th1 cells if stimulated by immune-suppressive (e.g. TGF-β1) or inflammatory (e.g. IL-12, IL-23) cytokines have contributed to advance our understanding of mechanisms that regulate mucosal homeostasis and inflammation in the gut.     

New insights into the pathogenesis of cutaneous autoimmune disorders

T helper 17 (Th17) cells are characterized by the secretion of IL-17, a proinflammatory cytokine. They represent a newly described T helper subpopulation that is distinct from Th1 and Th2 lineages. Because of their pleiotropic activity on fibroblasts, keratinocytes, endothelial cells, neutrophils and memory T cells, Th17 cells are thought to be crucial in mediating tissue inflammation and autoimmunity. Autoimmune diseases were classically considered as Th1-mediated disorders such as rheumatoid arthritis or mixed Th1/Th2 diseases such as inflammatory bowel diseases, systemic lupus erythematosus, bullous diseases, but new evidence suggests the deep involvement of Th17 cells in their pathogenesis that, potentially, may address a selective therapeutic approach targeting the IL23/Th17 pathway. This review summarizes the current knowledge of the pathogenic contribution of Th17 cells in select cutaneous autoimmune disorders, including lupus erythematosus, scleroderma, dermatomyositis, bullous pemphigoid and pemphigus vulgaris.     

The Ratio of Treg/Th17 Cells Correlates with the Disease Activity of Primary Immune Thrombocytopenia

Background

Primary immune thrombocytopenia (ITP) is an autoimmune heterogeneous disorder that is characterized by decreased platelet count. Regulatory T (Treg) cells and T helper type 17 (Th17) cells are two subtypes of CD4⁺ T helper (Th) cells. They play opposite roles in immune tolerance and autoimmune diseases, while they share a common differentiation pathway. The imbalance of Treg/Th17 has been demonstrated in several autoimmune diseases. In this study, we aimed to investigate the ratio of the number of Treg cells to the number of Th17 cells in ITP patients and evaluate the clinical implications of the alterations in this ratio.

Methods

Thirty adult patients with newly diagnosed ITP enrolled in this study. Twelve patients had been clinically followed up for 12 months. The percentages of CD4⁺CD25^hiFoxp3⁺ Treg cells and CD3⁺CD4⁺IL-17-producing Th17 cells in these patients and healthy controls (n = 17) were longitudinally analyzed by flow cytometry.

Results

The percentage of Treg cells in ITP patients was significantly lower than that of healthy controls, and the percentage of Th17 cells increased significantly at disease onset. The ratio of Treg/Th17 correlated with the disease activity.

Conclusion

The ratio of Treg/Th17 might be relevant to the clinical diversity of ITP patients, and this Treg/Th17 ratio might have prognostic role in ITP patients.     

CD4+CD25+Foxp3+ regulatory T cells depletion may attenuate the development of silica-induced lung fibrosis in mice

Background

Silicosis is an occupational lung disease caused by inhalation of silica dust characterized by lung inflammation and fibrosis. Previous study showed that Th1 and Th2 cytokines are involved in silicosis, but Th1/Th2 polarization during the development of silicosis is still a matter of debate. Regulatory T cells (Treg cells) represent a crucial role in modulation of immune homeostasis by regulating Th1/Th2 polarization, but their possible implication in silicosis remains to be explored.

Methodology/Principal Findings

To evaluate the implication of Treg cells in the development of silicosis, we generated the Treg-depleted mice model by administration of anti-CD25 mAbs and mice were exposed to silica by intratracheal instillation to establish experimental model of silica-induced lung fibrosis. The pathologic examinations show that the Treg-depleted mice are susceptive to severer inflammation in the early stage, with enhanced infiltration of inflammatory cells. Also, depletion of Treg cells causes a delay of the progress of silica-induced lung fibrosis in mice model. Further study of mRNA expression of cytokines reveals that depletion of Tregs leads to the increased production of Th1-cytokines and decreased production of Th2-cytokine. The Flow Cytometry and realtime PCR study show that Treg cells exert the modulation function both directly by expressing CTLA-4 at the inflammatory stage, and indirectly by secreting increasing amount of IL-10 and TGF-β during the fibrotic stage in silica-induced lung fibrosis.

Conclusion/Significance

Our study suggests that depletion of Tregs may attenuate the progress of silica-induced lung fibrosis and enhance Th1 response and decelerate Th1/Th2 balance toward a Th2 phenotype in silica-induced lung fibrosis. The regulatory function of Treg cells may depend on direct mechanism and indirect mechanism during the inflammatory stage of silicosis.     

Reduction of Acute Rejection by Bone Marrow Mesenchymal Stem Cells during Rat Small Bowel Transplantation

Background

Bone marrow mesenchymal stem cells (BMMSCs) have shown immunosuppressive activity in transplantation. This study was designed to determine whether BMMSCs could improve outcomes of small bowel transplantation in rats.

Methods

Heterotopic small bowel transplantation was performed from Brown Norway to Lewis rats, followed by infusion of BMMSCs through the superficial dorsal veins of the penis. Controls included rats infused with normal saline (allogeneic control), isogeneically transplanted rats (BN-BN) and nontransplanted animals. The animals were sacrificed after 1, 5, 7 or 10 days. Small bowel histology and apoptosis, cytokine concentrations in serum and intestinal grafts, and numbers of T regulatory (Treg) cells were assessed at each time point.

Results

Acute cellular rejection occurred soon after transplantation and became aggravated over time in the allogeneic control rats, with increase in apoptosis, inflammatory response, and T helper (Th)1/Th2 and Th17/Treg-related cytokines. BMMSCs significantly attenuated acute cellular rejection, reduced apoptosis and suppressed the concentrations of interleukin (IL)-2, IL-6, IL-17, IL-23, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ while upregulating IL-10 and transforming growth factor (TGF)-β expression and increasing Treg levels.

Conclusion

BMMSCs improve the outcomes of allogeneic small bowel transplantation by attenuating the inflammatory response and acute cellular rejection. Treatment with BMMSCs may overcome acute cellular rejection in small bowel transplantation.     

Specific microbiota direct the differentiation of IL-17-producing T-helper cells in the mucosa of the small intestine

The requirements for in vivo steady state differentiation of IL-17-producing T-helper (Th17) cells, which are potent inflammation effectors, remain obscure. We report that Th17 cell differentiation in the lamina propria (LP) of the small intestine requires specific commensal microbiota and is inhibited by treating mice with selective antibiotics. Mice from different sources had marked differences in their Th17 cell numbers and animals lacking Th17 cells acquired them after introduction of bacteria from Th17 cell-sufficient mice. Differentiation of Th17 cells correlated with the presence of cytophaga-flavobacter-bacteroidetes (CFB) bacteria in the intestine and was independent of toll-like receptor, IL-21 or IL-23 signaling, but required appropriate TGF-beta activation. Absence of Th17 cell-inducing bacteria was accompanied by increase in Foxp3+ regulatory T cells (Treg) in the LP. Our results suggest that composition of intestinal microbiota regulates the Th17:Treg balance in the LP and may thus influence intestinal immunity, tolerance, and susceptibility to inflammatory bowel diseases.     

Heme Oxygenase-1 Ameliorates Dextran Sulfate Sodium-induced Acute Murine Colitis by Regulating Th17/Treg Cell Balance

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn''s disease, is a group of autoimmune diseases characterized by nonspecific inflammation in the gastrointestinal tract. Recent investigations suggest that activation of Th17 cells and/or deficiency of regulatory T cells (Treg) is involved in the pathogenesis of IBD. Heme oxygenase (HO)-1 is a protein with a wide range of anti-inflammatory and immune regulatory function, which exerts significantly protective roles in various T cell-mediated diseases. In this study, we aim to explore the immunological regulation of HO-1 in the dextran sulfate sodium-induced model of experimental murine colitis. BALB/c mice were administered 4% dextran sulfate sodium orally; some mice were intraperitoneally pretreated with HO-1 inducer hemin or HO-1 inhibitor stannum protoporphyrin IX. The results show that hemin enhances the colonic expression of HO-1 and significantly ameliorates the symptoms of colitis with improved histological changes, accompanied by a decreased proportion of Th17 cells and increased number of Tregs in mesenteric lymph node and spleen. Moreover, induction of HO-1 down-regulates retinoic acid-related orphan receptor γt expression and IL-17A levels, while promoting Treg-related forkhead box p3 (Foxp3) expression and IL-10 levels in colon. Further study in vitro revealed that up-regulated HO-1 switched the naive T cells to Tregs when cultured under a Th17-inducing environment, which involved in IL-6R blockade. Therefore, HO-1 may exhibit anti-inflammatory activity in the murine model of acute experimental colitis via regulating the balance between Th17 and Treg cells, thus providing a possible novel therapeutic target in IBD.     

Overexpression of GATA-3 in T Cells Accelerates Dextran Sulfate Sodium-Induced Colitis

Ulcerative colitis (UC) is an inflammatory bowel disease, and its pathogenesis includes genetic, environmental, and immunological factors, such as T helper cells and their secreted cytokines. T helper cells are classified as Th1, Th2, and Th17 cells. However, it is unclear which T helper cells are important in UC. Dextran sulfate sodium (DSS)-induced colitis is a commonly used model of UC. In this study, we induced DSS colitis in Th1 dominant (T-bet transgenic (Tg)) mice, Th2 dominant (GATA-3 Tg) mice, and Th17 dominant (RORγt Tg) mice to elucidate the roles of T helper cell in DSS colitis. The results showed that GATA-3 Tg mice developed the most severe DSS colitis compared with the other groups. GATA-3 Tg mice showed a significant decreased in weight from day 1 to day 7, and an increased high score for the disease activity index compared with the other groups. Furthermore, GATA-3 Tg mice developed many ulcers in the colon, and many neutrophils and macrophages were detected on day 4 after DSS treatment. Measurement of GATA-3-induced cytokines demonstrated that IL-13 was highly expressed in the colon from DSS-induced GATA-3 Tg mice. In conclusion, GATA-3 overexpression in T-cells and IL-13 might play important roles in the development of DSS colitis.     

Reciprocity between Regulatory T Cells and Th17 Cells: Relevance to Polarized Immunity in Leprosy

T cell defect is a common feature in lepromatous or borderline lepromatous leprosy (LL/BL) patients in contrast to tuberculoid or borderline tuberculoid type (TT/BT) patients. Tuberculoid leprosy is characterized by strong Th1-type cell response with localized lesions whereas lepromatous leprosy is hallmarked by its selective Mycobacterium leprae specific T cell anergy leading to disseminated and progressive disease. FoxP3+ Regulatory T cells (Treg) which are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases also dampen proinflammatory T cells that include T helper 17 (Th17) cells. This study is aimed at evaluating the role of Treg cells in influencing other effector T cells and its relationship with the cytokine polarized state in leprosy patients. Peripheral blood mononuclear cells from of BT/TT (n = 15) and BL/LL (n = 15) patients were stimulated with M. leprae antigen (WCL) in presence of golgi transport inhibitor monensin for FACS based intracellular cytokine estimation. The frequency of Treg cells showed >5-fold increase in BL/LL in comparison to BT/TT and healthy contacts. These cells produced suppressive cytokine, IL-10 in BL/LL as opposed to BT/TT (p = 0.0200) indicating their suppressive function. The frequency of Th17 cells (CD4, CD45RO, IL-17) was, however, higher in BT/TT. Significant negative correlation (r = -0.68, P = 0.03) was also found between IL-10 of Treg cells and IL-17+ T cells in BL/LL. Blocking IL-10/TGF-β restored the IL-17+ T cells in BL/LL patients. Simultaneously, presence of Th17 related cytokines (TGF-β, IL-6, IL-17 and IL-23) decreased the number of FoxP3+ Treg cells concomitantly increasing IL-17 producing CD4+ cells in lepromatous leprosy. Higher frequency of Programmed Death-1/PD-1+ Treg cells and its ligand, PDL-1 in antigen presenting cells (APCs) was found in BL/LL patients. Inhibition of this pathway led to rescue of IFN-γ and IL-17 producing T cells. Results indicate that Treg cells are largely responsible for the kind of immunosuppression observed in BL/LL patients. This study also proves that Treg cells are profoundly affected by the cytokine milieu and this property may be utilized for benefit of the host.     

Change of Th17 Lymphocytes and Treg/Th17 in Typical and Atypical Optic Neuritis

Background

Typical and atypical optic neuritis (ON) are two clinical types of autoimmune inflammatory diseases of the optic nerve that causes acute vision loss, and are difficult to distinguish in their early stages. The disturbance in the balance of Th17 and Treg lymphocytes is thought to play an essential role in these autoimmune inflammatory diseases.

Objectives

To detect the clinical relevance of Th17 and Treg in peripheral blood and the ratio of Treg/Th17 in patients with typical and atypical ON. To determine whether analysis of Th17 and Treg lymphocytes will provides insights into the different disease phenotypes of typical and atypical ON.

Methods

We studied a consecutive series of patients aged 14–70 years who presented to our neurological department with typical ON (n = 30) or atypical ON (n = 33) within 4 weeks of their acute attacks. Routine clinical tests and ophthalmological examination were performed in all patients. Blood samples were collected from untreated patients and from gender- and age-matched healthy controls (n = 30). The proportion of peripheral blood Th17 cells and Treg cells was determined by flow cytometry.

Results

Patients with atypical ON had a higher proportion of Th17 cells than patients with typical ON (3.61±1.56 vs 2.55±1.74, P<0.01) or controls (1.45±0.86, P<0.01). The proportion of Th17 cells in patients with typical ON was also markedly higher than in controls (P<0.01). The mean percentage of Treg cells in atypical ON (6.31±2.11) and typical ON (6.80±2.00) were significantly lower when compared to controls (8.29±2.32, both P<0.01). No significant difference in Treg frequency was observed between typical ON and atypical ON (p>0.05).

Conclusions

The frequency of Th17 cells is higher in atypical ON than typical ON, and patients with atypical ON have a greater imbalance of pro-inflammatory and regulatory cells than patients with typical ON when compared with controls. These changes are indicative of distinct pathological mechanisms and may provide useful information to distinguish typical and atypical ON.     

AKT isoforms modulate Th1‐like Treg generation and function in human autoimmune disease

Foxp3⁺ regulatory T cells (Tregs) exhibit plasticity, which dictates their function. Secretion of the inflammatory cytokine IFNγ, together with the acquisition of a T helper 1 (Th1)‐like effector phenotype as observed in cancer, infection, and autoimmune diseases, is associated with loss of Treg suppressor function through an unknown mechanism. Here, we describe the signaling events driving the generation of human Th1‐Tregs. Using a genome‐wide gene expression approach and pathway analysis, we identify the PI3K/AKT/Foxo1/3 signaling cascade as the major pathway involved in IFNγ secretion by human Tregs. Furthermore, we describe the opposing roles of AKT isoforms in Th1‐Treg generation ex vivo. Finally, we employ multiple sclerosis as an in vivo model with increased but functionally defective Th1‐Tregs. We show that the PI3K/AKT/Foxo1/3 pathway is activated in ex vivo‐isolated Tregs from untreated relapsing–remitting MS patients and that blockade of the pathway inhibits IFNγ secretion and restores the immune suppressive function of Tregs. These data define a fundamental pathway regulating the function of human Tregs and suggest a novel treatment paradigm for autoimmune diseases.     

The Crosstalk between IL-22 Signaling and miR-197 in Human Keratinocytes

The interaction between the immune system and epithelial cells is tightly regulated. Aberrations of this balance may result in inflammatory diseases such as psoriasis, inflammatory bowel disease and rheumatoid arthritis. IL-22 is produced by Th17, Th22 and Th1 cells. Putative targets for IL-22 are cells in the skin, kidney, digestive and respiratory systems. The highest expression of IL-22 receptor is found in the skin. IL-22 plays an important role in the pathogenesis of T cell-mediated inflammatory diseases such as psoriasis, inflammatory bowel disease and rheumatoid arthritis. Recently, we found that miR-197 is down regulated in psoriatic lesions. In the present work we show that miR-197 over expression inhibits keratinocytes proliferation induced by IL-22 and keratinocytes migration. In addition, we found that IL-22 activates miR-197 expression through the binding of phosphorylated STAT3 to sequences in the putative promoter of miR-197. Finally we found that IL-22 receptor subunit IL22RA1 is a direct target of miR-197. Hence, we identified a novel feedback loop controlling IL-22 signaling, in which IL-22 induces miR-197, which in turn, negatively regulates IL-22 receptor and attenuates the biological outcome of such signaling. Regulation of this pathway may be important in inflammatory skin disorders such a psoriasis and in wound healing.     

Zinc deficiency drives Th17 polarization and promotes loss of Treg cell function

A high number of illnesses and disorders are connected to zinc deficiency. Equally, T cell polarization and a balance between different T helper (Th) cell subsets are essential. Therefore, in this study, the influence of zinc deficiency on T cell polarization and on respective signaling pathways was investigated. We uncovered a significantly increased number of regulatory T cells (Treg) and Th17 cells in expanded T cells during zinc deficiency after 3 days of combined treatment with IL-2 and TGF-β1 (Treg) or IL-6 and TGF-β1 (Th17). No difference in Th1 and Th2 cell polarization between zinc-deficient and zinc-adequate status was prominent. On the molecular level, Smad signaling was significantly enhanced by stimulation with TGF-β1/IL-6 during zinc deficiency compared to adequate zinc condition. This represents an explanation for the elevated Th17 cell numbers associated with autoimmune disease especially during zinc deficiency. Moreover, Treg cell numbers are increased during zinc deficiency as well. However, those cells might be nonfunctional since a lower expression of miR-146a was uncovered compared to normal zinc concentrations. In summary, an adequate zinc homeostasis is fundamental to slow down or probably stop the progression of autoimmune diseases and infections. Therefore, supplementing zinc might be a therapeutic approach to dampen autoimmune diseases connected to Th17 cells.