Immunopathology of inflammatory bowel disease

Inflammatory bowel disease(IBD)results from a complex series of interactions between susceptibility genes,the environment,and the immune system.The host microbiome,as well as viruses and fungi,play important roles in the development of IBD either by causing inflammation directly or indirectly through an altered immune system.New technologies have allowed researchers to be able to quantify the various components of the microbiome,which will allow for future developments in the etiology of IBD.Various components of the mucosal immune system are implicated in the pathogenesis of IBD and include intestinal epithelial cells,innate lymphoid cells,cells of the innate(macrophages/monocytes,neutrophils,and dendritic cells)and adaptive(T-cells and B-cells)immune system,and their secreted mediators(cytokines and chemokines).Either a mucosal susceptibility or defect in sampling of gut luminal antigen,possibly through the process of autophagy,leads to activation of innate immune response that may be mediated by enhanced toll-like receptor activity.The antigen presenting cells then mediate the differentiation of na?ve T-cells into effector T helper(Th)cells,including Th1,Th2,and Th17,which alter gut homeostasis and lead to IBD.In this review,the effects of these components in the immunopathogenesis of IBD will be discussed.     

Th17/Treg失衡与炎症性肠病的关系

炎症性肠病(inflammatory bowel disease.IBD)的病因和发病机制尚未完全明确,肠道黏膜免疫系统异常反应所导致的炎症过程在发病中起重要作用.辅助性T细胞17(T helper 17 cells,Th17)可介导慢性炎症和自身免疫性疾病的发生,调节性T细胞(regulatory T cell,Treg)有抑制自身免疫的功能,二者存在相互转化的关系.有研究表明Th17/Treg转化平衡是维持肠道免疫稳态的重要因素,这可能是导致人类IBD的原因之一.最近研究表明TGF-β,IL-6和维甲酸(retinoic acid,RA)可能是调控二者平衡关系的重要因素.肠道菌群(intestinal flora)与IBD的发生发展关系密切,益生菌(probiotics)对IBD的治疗作用成为研究的热点.深化对Th17/Treg转化调控关系的研究是当前重要的研究课题.     

Unveiling the biological role of sphingosine-1-phosphate receptor modulators in inflammatory bowel diseases

Inflammatory bowel disease(IBD) is chronic inflammation of the gastrointestinal tract that has a high epidemiological prevalence worldwide. The increasing disease burden worldwide, lack of response to current biologic therapeutics, and treatment-related immunogenicity have led to major concerns regarding the clinical management of IBD patients and treatment efficacy. Understanding disease pathogenesis and disease-related molecular mechanisms is the most important goal in developing new and effec...     

Potential role of Th17 cells in the pathogenesis of inflammatory bowel disease

The etiopathology of inflammatory bowel disease (IBD) remains elusive. Accumulating evidence suggests that the abnormality of innate and adaptive immunity responses plays an important role in intestinal inflammation. IBD including Crohn's disease (CD) and ulcerative colitis (UC) is a chronic inflammatory disease of the gastrointestinal tract, which is implicated in an inappropriate and overactive mucosal immune response to luminal flora. Traditionally, CD is regarded as a Th1mediated inflammatory disorder while UC is regarded as a Th2like disease. Recently, Th17 cells were identified as a new subset of T helper cells unrelated to Th1 or Th2 cells, and several cytokines [e.g. interleukin (IL)-21, IL-23] are involved in regulating their activation and differentiation. They not only play an important role in host defense against extracellular pathogens, but are also associated with the development of autoimmunity and inflammatory response such as IBD. The identification of Th17 cells helps us to explain some of the anomalies seen in the Th1/Th2 axis and has broadened our understanding of the immunopathological effects of Th17 cells in the development of IBD.     

Promises and paradoxes of regulatory T cells in inflammatory bowel disease

Since their discovery two decades ago,CD4+CD25+Foxp3+ regulatory T cells(Tregs) have become the subject of intense investigation by immunologists. Unlike other T cells,which promote an immune response,Tregs actively inhibit inflammation when activated by their cognate antigen,thus raising hope that these cells could be engineered into a highly targeted,antigenspecific,immunosuppressant therapy. Although Tregs represent less than 10% of circulating CD4+T cells,they have been shown to play an essential role in preventing or limiting inflammation in a variety of animal models and human diseases. In particular,spontaneous intestinal inflammation has been shown to occur in the absence of Tregs,suggesting that there may be a Treg defect central to the pathogenesis of human inflammatory bowel disease(IBD). However,over the past decade,multiple groups have reported no qualitative or quantitative deficits in Tregs from the intestines and blood of IBD patients to explain why these cells fail to regulate inflammation in Crohn's disease and ulcerative colitis. In this review,we will discuss the history of Tregs,what is known about them in IBD,and what progress and obstacles have been seen with efforts to employ them for therapeutic benefit.     

Contribution of the IL-17/IL-23 axis to the pathogenesis of inflammatory bowel disease

Inflammatory bowel diseases(IBDs) are chronic disorders of modern society, requiring management strategies aimed at prolonging an active life and establishing the exact etiology and pathogenesis.These idiopathic diseases have environmental, genetic,immunologic, inflammatory, and oxidative stress components. On the one hand, recent advances have shown that abnormal immune reactions against the microorganisms of the intestinal flora are responsible for the inflammation in genetically susceptible individuals. On the other hand, in addition to T helper cell-type(Th) 1 and Th2 immune responses,other subsets of T cells, namely regulatory T cells and Th17 maintained by IL-23 are likely to develop IBD. IL-23 acts on innate immune system members and also facilitates the expansion and maintenance of Th17 cells. The IL-17/IL-23 axis is relevant in IBD pathogenesis both in human and experimental studies. Novel biomarkers of IBD could be calprotectin,microRNAs, and serum proinflammatory cytokines.An efficient strategy for IBD therapy is represented by the combination of IL-17 A and IL-17 F in acute IL-17 A knockout TNBS-induced colitis, and also definite decrease of the inflammatory process in IL-17 F knockout, DSS-induced colitis have been observed.Studying the correlation between innate and adaptive immune systems, we hope to obtain a focused reviewin order to facilitate future approaches aimed at elucidating the immunological mechanisms that control gut inflammation.     

调节性T细胞在炎症性肠病中的研究进展

炎症性肠病(IBD)是一种非特异性肠道炎症性疾病,其发病与自身免疫功能紊乱有关.Th1/Th2失衡是导致IBD的重要因素之一.然而,Th1/Th2理论并不能充分阐明IBD的发病机制.近几年来,越来越多的研究显示,调节性T细胞在炎症性肠病的发生发展中起重要的作用.本文就近年来调节性T细胞在炎症性肠病中作用的研究进展作一综述.     

New insights into the cellular immunology of the intestine in relation to the pathophysiology of inflammatory bowel diseases

The authors review advances about altered immunological cellular mechanisms in inflammatory bowel diseases (IBD). The innate immune response might play a role in the inductive phase : epithelial barrier defect, production of inflammatory cytokines and defective neutrophil function. Dendritic cells have a pivotal role, since they sense the nature of the micro-organisms in the intestine in order to drive either adaptive immune responses through IL-12 or IL-4 and co-stimulatory molecules, or immunotolerance through regulatory T cells (Tr). T helper(Th)1 cytokines (IFNgamma, TNF-alpha, IL-12) are secreted in excess in Crohn's disease (CD) whereas in ulcerative colitis an atypical Th2 immune response (IL-4, TGFbeta) has been reported. However, activation of Th can only lead to effective immune response if co-stimulatory molecules expressed on activated T cells bind to their specific ligands on the antigen-presenting-cells, mesenchymal and endothe-, lial cells. This binding is necessary to generate an effective immune response, to enhance expression of adhesion molecules and T cell recruitment, promoting chronic inflammation in IBD. A defective function of Tr might contribute to excessive T cell response. Innate CD4 + CD25 + Tr derived from the thymus represent 5-10% of T cells in peripheral lymphoid organs. Acquired peripheral Tr downregulate the immune response through IL-10 and TGF-beta production. In IBD effector T cells might downregulate the development of Tr cells in the thymus. Another defective mechanism in CD is T cell resistance to apoptosis, leading to inappropriate immune homeostasis and accumulation of T cells in the tissues. New therapeutic agents have been proposed for correcting deficiencies of innate immunity or reducing excessive immune responses, with promising results confirmed by randomized controlled trials.     

Immunological basis of inflammatory bowel disease: role of the microcirculation.

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the intestine and/or colon of unknown etiology in which patients suffer from severe diarrhea, rectal bleeding, abdominal pain, fever, and weight loss. Active episodes of IBD are characterized by vasodilation, venocongestion, edema, infiltration of large numbers of inflammatory cells, and erosions and ulcerations of the bowel. It is becoming increasingly apparent that chronic gut inflammation may result from a dysregulated immune response toward components of the normal intestinal flora, resulting in a sustained overproduction of proinflammatory cytokines and mediators. Many of these Th1 and macrophage-derived cytokines and lipid metabolites are known to activate microvascular endothelial cells, thereby promoting leukocyte recruitment into the intestinal interstitium. This review discusses the basic immune mechanisms involved in the regulation of inflammatory responses in the gut and describes how a breakdown in this protective response initiates chronic gut inflammation.     

树突状细胞与1型糖尿病的关系

1型糖尿病是一种T淋巴细胞介导的器官特异性自身免疫性疾病,表现为胰岛β细胞的选择性破坏.树突状细胞(DCs)作为体内最重要的专职性抗原递呈细胞,在1型糖尿病的发病机制中具有极其重要的作用.DCs具有功能上的可塑性,不同类型DCs、不同成熟状态的DCs以及DCs所处微环境的不同,都将诱导其产生不同的功能状态.通过调节DCs的不同功能状态促进中枢或外周免疫耐受、扩展胰岛特异性调节性T细胞(CD4~+ CD25~+ Treg cell)、以及介导辅助性T(Th)细胞发生Th1/Tk2细胞的免疫偏离,可诱导免疫耐受,预防1型糖尿病的发生.     

γδT细胞在肺部铜绿假单胞菌感染的研究现状

γδT细胞是T细胞的一个亚群,存在Th1／Th2免疫模式,主要分布在皮肤、肠道、呼吸道及泌尿生殖道的黏膜和皮下组织,在感染性疾病的免疫应答中发挥着第一道防线的作用。铜绿假单胞菌是临床常见的致病菌,感染所诱发的免疫反应是以Th2型为主,伴有明显的第Ⅲ型超敏反应所导致的器官损害。铜绿假单胞菌感染时γδT细胞明显升高,γδT细胞可能通过分泌不同的细胞因子影响Th1／Th2平衡,进而影响铜绿假单胞菌感染性疾病的发生、发展。     

Th17细胞及IL-23在炎症性肠病中的研究进展

炎症性肠病(IBD)是一种病因和发病机制尚不清楚的发生在胃肠道的慢性非特异性炎症性疾病。大量证据表明先天性和获得性免疫系统的异常均对该疾病起着关键性作用。传统观点认为炎症性肠病与Th1细胞和Th2细胞所介导的免疫应答有关;但最新研究指出,体内Th17细胞以及白细胞介素IL-23的存在,与炎症性肠病的发生息息相关。本文对炎症性肠病中Th17细胞及IL-23的研究进展作一综述。     

Predominant T helper 1 cells in patients with idiopathic portal hypertension

BACKGROUND: The pathologic mechanism of idiopathic portal hypertension (IPH) is unknown. Because cytokines and the balance of T helper (h) 1 and Th2 CD4+ T cells have been reported to be important for regulating the immune response, in the present study we investigated the role of cytokines and the distribution of cytokine-producing cells in IPH patients. METHODS: Serum levels of tumor necrosis factor (TNF)-alpha, soluble TNF receptor-I, -II, interferon (IFN)-gamma and interleukin (IL)-4 were measured in IPH patients, fatty liver patients, chronic hepatitis patients and control subjects. The percentages of Th0, Th1 and Th2 CD4+ T cells were examined in peripheral and spleen lymphocytes in IPH patients by intracellular staining. RESULTS: Serum levels of TNF-alpha, soluble TNF receptor-I, interferon-gamma and IL-4 of IPH patients were not increased in comparison with control subjects. Only the mean value of soluble TNF receptor-II was significantly higher than that of control subjects and fatty liver patients. The ratios of Th1 and Th2 in both peripheral and spleen lymphocytes of IPH patients were significantly increased compared with the ratios found in peripheral lymphocytes of control subjects. The increase in the ratios was due to a decrease in the percentage of Th2 CD4+ T cells. CONCLUSIONS: These results suggest that the imbalance of Th1 and Th2 CD4+ T cells and TNF may be associated with the pathogenesis of IPH.     

辅助性T细胞的研究概况及进展

CD4~ Th细胞是机体重要的免疫调节细胞,根据其产生细胞因子的不同分为Th1和Th2亚型,分别参与调节细胞免疫和体液免疫.Th1和Th2可相互调节,影响免疫应答的格局.他们来自共同的前体细胞Th0,在不同的细胞因子、抗原等因素的影响下,可发生Th1与Th2的转换.在生理条件下,机体Th1/Th2细胞的免疫功能处于动态平衡,一旦这种平衡发生偏离,机体就会趋向疾病状态.     

Liver-infiltrating and circulating CD4+ T cells in chronic hepatitis C: immunodominant epitopes,HLA-restriction and functional significance

Abstract: The aim was to assess the specificity and functional significance of liver-infiltrating and peripheral blood T cells in chronic hepatitis C. Peripheral blood mononuclear cells hepatitis C virus from 50 of 58 (86.2%) patients with chronic hepatitis C virus infection and 6 of 28 (21.4%) controls showed a proliferative T cell response to at least one of 16 synthetic peptides covering highly conserved regions of the core, envelope (El) and non-structural regions (NS4) of hepatitis C virus. However, six immunodominant peptides were exclusively recognized by the proliferating blood mononuclear cells from 46 patients with chronic hepatitis C virus infection (79.3%). Fine specificity and HLA-restriction were studied with 15 peptide-specific CD4+ T cell lines and 23 T cell clones isolated from liver tissue and peripheral blood of 12 patients with chronic hepatitis C. It was demonstrated that the peptide-specific response of CD4+ T cells was restricted to the presence of autologous accessory cells and HLA-DR and -DP molecules. Eight peptide-specific T cell lines and five T cell clones derived from liver tissue and peripheral blood, released interferon-γ (200–6600 pg/ml) and tumor necrosis factor-α (100–400 pg/ml) and no or little interleukin-4 (<140 pg/ml) after peptide-specific or mitogeneic stimulation, thus resembling a Th1-like cytokine profile. Patients with active liver disease showed significantly higher proliferative responses to hepatitis C virus core peptides than asymptomatic hepatitis C virus carriers or complete responders to interferon therapy. In conclusion, class II-restricted CD4+ T cell responses to some immunodominant epitopes within the hepatitis core region correlated with disease activity in chronic hepatitis C virus infection. Functionally, liver-infiltrating and peripheral blood T cells released Th1-like cytokines in response to the specific stimulus. Thus, it can be suggested that CD4+ T cells can mediate the pathogenesis of chronic hepatitis C virus induced liver disease.     

Vitamin D improves inflammatory bowel disease outcomes:Basic science and clinical review

Vitamin D deficiency is commonly diagnosed among patients with inflammatory bowel disease(IBD).Patients with IBD are at risk of low bone density and increased fractures due to low vitamin D levels,long standing disease,and frequent steroid exposures;as a result,it is well established that vitamin D supplementation in this population is important.There is increasing support for the role of vitamin D in strengthening the innate immune system by acting as an immunomodulator and reducing inflammation in experimental and human IBD.The active form of vitamin D,1,25(OH)D3,acts on T cells to promote T helper(Th)2/regulatory T responses over Th1/Th17 responses;suppresses dendritic cell inflammatory activity;induces antibacterial activity;and regulates cytokine production in favor of an antiinflammatory response.Murine and human IBD studies support a therapeutic role of vitamin D in IBD.Risk factors for vitamin D deficiency in this population include decreased sunlight exposure,disease duration,smoking,and genetics.Vitamin D normalization is associated with reduced risk of relapse,reduced risk of IBD-related surgeries,and improvement in quality of life.Vitamin D is an inexpensive supplement which has been shown to improve IBD outcomes.However,further research is required to determine optimal serum vitamin D levels which will achieve beneficial immune effects,and stronger evidence is needed to support the role of vitamin D in inducing disease response and remission,as well as maintaining this improvement in patients’disease states.     

调节性T细胞与支气管哮喘的研究进展

支气管哮喘(简称哮喘)是一种慢性气道炎症性疾病,尤以机体Th2型免疫反应为主要表现,而近年来的大量研究表明调节性T细胞具有抑制Th2型反应的功能.通过对哮喘患者体内的调节性T细胞进行干预,来达到对哮喘的治疗和预防作用,已成为且前哮喘领域研究的热点.