Gene expression study of two widely used pig intestinal epithelial cell lines: IPEC-J2 and IPI-2I

The intestinal epithelial cells (IEC) play an important role in the immune system of swine, protecting against infectious and non-infectious environmental insults. The IEC participate in the innate immune response of the intestine through different mechanisms such as barrier function, mucus secretion, antibacterial peptide synthesis and participation in the cytokine/chemokine networks.Most of the current knowledge of intestinal cell functions has come from studies conducted on cell cultures generated from human cancers or from classical animal models. However, because the molecular and cellular elements of the immune system have been selected over evolutionary time in response to the species-specific environment, models of immune function based on mouse and human need to be applied cautiously in pig. Few models of swine small intestine epithelium exist and these are poorly characterised. In the present study we characterised the basal expression of epithelial and immune-related genes of two pig small intestine cell lines, IPEC-J2 and IPI-2I, under different culture conditions. These data represent essential background information for future studies on pig-intestinal pathogen interactions.     

Advances in Modulation of Intestinal Innate Defense Responses by Probiotic Bacteria

Probiotics are a kind of living microorganism which can be administered in feed and confer numerous health benefits to animals. Probiotics play a key role in maintaining the microbial balance of gastrointestinal, immunomodulation and pathogen defense, specific probiotics show certain degree of potential to reinforce the integrity of intestinal epithelium and regulate some immune components. The mechanism of probiotic action is an area of interest. Among all possible routes of modulation by probiotics of intestinal mediated defense responses, modulations of intestinal barrier function, innate and adaptive mucosal immune responses as well as signaling pathways are considered to play an important role in the intestinal defense responses against pathogenic bacteria. This review summarizes how probiotic bacteria interact with goblet cell-derived mucins, trefoil factors (TFFs),defensins, Toll-like receptors (TLRs), secretory immunoglobulin A (sIgA), heat shock proteins (HSPs) and P-glycoproteins (P-gp) in the gut to regulate the intestinal innate defense responses,which is regarded as the scientific basis for the future detailed study of benefits of probiotics towards the health of intestine and also dietary intervention against intestinal exposure to pathogens.     

益生菌对肠道先天防御反应调节作用的研究进展

益生菌是可添加在饲料中对动物健康产生很多益处的活微生物,其在维持胃肠道微生物平衡、免疫调节和病原体防御中起关键作用,某些特定的益生菌菌株对加强肠上皮的完整性和调节一些免疫组分也显示出一定程度的潜力。有关益生菌的作用机制是当前研究的热点,其中,在益生菌调节肠道介导的防御反应的所有可能途径中,肠屏障功能、先天和适应性黏膜免疫反应及信号传导途径被认为在针对病原菌的肠防御反应中起重要作用。作者主要针对益生菌如何与肠道内的杯状细胞黏蛋白、三叶因子（trefoil factors,tffs）、防御素、Toll样受体（Toll-like receptors,TLRs）、分泌型免疫球蛋白A（secretory immunoglobulin A,sIgA）、热休克蛋白（heat shock proteins,HSPs）和P-糖蛋白（P-glycoprotein,P-gp）相互作用而起到调节肠道先天防御反应的作用进行了概述,以期为今后研究益生菌对肠道健康及对感染病原体的肠道如何起到有益作用奠定基础。     

肥大细胞在动物肠道黏膜免疫屏障中的作用

肠道黏膜屏障包括机械屏障和免疫屏障等,后者主要由肠黏膜吸收上皮细胞和肠道相关淋巴组织构成。肠道黏膜免疫细胞包括淋巴细胞、杯状细胞、肥大细胞等。其中肥大细胞是天然免疫的效应细胞之一,其不仅在天然免疫中发挥重要作用,且能通过所分泌的细胞因子参与获得性免疫。笔者综述了肥大细胞的生物学特性及其在肠道免疫屏障中的作用。     

The effects of mycotoxins, fungal food contaminants, on the intestinal epithelial cell-derived innate immune response

Mycotoxins are structurally diverse fungal metabolites that can contaminate a variety of dietary components consumed by animals and humans. It is considered that 25% of the world crop production is contaminated by mycotoxins. The clinical toxicological syndromes caused by ingestion of moderate to high amounts of mycotoxins and their effect on the immune system have been well characterized. However, no particular attention has been focused on the effects of mycotoxins on the local intestinal immune response. Because of their location, intestinal epithelial cells (IECs) could be exposed to high doses of mycotoxins. As a component of the innate local immune response, intestinal epithelial cells have developed a variety of mechanisms which act to reduce the risk of infection by microorganisms or intoxication by toxic compounds. This review summarises the innate immune response developed by intestinal epithelial cells and reports the literature concerning the effects of mycotoxins on them. Particularly, the effects of mycotoxins on the maintenance of a physical barrier by epithelial cells will be discussed together with their effect on extrinsic protective components of the innate intestinal immunity: mucus secretion, antimicrobial peptide generation, IgA and pro-inflammatory cytokine release.     

甘露寡糖对保育猪的营养与保健作用

大量研究表明,甘露寡糖(MOS)通过积极影响断奶仔猪的肠道微生物菌群和肠道形态结构,加速由于断奶饥饿应激或采食固体饲料中抗原受损伤的肠黏膜上皮的修复,有助于保持仔猪断奶后肠道的完整性和消化吸收功能。在免疫反应方面,MOS通过促进抗原提呈增强断奶仔猪的抗病性,从而增强从先天性免疫应答向适应性免疫应答的转变。     

乳酸杆菌益生作用机制的研究进展

乳酸杆菌作为益生菌广泛用于人和动物。本文综述了乳酸杆菌改善宿主健康的机制。乳酸杆菌可通过产生抗菌物质如乳酸、过氧化氢、细菌素,或者通过竞争营养或肠道黏附位点来抑制致病菌;通过诱导黏附素的分泌或阻止细胞凋亡而增强肠道的屏障功能,从而保护肠道。文章重点讨论了乳酸杆菌表面成分（表面蛋白、脂磷壁酸和肽聚糖）与肠道受体（Ｃ型凝集素受体、Ｔｏｌｌ样受体和 Ｎｏｄ样受体）,阐述了他们结合后启动免疫调节信号,调控肠道免疫功能以发挥改善健康作用的机制。     

Characterization of turkey inducible nitric oxide synthase and identification of its expression in the intestinal epithelium following astrovirus infection

The inducible nitric oxide synthase (iNOS) enzyme has long been recognized as a key mediator of innate immune responses to infectious diseases across the phyla. Its role in killing or inactivating bacterial, parasitic, and viral pathogens has been documented in numerous host systems. iNOS, and its innate immune mediator NO has also been described to have negative consequence on host tissues as well; therefore understanding the pathogenesis of any infectious agent which induces iNOS expression requires a better understanding of the role iNOS and NO play in that disease. Previous studies in our laboratory and others have demonstrated evidence for increased levels of iNOS and activity of its innate immune mediator NO in the intestine of turkeys infected with astrovirus. To begin to characterize the role iNOS plays in the innate immune response to astrovirus infection, we identified, characterized, developed tkiNOS specific reagents, and demonstrated that the intestinal epithelial cells induce expression of iNOS following astrovirus infection. These data are the first to our knowledge to describe the tkiNOS gene, and demonstrate that astrovirus infection induces intestinal epithelial cells to express iNOS, suggesting these cells play a key role in the antiviral response to enteric infections.     

中性粒细胞胞外诱捕网与病原体的相互作用及其机制

中性粒细胞作为机体天然免疫系统的重要组成部分，发挥至关重要的防御病原体感染的作用。中性粒细胞发挥防御作用的机制之一是通过释放中性粒细胞胞外诱捕网（neutrophil extracellular traps，NETs）捕获并消灭病原体。然而有些病原体已进化出逃避NETs的机制，从而对机体造成持续损伤。此外，NETs的异常状态也会对机体造成一些损伤。近年来，NETs已成为中性粒细胞功能研究的热点，受到了国内外学者的广泛关注。有学者在禽的异嗜性粒细胞中也发现了类似NETs功能的网状结构，并将其命名为异嗜性粒细胞胞外诱捕网（heterophil extracellular traps，HETs）。作者主要对NETs抵御病原体入侵和病原体逃避NETs的机制并引起宿主致病等过程进行综述。     

病原微生物荚膜多糖的生物学功能

荚膜多糖（capsular polysaccharide，CPS）是一种广泛存在于细菌、支原体、部分真菌等菌体表面的碳水化合物。同时，荚膜多糖有助于菌体抵抗干燥和低温等不利环境，并通过在菌体表面形成物理屏障阻碍宿主补体的杀伤与吞噬作用。在长期多种应激-压力环境下，病原菌已进化出多种免疫逃避机制并促进宿主感染；在非病原微生物中，荚膜多糖可正向调节宿主免疫作用，并拮抗机体免疫因子，保护宿主免受病原菌引起的炎症性疾病。本文将结合本团队的相关研究工作，对荚膜多糖的结构、合成调控机制、生物学功能、免疫逃避机制和致病机制，特别是荚膜多糖正向调节宿主免疫系统及其应用潜力等方面作一综述，为病原菌致病机制的研究和疫病的有效防控提供参考依据。     

单胃动物肠道菌群与宿主肠道免疫系统的互作关系及可能机制

单胃动物的肠道中存在着庞大而复杂的菌群,它们与宿主肠道免疫系统协同进化。肠道细菌及其代谢产物在维持肠道稳态方面发挥着重要的作用。正常的肠道菌群能促进免疫系统发育,参与维持宿主免疫功能,协同拮抗病原菌的增殖和入侵。反过来,宿主肠道免疫系统对肠道菌群又有制约和调控作用,如对正常共生菌表现为免疫耐受,对病原菌表现为免疫排斥。一旦这种动态平衡被破坏,就会导致疾病的发生。本文综述了单胃动物肠道菌群与宿主肠道免疫系统的相互关系,并基于现有的研究结果,对其可能的互作机制做了较为系统的总结。     

断奶对仔猪肠道屏障的影响及营养调控

在集约化养殖中,3~4周龄早期断奶是仔猪生命周期中一个非常紧张的时期,此时仔猪胃肠道还未发育成熟。肠道屏障由上皮、免疫和肠神经系统组成,这些系统控制上皮屏障的完整性以及肠道功能,包括肠腔营养物质、水和电解质的运输。早期断奶导致肠道通透性增加,出现胃肠功能紊乱的情况,可能对猪只一生产生长期的影响。因此,仔猪断奶饲粮需要正确水平的营养素、营养源和高质量的添加剂,鼓励仔猪快速进食,减轻或消除断奶应激综合症,降低死亡率和发病率。养猪就是养"肠道",合理使用功能性氨基酸、植物化学物质和有机酸等添加剂,能够修复由于断奶应激综合症导致的肠道屏障功能障碍。     

Research Advance on Intestinal Microbial-epithelial Cell Barrier Interactions

Intestinal epithelial cells (IECs) are the first line of defense against pathogenic microorganisms of animal organism, which are important component of mucosal mechanical barrier, immune barrier and chemical barrier, they have absorption and barrier double function. In the intestine, there are many kinds of microorganisms. According to its relationship with the host, it is divided into three types of commensal bacteria, conditional pathogenic bacteria and pathogenic bacteria, it plays an important role in the construction of intestinal barrier. Firstly, IECs identify the intestinal microbes by direct or indirect ways, and distinguish their own and non-self, it is immune tolerance to their own substances (such as, commensal bacteria), and produce specific immune response to non-self-substances (pathogenic bacteria). Both of IECs and intestinal commensal bacteria together against pathogens maintain intestinal health. When the pathogenic microorganisms invade the intestine, IECs defense pathogenic microorganisms mainly through extracellular secretions and cell surface mucus layer, and the former largely include mucin, antibacterial molecular and antimicrobial immunoglobulin. The intestinal symbiotic bacteria can resist the pathogenic microorganisms and maintain the normal intestinal mucosal barrier function through the competitive identification sites, the secretion of antimicrobial substances, the increase of mucus secretion, the induction of IECs renewal, proliferation and repair. In the process of resisting invasion of gut microbes, pathogenic microorganisms through their own movement, secretion of toxins and enzymes to destroy the intestinal epithelial barrier, and directly contact with IECs to damage them. So the interaction between IECs and intestinal bacteria maintain the intestinal homeostasis. In this paper, a review is made of the IECs and intestinal microbial structure and functional adaptations, and hope to elaborate the mechanism of intestinal microbial-epithelial cell barrier interaction.     

肠道微生物-上皮细胞屏障互作的研究进展

肠道上皮细胞（intestinal epithelial cells,IECs）是动物机体抵御病原微生物的第一道防线,是黏膜机械屏障、免疫屏障和化学屏障的重要组成部分,具有吸收和屏障双层功能。肠道中微生物数量庞大、种类繁多,根据其与宿主的关系,主要分为共生菌、条件致病菌和病原菌3类,在肠道屏障的构建中发挥重要作用。IECs首先通过直接或间接方式对肠道微生物进行识别,区别自身与非自身,对自身物质（即共生菌）免疫耐受,对非自身物质（即病原菌）产生特异性免疫反应。IECs与肠道共生菌共同抵御肠道病原微生物,维持肠道健康,病原微生物侵入肠道,IECs主要通过胞外分泌物和细胞表面黏液层双重屏障发挥作用,其中胞外分泌物主要包括黏蛋白、抗菌分子和抗微生物免疫球蛋白。肠道共生菌可以通过竞争识别位点,分泌抗菌物质,增加黏液分泌,诱导IECs更新、增殖和修复等方式抵御病原微生物,维护正常的肠黏膜屏障功能。在IECs抵御肠道病原微生物入侵过程中,病原微生物通过自身运动、分泌毒素和酶等破坏肠上皮屏障,直接接触IECs,对其进行损伤。因此IECs和肠道菌群间相互作用,共同维持肠道内环境稳态。作者就IECs和肠道微生物结构、功能的适应性变化作一综述,以期阐述肠道微生物-上皮细胞屏障互作的机制。     

Interactions between commensal bacteria and the gut-associated immune system of the chicken

The chicken gut-associated lymphoid tissue is made up of a number of tissues and cells that are responsible for generating mucosal immune responses and maintaining intestinal homeostasis. The normal chicken microbiota also contributes to this via the ability to activate both innate defense mechanisms and adaptive immune responses. If left uncontrolled, immune activation in response to the normal microbiota would pose a risk of excessive inflammation and intestinal damage. Therefore, it is important that immune responses to the normal microbiota be under strict regulatory control. Through studies of mammals, it has been established that the mucosal immune system has specialized regulatory and anti-inflammatory mechanisms for eliminating or tolerating the normal microbiota. The mechanisms that exist in the chicken to control host responses to the normal microbiota, although assumed to be similar to that of mammals, have not yet been fully described. This review summarizes what is currently known about the host response to the intestinal microbiota, particularly in the chicken.     

Toll-like receptor expression in feline lymphoid tissues

Toll-like receptors (TLRs) are germline-encoded pattern recognition receptors (PRRs) that activate the innate immune system. While it is clear that TLRs are important in the immune response against pathogens, they may also be exploited by some pathogens. Our objective is to determine whether feline immunodeficiency virus (FIV) infection affects TLR expression or function thereby resulting in innate immune dysfunction. To this end, we cloned partial sequences for feline TLRs 1--3, 5--8, and developed real-time PCR assays to quantify feline TLRs 1--9. TLR expression was quantified in normal cat lymphoid tissues, purified lymphocyte subsets, and FIV-infected cell lines. Different expression patterns of TLRs were found in spleen, mesenteric lymph node, retropharyngeal lymph node, thymus, intestinal intraepithelial lymphocytes, and lamina propria lymphocytes. B lymphocytes, CD4+ T cells, and CD8+ T cells all expressed TLRs 2--5, 7--9; however, the relative levels of expression varied among lymphocyte phenotypes. Infection of cell lines with FIV resulted in altered TLR expression levels that differed depending on cell type. These results demonstrate that tissue distribution of TLRs is associated with the immunological role of a particular tissue, that lymphocytes may also express these 'innate immune' receptors, and that FIV infection can alter TLR expression.     

Perspectives in mucosal immunity: a ruminant model

All mammalian species have developed specialized defence mechanisms at the interface between mucosal surfaces and the environment and this system operates independently of the systemic immune system. Attachment of organisms to the mucosal epithelium is a primary prerequisite for infection and is an important virulence determinant for pathogens of these sites. The mucosal immune defences are thus characterized by production of IgA antibodies, the principal mode of action of which is to inhibit the adherence of pathogens to the mucosal epithelium. This introduction to the symposium on mucosal immunity will attempt to underline the role of local immunity in the intestine in providing local defence at that site, in addition to providing cellular molecular effectors for other mucosal sites.     

Porcine intestinal epithelial responses to Campylobacter infection

Campylobacter infection is estimated to cause diarrhoea in 1% of the population of developed countries every year, but our understanding of this disease has been hampered by a lack of a suitable animal model. Colostrum-deprived piglets have been suggested as models since they produce similar clinical signs to humans when infected but little information currently exists regarding the response of this species to Campylobacter at cellular and molecular level. This study shows that intestinal epithelial cells from both species respond in a similar manner to Campylobacter infection regarding invasion, induction of innate immune response and effect on barrier function.     

肠道菌群对动物肠黏膜免疫的调控作用

动物肠道共生着数量庞大、结构复杂的菌群,而肠壁内存在着为数众多、功能强大的黏膜淋巴细胞。肠道菌群具有促进肠黏膜免疫系统生长与发育和调控肠黏膜屏障与免疫功能的双重作用。本文主要从动物肠道菌群的定植与特性、肠黏膜免疫细胞的功能以及肠道菌群对肠黏膜屏障与免疫功能的调控作用进行综述。     

Immunobiotic lactic acid bacteria beneficially regulate immune response triggered by poly(I:C) in porcine intestinal epithelial cells

ABSTRACT: This study analyzed the functional expression of TLR3 in various gastrointestinal tissues from adult swine and shows that TLR3 is expressed preferentially in intestinal epithelial cells (IEC), CD172a+CD11R1high and CD4+ cells from ileal Peyer's patches. We characterized the inflammatory immune response triggered by TLR3 activation in a clonal porcine intestinal epitheliocyte cell line (PIE cells) and in PIE-immune cell co-cultures, and demonstrated that these systems are valuable tools to study in vitro the immune response triggered by TLR3 on IEC and the interaction between IEC and immune cells. In addition, we selected an immunobiotic lactic acid bacteria strain, Lactobacillus casei MEP221106, able to beneficially regulate the anti-viral immune response triggered by poly(I:C) stimulation in PIE cells. Moreover, we deepened our understanding of the possible mechanisms of immunobiotic action by demonstrating that L. casei MEP221106 modulates the interaction between IEC and immune cells during the generation of a TLR3-mediated immune response.