中性粒细胞细胞外诱捕网的研究进展

中性粒细胞是机体先天性免疫系统中的重要组成成分,是外周血中数量最多的免疫细胞,在非特异性免疫中至关重要,是构成机体内抵御微生物入侵的第一道防线。近年来,人们发现中性粒细胞除了经典的通过胞吞作用吞噬病原微生物、释放嗜天青颗粒及产生并分泌抑菌杀菌物质外,还具有抵抗微生物入侵的新机制——中性粒细胞细胞外诱捕网(neutrophil extracellular traps,NETs)。该机制主要通过活性氧和肽酰基精氨酸脱亚氨酶4等影响因子刺激中性粒细胞形成以DNA为骨架的网状结构,内含有多种蛋白酶,能非特异性捕获杀伤病原体,还能在机体某些疾病的产生和发展中起到协同作用。作者就NETs的形成、影响因素及与病原、疾病的相互关系作一概述,为进一步研究中性粒细胞的功能提供依据。     

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。     

高乙酰乙酸诱导中性粒细胞胞外诱捕网的形成

中性粒细胞胞外诱捕网(NETs)是几年前才发现的一种重要的先天免疫防御机制,目前NETs的发生机制尚不清楚,但是当缺乏有效抗衡调节时,它又能损伤组织、引发自身免疫等疾病。本试验为了研究作为酮病奶牛高酮血症的主要成分之一的乙酰乙酸(ACAC)对NETs表达量的影响,体外添加不同浓度ACAC处理中性粒细胞,运用免疫荧光技术和激光共聚焦显微成像定性评价NETs的生成;采用PicoGreen~dsDNA染料定量检测细胞上清游离DNA和Western blot反映NETs生成量。结果显示,高ACAC组产生NETs的量显著高于对照组组(P0.05),表明高ACAC可以体外成功诱导中性粒细胞产生NETs。     

沉默中性粒细胞Orai1影响NETs内ROS的表达

旨在研究不同时间与浓度的佛波肉豆蔻酸乙酸酯(PMA)对奶牛中性粒细胞(PMN)形成中性粒细胞胞外诱捕网(NETs)效果,筛选出PMA刺激时间与浓度,通过流式细胞术检测NETs状态下沉默中性粒细胞Orai1,检测钙离子与ROS水平。尾静脉肝素抗凝采集血液分离中性粒细胞,分别在不同时间与不同浓度PMA刺激下,根据激光共聚焦镜下观察NETs的形态状态。结果显示,在PMA在100 nm状态下刺激3 h时NETs形成状态效果最好。在沉默Orai1状态下,通过流式细胞检测结果显示,NETs内钙离子与ROS水平极显著降低。     

禽异嗜性粒细胞与机体免疫研究进展

禽异嗜性粒细胞是存在于禽类血液中的一种主要的颗粒性白细胞,类似于哺乳动物的中性粒细胞,是禽类抵御外界微生物病原体入侵的一道重要防线,也是机体非特异性免疫系统中的重要成员和主要调节者。近年来,对于该细胞在机体急性炎症反应和吞噬杀伤作用中的研究已经深入到了基因和蛋白水平,为从禽类异嗜性粒细胞方面入手治疗禽类疾病,提供了理论依据和研究方向。论文从异嗜性粒细胞与中性粒细胞在形态结构,急性炎症反应和吞噬杀伤病原体作用中的区别,以及近年来该细胞的其他研究热点等方面综述了禽类异嗜性粒细胞的研究进展。     

哺乳动物防御素

自然界中充满各种各样的微生物，要想在这个世界中生存，必须具有完备的防御体系。哺乳动物的免疫系统就是逐渐分化而来的这样一个防御体系，它包括特异性免疫和非特异性免疫。非特异性免疫对各种入侵机体内的微生物在最初反应中起关键作用，其中哺乳动物防御素(defensins)是哺乳动物非特异性免疫的主要成分。在哺乳动物多形核粒细胞和上皮组织内存在一类富含半胱氨酸的抗微生物肽，称为防御素。     

家禽免疫的概念与分类

现代免疫学的概念是：机体识别和清除非自身的大分子物质,从而保持机体内外环境平衡的生理学反应。免疫的基本功能包括：抵抗微生物与寄生虫的感染,清除衰老死亡的细胞,保持机体自身稳定,严密监视肿瘤细胞的出现,一旦出现就能立即识别,并调动免疫系统在其尚未发展之前将其消灭。1先天性免疫先天性免疫是指家禽生来就已具有的对某种病原微生物及其毒素的抵抗能力。1.1防御屏障皮肤、粘膜、腱鞘、肌膜、浆膜等的屏障作用以及血脑屏障、胎盘屏障等等。1.2吞噬作用嗜中性粒细胞、     

白细胞抗细菌机制研究取得重要突破

<正>嗜中性粒细胞是哺乳动物外周血中非常重要的一类白细胞,它是最早对入侵病原微生物做出免疫反应的固有免疫细胞。在感染的早期,嗜中性粒细胞能够通过吞噬细菌或者直接释放自身的水解酶达到清除细菌的目的。同时,嗜中性粒细胞还能够对细菌做出免疫应答,产生促炎症因子如TNF、IL-6等,招募     

中性粒细胞在实验感染E.coli性乳腺炎母牛的全身和局部…

病原微生物侵入乳腺后，乳腺白细胞是天然防卫屏障的主要成员，本文评述母牛患急性埃希氏大肠杆菌性乳腺炎过程中，中性粒细胞的功能和作用。     

金黄色葡萄球菌CHIPS研究进展

趋化抑制蛋白(Chemotaxis Inhibitory Protein of Staphylococcus aureus,CHIPS)是由金黄色葡萄球菌体外的一种蛋白质。在感染早期,它能特异性地与中性粒细胞和单核细胞上的C5a受体(C5aR)和fLMP受体(FPR)结合,从而阻止中性粒细胞和单细胞与C5a和fMLP的结合作用,导致对病原吞噬作用的延迟。人们可以利用CHIPS对C5a-C5aR的阻止作用来研制治疗由C5a诱发的炎症性疾病的药物。将CHIPS作为免疫原来预防和治疗由金黄色葡萄球菌引起的疾病也将成为新的研究课题。     

Neutrophil extracellular traps in sheep mastitis

Neutrophil extracellular traps (NETs) are structures composed of DNA, histones, and antimicrobial proteins that are released extracellularly by neutrophils and other immune cells as a means for trapping and killing invading pathogens. Here, we describe NET formation in milk and in mammary alveoli of mastitic sheep, and provide a dataset of proteins found in association to these structures. Nucleic acid staining, immunomicroscopy and fluorescent in-situ hybridization of mastitic mammary tissue from sheep infected with Streptococcus uberis demonstrated the presence of extranuclear DNA colocalizing with antimicrobial proteins, histones, and bacteria. Then, proteomic analysis by LTQ-Orbitrap Velos mass spectrometry provided detailed information on protein abundance changes occurring in milk upon infection. As a result, 1095 unique proteins were identified, of which 287 being significantly more abundant in mastitic milk. Upon protein ontology classification, the most represented localization classes for upregulated proteins were the cytoplasmic granule, the nucleus, and the mitochondrion, while function classes were mostly related to immune defence and inflammation pathways. All known NET markers were massively increased, including histones, granule proteases, and antimicrobial proteins. Of note was the detection of protein arginine deiminases (PAD3 and PAD4). These enzymes are responsible for citrullination, the post-translational modification that is known to trigger NET formation by inducing chromatin decondensation and extracellular release of NETs. As a further observation, citrullinated residues were detected by tandem mass spectrometry in histones of samples from mastitic animals. In conclusion, this work provides novel microscopic and proteomic information on NETs formed in vivo in the mammary gland, and reports the most complete database of proteins increased in milk upon bacterial mastitis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13567-015-0196-x) contains supplementary material, which is available to authorized users.     

Essential role of neutrophils but not mammary alveolar macrophages in a murine model of acute Escherichia coli mastitis

Mastitis, the inflammation of the mammary gland, is an important disease affecting dairy animals worldwide. The disease is caused by mammary pathogenic bacteria and Escherichia coli are frequently implicated. Virulence factors of mammary pathogenic E. coli are only partially known and intramammary challenge with LPS elicits neutrophil recruitment in experimental bovine and murine mastitis models. We have previously shown that neutrophil recruitment in LPS-induced murine mastitis is strictly dependent on mammary alveolar macrophages. However, the relative role of alveolar macrophages and blood neutrophils in E. coli mastitis is not well defined. To this end, we selectively depleted mammary alveolar macrophages or blood neutrophils before intramammary challenge with E. coli strain P4 (ECP4). Mice depleted of alveolar macrophages prior to intramammary challenge recruited neutrophils normally and restricted bacterial growth and interstitial invasion. Importantly however, upon depletion of alveolar macrophages, ECP4 invaded the mammary alveolar epithelial cells and formed intracellular bacterial communities. In contrast, neutrophil depletion prior to intramammary infection with ECP4 was associated with unrestricted bacterial growth, tissue damage, severe sepsis and mortality. This study suggests that neutrophils but not alveolar macrophages provide essential antimicrobial defense against mammary pathogenic E. coli. Furthermore, we show here similar invasion after depletion of alveolar macrophages as in our previous studies showing that LPS/TLR4 signaling on alveolar macrophages abrogates ECP4 invasion of the mammary epithelium. Interestingly, similar ECP4 invasion and formation of intracellular communities were also observed following intramammary infection of either iNOS gene-deficient or IL-1 receptor type 1 gene-deficient mice.     

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。     

A review of the interaction of Bacillus anthracis with cells of the innate immune response

Bacillus anthracis spores cause natural infections and can be used as biological weapons.The innate immune response is the first line of defence against invading pathogens and is likely to play a central role in this acute infection.To date the immune evasion mechanisms of B. anthracis are not well understood. Infection by inhalation with B. anthracis, the etiological agent of anthrax, is almost always lethal, yet cutaneous infections usually remain localized and resolve spontaneously in the majority of cases. Neutrophils are typically recruited to cutaneous but seldom to other forms of anthrax infections, raising the possibility that neutrophils kill B. anthracis. This is an overview of the interaction of B. anthracis with innate immune cells which also focuses on recent data on the role neutrophils play in anthrax pathogenesis. These data suggest that the timely recruitment of neutrophils can control the cutaneous and possibly other forms of B. anthracis infections and that the neutrophil granule proteins, a-defensins, play an important role in the potent anti-B. anthracis activity of neutrophils.     

Impact of nutrition on the innate immune response to infection in poultry

Viral and bacterial diseases remain a threat to the poultry industry and countermeasures to prevent and control them are needed due to production losses. With the continued threat of exotic and emerging diseases and concern over the use of antibiotics in animal production, there is a serious and urgent need to find safe and practical alternatives to prevent or control pathogens. Identification of new tools for the design of new immunological interventions or therapeutic antimicrobials to reduce microbial pathogens in poultry is now required more than ever. Immunological interventions to reduce microbial pathogens in poultry would be of great value to the poultry industry and to the consumer. We have been advocating boosting immunity and encouraging the host to utilize its innate immune system to control and clear infections. Our research has addressed the use of innate immune mechanisms and components to develop new immune modulators (prophylactic and therapeutic) and the characterization and production of antimicrobial peptides as potential immune modulators in poultry. Dietary bioactive food components that interact with the immune response have considerable potential to reduce susceptibility to infectious diseases. With this premise, this paper asks and answers a series of pertinent questions on the utilization of avian immunity for increasing resistance to a variety of potential pathogens problematic in today's commercial poultry industry. Using experimental data to provide answers to these questions, we hope to stimulate a dialog between avian immunologists and nutritionists that results in coordinating and integrating their expertise into specific practical solutions that will benefit the industry and improve the well-being of commercial poultry.     

Neutrophil extracellular trap formation by bovine neutrophils is not inhibited by milk

Neutrophils are the first line of defense in a mammary gland infection. However, the process of neutrophil transmigration across a membrane and ingestion of fat and/or casein when incubated in milk have been shown to inhibit bacterial phagocytosis and oxidative burst functions. Recently, a killing mechanism has been described whereby stimulated neutrophils release nuclear and granule material in fibrous webs that physically trap and kill bacteria. We demonstrate that these neutrophil extracellular traps are also produced by bovine blood neutrophils stimulated with PMA/ionomycin. Importantly, neutrophil extracellular traps can be formed when neutrophils have been incubated for up to 6h in milk prior to stimulation. This contrasts milk's rapid inhibition of bacterial phagocytosis and oxidative burst functions in the neutrophil. Furthermore, stimulation of neutrophils with bacteria common to mammary gland infections leads to neutrophil extracellular traps being formed in milk. Some bacteria tested stimulated enhanced formation of neutrophil extracellular traps in milk compared to culture media. Therefore, being unaffected by incubation in milk may indicate an important role for neutrophil extracellular traps in defense against mastitis.     

Veterinary ocular microbiome: Lessons learned beyond the culture

Ocular pathogens cause many painful and vision‐threatening diseases such as infectious keratitis, uveitis, and endophthalmitis. While virulent pathogens and pathobionts play important roles in disease pathogenesis, the scientific community has long assumed disruption of the ocular surface occurs prior to microbial colonization and subsequent infection. While nonpathogenic bacteria are often detected in corneal and conjunctival cultures from healthy eyes, cultures also frequently fail to yield growth of common ocular pathogens or nonpathogenic bacteria. This prompts the following question: Is the ocular surface populated by a stable microbial population that cannot be detected using standard culture techniques? The study of the microbiome has recently become a widespread focus in physician and veterinary medicine. Research suggests a pivotal symbiotic relationship with these microbes to maintain healthy host tissues, and when altered is associated with various disease states (“dysbiosis”). The microbiota that lives within and on mammalian bodies have long been known to influence health and susceptibility to infection. However, limitations of traditional culture methods have resulted in an incomplete understanding of what many now call the “forgotten organ,” that is, the microbiome. With the introduction of high‐throughput sequencing, physician ophthalmology has recognized an ocular surface with much more diverse microbial communities than suspected based on traditional culture. This article reviews the salient features of the ocular surface microbiome and highlights important future applications following the advent of molecular techniques for microbial identification, including characterizing ocular surface microbiomes in our veterinary species and their potential role in management of infectious and inflammatory ocular diseases.