呼吸道分泌型IgA研究进展1

人体粘膜是病原微生物等抗原性异物入侵机体的主要途径,机体近50%的淋巴组织分布于粘膜系统.粘膜相关淋巴组织(Mucosal-associated lymphoid tissue,MALT)是发生局部特异性免疫应答的主要部位,MALT中的B细胞多为产生分泌型IgA(Secretory IgA,SIgA)的B细胞,这是因为表达IgA的B细胞可趋向定居于派氏集合淋巴结和固有层淋巴组织,B细胞在粘膜局部受抗原刺激后产生的大量SIgA经粘膜上皮分泌至粘膜表面,成为粘膜局部抵抗病原微生物感染的主要机制.当前对SIgA在呼吸道粘膜相关淋巴组织中的作用方式研究日趋深入和广泛,本文就呼吸道SIgA生成调节、参与病理生理过程及相关呼吸道疾病等方面研究进展综述如下.     

丙型肝炎患者血清SIgA含量的变化及意义

血清SIgA主要是肠道相关的淋巴组织来源的多聚体IgA(PolymericIgA, P-IgA),用抗SIgA特有成分—分泌成分(Secretory Conponent, SC)抗血清可从血清总IgA中测出SIgA。由于SIgA存在肠肝循环,肝、胆疾病时含量可显著升高。本文报道丙型肝炎患者血清中SIgA含量。 对象和方法 一、对象: (一)正常人:35人。均为我院门诊体检合格的正常人,均无心、肝、肺、肾等重要脏器疾患、肝肾功能试验正常。 (二)病人组:31人。均为本院门诊和住院患者,全部病例均符合临床诊断,抗HCV阳性。 二、方法:放射免疫分析法。试剂盒IgA由上海放射免疫分析技术研究所提供,SIgA由中国同位素公司北方免疫试剂研究所提供,按各自说明书进行操作。受检者空腹抽血后,分离血清后冰冻保存     

唾液SIgA与小儿呼吸道感染关系的探讨

<正> 近年来有关呼吸道粘膜局部分泌型IgA(SIgA)的报道较多,但结论尚不一致,为了探讨SIgA与小儿呼吸道感染性疾病及其血清IgA间的关系,特对58例呼吸道感染患儿进行了唾液SIg人及血清IgA的测定,现报告如下。     

支气管哮喘患者血清分泌型免疫球蛋白A含量变化

血清分泌型免疫球蛋白A(SIgA)主要是肠道及支气管等相关淋巴组织来源的多聚体IgA(Polymeric IgA,pIgA),用抗SIgA特有成分—分泌成分(Secretory Component,SC)抗血清可从血清总IgA中测出SIgA。为探讨血清SIgA含量测定作为支气管哮喘(简称哮喘)的免疫学论断指标,我们观察了100例该病患者其含量变化,并分别与血清IgA、血清总IgE、血清IgG、唾液SIgA含量进行相关分析,初步探讨其临床意义。     

过敏性支气管哮喘患者粘膜SIgA免疫功能的研究

在进一步明确疾病诊断和改进测定方法的基础上,本文从外分泌液中SIgA和外周血淋巴细胞培养上清液中IgA含量测定两个方面对过敏性哮喘患者的粘膜SIgA免疫功能进行了研究。过敏性哮喘病人唾液SIgA粘膜局部分泌率与鼻分泌液中SIgA含量均较正常人显著增高(p=0.028,0.021),表明过敏性哮喘患者可能呈粘膜SIgA免疫高反应状态。其外周血淋巴细胞培养上清液中IgA含量与唾液、鼻分泌液中SIgA含量无明显相关性,提示过敏性哮喘病人粘膜IgA分泌细胞的功能异常可能与细胞免疫调节障碍有关。     

缺铁性贫血患者血清SIgA含量观察

血清SIgA主要是肠道相关的淋巴组织来源的多聚体IgA(Polymeric IgA,PIgA),用抗SIgA特有成份——分泌成份(Secretory Component,SC)抗血清可从血清总IgA中测出SIgA。有关缺铁性贫血患者血清中SIgA含量测定结果国内实属少见报到,为此,     

嗜酸乳杆菌合生元对抗生素相关腹泻大鼠肠黏膜屏障的保护作用研究

目的:探讨嗜酸乳杆菌(L.acidophilus)和低聚异麦芽糖(IMO)组成的合生元对抗生素相关腹泻(Antibiotic-associated diarrhea, AAD)大鼠肠黏膜生物屏障、免疫屏障和机械屏障的保护作用.方法:以盐酸林可霉素复制AAD模型,治疗组采用不同剂量的合生元灌胃,分别在实验第6d、第9d、第13d进行肠道菌群分析、肠黏膜SIgA检测(放射免疫分析)和肠黏膜形态学观察.结果:AAD大鼠肠道菌群失调,肠黏膜组织中SIgA水平下降;给予合生元后能调节肠道菌群失调、促进肠黏膜SIgA水平的分泌,促进小肠绒毛的修复,尤以中高剂量组较为明显.结论:嗜酸乳杆菌和低聚异麦芽糖组成的合生元配方对AAD大鼠肠黏膜生物屏障、免疫屏障和机械屏障均具有较好的保护作用.     

人轮状病毒抗原非复制型重组腺病毒黏膜免疫效果的研究

目的：对人轮状病毒抗原非复制型重组腺病毒诱导黏膜免疫的效果进行初步评价。方法：用表达轮状病毒VP7、VP6基因的3株重组腺病毒rvAdG1VP7(G)、rvAdG1VF7和rvAdVP6，分别通过灌胃和滴鼻两种途径对BALB／C小鼠进行2次免疫后，对肺灌洗液和肺、肠粘膜组织匀浆液中轮状病毒特异性的分泌型IgA(secretory IgA，SIgA)和local-IgG进行检测。结果：对肺灌洗液中特异性SIgA进行检测，发现滴鼻组的免疫学效果明显优于灌胃组。对肺、肠组织匀浆液中特异性IgA的分析表明，灌胃途径刺激异位粘膜组织产生免疫应答的能力较弱。对rvAdVP6滴鼻组小鼠肺灌洗液(1：20)特异性local-IgG和SIgA的阳转率进行比较，发现特异性local-IgG的应答水平明显高于特异性SIgA。结论：重组腺病毒可有效诱导针对轮状病毒的黏膜免疫。此研究为轮状病毒基因工程疫苗的免疫方案、免疫途径及免疫保护作用等的进一步研究莫定了基础。     

乙肝患者血清SIgA含量的变化及意义

血清SIgA主要是肠道相关淋巴组织来源的多聚体IeA(Po1ymeeric IgA,P-IgA),用抗SIgA特有成分—分泌成分(Secretory Conponent,SC)抗血清可从血清总IgA中测出SIgA。由于SIgA存在肠肝循环,肝胆疾病时含量显著地增高。为此,我们测定了104名乙肝患者血清SIgA含量,并就临床意义作初步探讨,现报道如下。 对象和方法 一、对象: (一)正常人:35人(男25,女10)。均为我院门诊体检合格的健康人,均无心、肝、肺、肾等重要脏器疾患,肝、肾功能试验正常,年龄20～31岁。 (二)乙肝患者:104人。按1984年(南宁)全国     

中药预防流感作用与黏膜免疫相关性研究

目的:研究中药预防流感的作用与黏膜免疫相关性。方法:(1)不同预防方药预防给药对正常小鼠黏膜免疫的影响:将BALB/c小鼠随机分6组。设空白对照组(生理盐水)、利巴韦林组、银翘散制剂、玉屏风散制剂、冰香散滴鼻组、冰香散雾化组。给药第12天,杀剖小鼠,空白对照组称体重和肺重测定肺指数。各组均采血分离血清,收集鼻咽冲洗液、支气管肺泡灌洗液、肠道冲洗液进行ELISA法检测IgA含量。(2)不同预防方药预防给药对流感病毒感染小鼠黏膜免疫的影响:将BALB/c小鼠随机分6组,设病毒对照组及药物试验组(同前)。试验药物在滴鼻感染15 LD50流感病毒液感染攻击前提前给药一周,攻击后继续给药5天。共给药12天,每天一次给药。感染后5天,杀剖小鼠,称体重和肺重测定肺指数。采血分离血清,收集鼻咽冲洗液、支气管肺泡灌洗液、肠道冲洗液进行ELISA法检测IgA含量。结果:(1)不同预防方药预防给药对正常小鼠黏膜免疫的影响:连续给予正常小鼠12天试验药物,利巴韦林、银翘散制剂、玉屏风散制剂、冰香散对流感病毒鼠肺指数均有显著的改善作用,肺指数抑制率达到25.46%～41.61%。与空白对照组相比,银翘散制剂口服与冰香散雾化给药血清IgA水平显著提高;冰香散滴鼻给药鼻咽部sIgA水平显著提高;利巴韦林组给药支气管-肺泡sIgA水平下降;银翘散、玉屏风散、冰香散给药肠道sIgA水平有一定的提升作用,其中玉屏风散制剂作用明显。(2)不同预防方药预防给药对流感病毒感染小鼠黏膜免疫的影响:病毒感染小鼠攻击前预先连续给药7天,病毒感染第5天,与病毒对照组相比,利巴韦林给药血清IgA水平显著降低、冰香散雾化给药血清IgA水平显著提高;冰香散滴鼻给药能使鼻咽部sIgA水平显著提高;利巴韦林组给药支气管-肺泡sIgA水平下降,玉屏风散与冰香散雾化给药支气管-肺泡sIgA水平显著提高;玉屏风散制剂与冰香散雾化给药肠道sIgA水平显著提高。结论:利巴韦林长期预防给药(100 mg/kg)对黏膜免疫IgA分泌有一定抑制作用,不宜推荐作为流感病毒的预防性长期用药。中药预防流感的三种给药方式:口服、烟薰、芳香佩戴等均可作用于呼吸道或消化道黏膜,激发局部黏膜免疫产生分泌型IgA,从而起到预防和治疗的效果。中药预防流感的作用与黏膜免疫有一定的相关性。     

Secretory component: a new role in secretory IgA-mediated immune exclusion in vivo

Secretory immunoglobulin (Ig) A (SIgA) is essential in protecting mucosal surfaces. It is composed of at least two monomeric IgA molecules, covalently linked through the J chain, and secretory component (SC). We show here that a dimeric/polymeric IgA (IgA(d/p)) is more efficient when bound to SC in protecting mice against bacterial infection of the respiratory tract. We demonstrate that SC ensures, through its carbohydrate residues, the appropriate tissue localization of SIgA by anchoring the antibody to mucus lining the epithelial surface. This in turn impacts the localization and the subsequent clearance of bacteria. Thus, SC is directly involved in the SIgA function in vivo. Therefore, binding of IgA(d/p) to SC during the course of SIgA-mediated mucosal response constitutes a crucial step in achieving efficient protection of the epithelial barrier by immune exclusion.     

Significance of different J chain profiles in human tissues: generation of IgA and IgM with binding site for secretory component is related to the J chain expressing capacity of the total local immunocyte population, including IgG and IgD producing cells, and depends on the clinical state of the tissue

Most IgA producing cells in normal intestinal and nasal mucosa synthesize dimers or larger polymers as evidenced by 90% cytoplasmic affinity for secretory component (SC) in vitro and almost 100% J chain positivity. The comparable median figures for normal exocrine glands (salivary, lacrimal, lactating mammary) were 84% and 92%, respectively. Conversely, IgA immunocytes in the subepithelial areas of palatine tonsils and in other extraglandular tissues, such as inflamed gingiva and intestinal submucosa, showed only 16-28% SC binding capacity and 18-51% J chain positivity. Similarly decreasing J chain expression, from glandular to extraglandular sites, was revealed not only for IgM immunocytes but also for those producing IgD or IgG, particularly the latter. This observation indicated more extensive overall clonal maturation in tissues without glandular elements since J chain expression seems to be a feature of relatively early memory B cells. The results were supported by studies in patients with selective IgA deficiency. Inflammatory disease caused significantly reduced SC binding capacity of IgA cells, both in intestinal mucosa and tonsils; this change was paralleled by decreased J chain expression, not only for mucosal and tonsillar IgA cells but also for mucosal IgG cells, suggesting local appearance of more mature clones. The resulting change to production of monomeric IgA may adversely affect secretory immunity and thus contribute to perpetuation of chronic inflammatory disease.     

Role of J chain in secretory immunoglobulin formation

The joining (J) chain is a small polypeptide, expressed by mucosal and glandular plasma cells, which regulates polymer formation of immunoglobulin (Ig)A and IgM. J-chain incorporation into polymeric IgA (pIgA, mainly dimers) and pentameric IgM endows these antibodies with several salient features. First, a high valency of antigen-binding sites, which makes them suitable for agglutinating bacteria and viruses; little or no complement-activating potential, which allows them to operate in a noninflammatory fashion; and, most importantly, only J-chain-containing polymers show high affinity for the polymeric Ig receptor (pIgR), also known as transmembrane secretory component (SC). This epithelial glycoprotein mediates active external transfer of pIgA and pentameric IgM to exocrine secretions. Thus, secretory IgA (SIgA) and SIgM, as well as free SC, are generated by endoproteolytic cleavage of the pIgR extracellular domain. The secretory antibodies form the 'first line' of defence against pathogens and noxious substances that favour the mucosae as their portal of entry. The J chain is involved in creating the binding site for pIgR/SC in the Ig polymers, not only by determining the polymeric quaternary structure but apparently also by interacting directly with the receptor protein. Therefore, both the J chain and the pIgR/SC are key proteins in secretory immunity.     

Effect of Hyperoxia on Pulmonary SIgA and Its Components, IgA and SC

Purpose

Oxygen therapy (hyperoxia) is essential for the treatment of some neonatal critical care conditions. The lung is the primary target for the changes induced by hyperoxia. Secretory immunoglobulin A (SIgA), IgA and secretory component (SC) reflect the local immunity in the respiratory tract induced by hyperoxia.

Methods

The enzyme-linked immunosorbent assay, immunohistochemistry staining, Western blot and Real-time PCR were used to detect the levels of cytokines, IgA and SIgA in bronchoalveolar lavage as well as IgA and SC/pIgR in pulmonary tissue.

Results

The levels of IgA and SIgA in BAL fluid were gradually increased following neonatal rat development. Compared with air-inhaling group, in the hyperoxia group IgA, SIgA and other cytokines except IL-1 in BAL fluid were significantly elevated on the 3rd, 5th and 7th days, but on the 10th day TNF-α, SIgA and IgA rapidly decreased. In the hyperoxia group, both the protein expression of SC/pIgR and the mRNA expression of SC/pIgR were remarkably increased on the 3rd, 5th and 7th days, but were significantly decreased on the 10th day, respectively. Conclusion: The large amount of SIgA, IgA and SC in the early period of hyperoxia might protect the lungs of the neonatal rats against acute pulmonary injury, however, in the late period of hyperoxia, the abruptly drop of SIgA and its component might lead to pulmonary immunity abnormality. In hyperoxia, the increased expression of cytokines might contribute to the expression of IgA and SC.     

Oral tonsils: an immunoperoxidase study

Tissue morphometry and the distribution of cells containing immunoglobulin (Ig), J chain and secretory component (SC) were studied in eight oral tonsils. Quantitative immunohistochemistry revealed that IgG-containing cells predominated in all lymphoid compartments (follicles, extrafollicular areas and reticular epithelium) and that the IgG:IgA:IgM class ratios of the overall tonsillar immunocyte population were 13:8:2. Cells containing IgD and IgE were rare. IgG immunocytes showed no significant localisation within a given lymphoid compartment, whereas IgA cells were found predominantly in extrafollicular areas, especially adjacent to surface epithelium, and IgM cells were in follicles. J chain was present within IgM and some IgA cells. Tonsillar crypt and surface epithelium was negative for SC, suggesting that these structures are not directly involved in local mucosal immunity.     

Recombinant expression of polymeric IgA: incorporation of J chain and secretory component of human origin.

Mucosal J (joining) chain-expressing IgA immunocytes produce dimeric IgA that is actively transported by the epithelial polymeric Ig receptor (pIgR) to exocrine secretions. Release of secretory IgA (SIgA) occurs by cleavage of the covalently linked pIgR ectodomain, also known as bound secretory component. We have identified the human J-chain cDNA sequence through database screening, and isolated it from B cells for recombinant expression. Co-expression of this cDNA with an alpha heavy chain and a lambda light chain in Chinese hamster ovary (CHO) cells resulted in a mixture of recombinant monomeric and dimeric IgA in culture supernatants. This dimeric IgA was transported by the pIgR-mediated mechanism in vitro. Furthermore, expression of the human pIgR ectodomain together with the dimeric IgA, resulted in production of complete SIgA by the CHO cells. These results demonstrated that co-expression of the necessary polypeptide components allows a single mammalian cell to produce SIgA. Development of production systems for human antigen-specific recombinant SIgA may be important for applications in passive mucosal vaccination.     

Location of secretory component on the Fc edge of dimeric IgA1 reveals insight into the role of secretory IgA1 in mucosal immunity

Secretory immunoglobulin A (SIgA) is the most prevalent antibody in the human body and a first line of defense in mucosal immunity. We located secretory component (SC) relative to dimeric IgA1 (dIgA1) within the SIgA1 structure using the constrained modeling of solution scattering and analytical ultracentrifugation data. The extended solution structure of dIgA1 is largely preserved within SIgA1. From conformational searches of SC locations, the best-fit SC models within SIgA1 show that SC is extended along the outermost convex edge of the Fc dimer in dIgA1. The topology of our SIgA1 structure reveals that it is able to bind to one FcαRI receptor molecule. SC binding to the Fc dimer confers protection to SIgA1 by the masking of proteolytically susceptible surface sites from bacterial proteases in the harsh environment of the mucosa. The models support a “zipper-like” unfolding of SC upon dIgA1 in the formation and transportation of SIgA1 into the mucosa.     

Role of secretory antibodies in the defence against infections

Adaptive immunity mediated by secretory antibodies is important in the defence against mucosal infections. Specific secretory immunoglobulin A (SIgA) can inhibit initial pathogen colonization by performing immune exclusion both on the mucosal surface and within virus-infected secretory epithelial cells without causing tissue damage. Resistance against toxin-producing bacteria such as Vibrio cholerae appears to be particularly dependent on SIgA antibodies. Like natural infections, live topical vaccines or adequate combinations of inactivated vaccines and mucosal adjuvants give rise not only to SIgA antibodies, but also to long-standing serum IgG and IgA responses. The intranasal route of vaccine application could be particularly attractive to achieve this result, but only if successful stimulation is obtained without the use of toxic adjuvants. The degree of protection after vaccination may range from complete inhibition of reinfection to reduction of symptoms. In this scenario it is generally difficult to determine unequivocally the relative importance of SIgA versus serum antibodies. However, infection models in knockout mice strongly support the notion that SIgA exerts a decisive role in protection and cross-protection against a variety of infectious agents.     

Regulation of the polymeric immunoglobulin receptor and IgA transport: new advances in environmental factors that stimulate pIgR expression and its role in mucosal immunity

Secretory IgA (SIgA) antibodies represent the first line of antigen-specific immune defense protecting the mucosal surfaces against environmental pathogens and antigens, and maintaining homeostasis with the commensal microbiota. The polymeric immunoglobulin receptor (pIgR) has the dual role of transporting locally produced dimeric IgA across mucosal epithelia, and serving as the precursor of secretory component, a glycoprotein that enhances the immune functions of SIgA. The complex regulation of pIgR expression and transcytosis by host and microbial factors is finely tuned to optimize the role of SIgA in mucosal immunity. Disruption of this regulatory network in disease states similar to inflammatory bowel disease can result in profound consequences for mucosal homeostasis and systemic sequelae. Future research into the function and regulation of pIgR and SIgA may offer new insights into the prevention and treatment of infectious and inflammatory diseases that originate at mucosal surfaces.     

IgA receptors in health and disease

The varied interaction of the Fc region of IgA with receptors confers this antibody class with many of its unique properties. The epithelial polymeric Ig receptor on mucosal epithelial cells transports polymeric immunoglobulin A (pIgA) produced by mucosal B cells to the mucosal surface where, in complex with the secretory component (SC), this secretory immunoglobulin A (SIgA) excludes the multitude of dietary, environmental, and microbial antigens that continuously bombard the mucosae. In health, this IgA-mediated exclusion not only forms the initial defence against infection, it also spares the systemic immune system from potentially deleterious responses to innocuous antigens which can otherwise culminate in inflammatory bowel disease or asthma. Beyond antigen exclusion, in closer encounters with antigens, IgA receptors play roles in protective immunity and disease. FcaRI is the principal myeloid IgA receptor and is responsible for differing IgA-mediated effector responses such as respiratory burst, degranulation, and phagocytosis variously by granulyoctes, monocytes, and macrophages. Furthermore an unknown IgA receptor specific for the secretory component (SC) elicits powerful effector responses from eosinophils. On dendritic cells, FcaRI participates in antigen presentation while on microfold cells, key cells in mucosal antigen presentation, another unknown IgA receptor functions in the transport of antigens across the mucosal epithelial barrier. The activity of another uncharacterized IgA1/IgD receptor on T cells may affect autoimmune disorders. The interplay of different IgA receptors affects immune complex deposition in the common renal disease immunoglobulin A nephropathy (IgAN). Finally, the therapeutic application of various IgA receptors has been sought in the areas of infectious disease, vaccines, and cancer.