Microbiota and Humoral Immunity

应用昆虫学报Chinese Journal of Applied Entomology 2013，50（5）：1203－1210．DOI ：10．7679/j．issn．2095－1353．2013．165檻檻檻檻檻檻檻檻檻檻檻檻殤殤殤殤科技前沿基于组学的寄生蜂与寄主免疫的相互作用*林哲1李建成2路子云2邹振1＊＊（1.中国科学院动物研究所农业虫害鼠害综合治理研究国家重点实验室北京100101；2.河北省农林科学院植物保护研究所农业部华北北部作物有害生物综合治理重点实验室河北省农业有害生物综合防治工程技术研究中心保定071000）摘要寄生蜂作为天敌昆虫，在害虫生物防治中起着极其重要的作用。

现代分子生物学和第二代测序技术的迅速发展，为筛选寄生蜂与寄主免疫互作的关键分子，阐明寄生蜂逃避或抑制寄主免疫系统攻击的机理提供了新的机遇。

昆虫的天然免疫可分为细胞免疫和体液免疫，寄生蜂在与寄主长期的协同进化过程中，依靠毒液（venom ）、多分DNA 病毒（PDV ）、类病毒颗粒（VLP ）、畸形细胞（teratocyte ）等手段，一方面调控寄主血细胞的增殖和分化，抑制细胞包囊反应，从而破坏寄主的细胞免疫系统；另一方面，通过抑制酚氧化酶原激活干扰寄主的体液免疫，从而逃避黑化反应的攻击。

寄生蜂在发育过程中也有相应的免疫防御机制。

本文从细胞免疫、体液黑化反应以及免疫信号通路等方面，综述了近年来利用组学手段在寄生蜂调控寄主免疫方面取得的最新进展，以期为阐明天然免疫的分子机制、探索害虫防治新方法提供借鉴。

关键词寄生蜂，免疫抑制，体液免疫，细胞免疫，黑化反应Immune aspects of interactions between parasitoid wasps and hostsLIN Zhe 1LI Jian-Cheng 2LU Zi-Yun 2ZOU Zhen 1＊＊（1.State Key Laboratory of Integrated Management of Pest Insects and Ｒodents ，Institute of Zoology ，Chinese Academy of Sciences ，Beijing 100101，China ；2.Institute of Plant Protection of Hebei Academy of Agriculture and Forestry Sciences ，IPM Center ofHebei Province ；Key Laboratory of Integrated Pest Management on Crops in Northern Ｒegion of North China ，Ministry ofAgriculture ，P．Ｒ．China ，Baoding 071000，China ）Abstract Parasitoid wasps ，as natural enemies of agricultural pests ，play important roles in biological pest control．Todate ，many studies have focused on identifying key molecules involved in parasitoid-host interactions．Insects have a potent innate immune system ，comprising cellular immunity and humoral immunity．Parasitoid wasps have evolved ways to evade or suppress these host defenses with venom proteins ，polydnavirus （PDV ），virus-like particles （VLP ），teratocytes and other virulent factors．The invasion of parasitoids reduces the total hemocyte count and suppresses hemocyte differentiation．Encapsulation ，an important cellular immune response ，can be inhibited by Ｒho family factors and calreticulin from parasitoid venom．Parasitoids evade host humoral immunity by interfering with Toll and IMD immune signaling pathways．Additionally ，host melanization is strongly inhibited by virulent factors．Through this review of the current literature ，we hope to provide new information on molecular aspects of parasitoid-host interactions ，which may lead to novel approaches for pest management．Key wordsparasitoid wasp ，immune suppression ，humoral immunity ，cellular immunity ，melanization*资助项目：国家自然科学基金项目（31272367）；国家重大科学研究计划（973项目）（2014CB139400）。

Microbial Ecology of the Gut and GutMicrobiomeThe microbial ecology of the gut and gut microbiome is a complex and fascinating area of study that has garnered increasing attention in recent years. The gut microbiome refers to the diverse community of microorganisms that reside in the gastrointestinal tract, playing a crucial role in human health and disease. This essay will explore the significance of the gut microbiome, its impact on human health, and the factors that influence its composition. The gut microbiome plays a vital role in human health, influencing various physiological processes such as digestion, metabolism, and immune function. It is involved in the breakdown of dietary components that are otherwise indigestible by the human body, producing essential nutrients and energy sources. Additionally, the gut microbiome interacts with the immune system, helping to maintain a balanced immune response and protect against pathogenic invaders. Furthermore, the gut microbiome has been linked to the development and function of the central nervous system, highlighting its influence beyond the gastrointestinal tract. The composition of the gut microbiome is influenced by a multitude of factors, including genetics, diet, age, and environmental exposures. For example, studies have shown that the gut microbiome of individuals consuming a plant-based diet differs significantly from those consuming an animal-based diet. Additionally, the use of antibiotics and other medications can disrupt the balance of the gut microbiome, leading to potential health consequences. Understanding the factors that shape the gut microbiome is crucial in developing strategies to maintain a healthy microbial community within the gut. Imbalances in the gut microbiome, known as dysbiosis, have been associated with various health conditions, including inflammatory bowel diseases, obesity, and metabolic disorders. Research has shown that restoring a healthy gut microbiome through interventions such as probiotics, prebiotics, and fecal microbiota transplantation can have beneficial effects on these conditions. This highlights the potential for manipulating the gut microbiome as a therapeutic approach for improving human health. In conclusion, the gut microbiome plays a fundamental role in human health and disease, influencing various physiologicalprocesses and interacting with the immune system. Understanding the factors that shape the gut microbiome and its impact on health is crucial in developing strategies to maintain a healthy microbial community within the gut. Moreover, the potential for manipulating the gut microbiome as a therapeutic approach underscores the significance of ongoing research in this field.。

The Gut MicrobiotaREVIEWInteractions Between the Microbiota and the Immune SystemLora V.Hooper,1*Dan R.Littman,2Andrew J.Macpherson 3The large numbers of microorganisms that inhabit mammalian body surfaces have a highly coevolved relationship with the immune system.Although many of these microbes carry out functions that are critical for host physiology,they nevertheless pose the threat of breach with ensuing pathologies.The mammalian immune system plays an essential role in maintaining homeostasis with resident microbial communities,thus ensuring that the mutualistic nature of the host-microbial relationship is maintained.At the same time,resident bacteria profoundly shape mammalian immunity.Here,we review advances in our understanding of the interactions between resident microbes and the immune system and the implications of these findings for human health.Complex communities of microorganisms,termed the “microbiota,”inhabit the body surfaces of virtually all vertebrates.In the lower intestine,these organisms reach extraordi-nary densities and have evolved to degrade a variety of plant polysaccharides and other dietary substances (1).This simultaneously enhances host digestive efficiency and ensures a steady nutrient supply for the microbes.Metabolic efficiency was likely a potent selective force that shaped the evolution of both sides of the host-microbiota lions of years of coevolution,however,have forged pervasive interconnections between the physiologies of microbial commu-nities and their hosts that extend beyond metabolic functions.These interconnections are particularly apparent in the relationship between the microbiota and the immune system.Despite the symbiotic nature of the intestinal host-microbial relationship,the close association of an abundant bacterial community with intesti-nal tissues poses immense health challenges.The dense communities of bacteria in the lower intes-tine (≥1012/cm 3intestinal contents)are separated from body tissues by the epithelial layer (10m m)over a large intestinal surface area (~200m 2in humans).Opportunistic invasion of host tissue by resident bacteria has serious health consequences,including inflammation and sepsis.The immune system has thus evolved adaptations that work to-gether to contain the microbiota and preserve the symbiotic relationship between host and microbiota.The evolution of the vertebrate immune system has therefore been driven by the need to protect thehost from pathogens and to foster complex micro-bial communities for their metabolic benefits (2).In this Review,we survey the state of our understanding of microbiota-immune system in-teractions.We also highlight key experimental challenges that must be confronted to advance our understanding in this area and consider how our knowledge of these interactions might be harnessed to improve public health.Tools for Analyzing the Microbiota –Immune System RelationshipMuch of our current understanding of microbiota –immune system interactions has been acquired from studies of germ-free animals.Such animals are reared in sterile isolators to control their exposure to microorganisms,including viruses,bacteria,and eukaryotic parasites.Germ-free animals can be studied in their microbiologically sterile state or can serve as living test tubes for the establishment of simplified microbial ecosystems composed of a single microbial species or defined species mixtures.The technology has thus come to be known as “gnotobiotics,”a term derived from Greek meaning “known life.”Gnotobiotic ani-mals,particularly rodents,have become critical experimental tools for determining which host immune functions are genetically encoded and which require interactions with microbes.The current impetus for gnotobiotic exper-imentation has been driven by several impor-tant technical advances.First,because any mouse strain can be derived to germ-free status (3),large numbers of genetically targeted and wild-type inbred isogenic mouse strains have become avail-able in the germ-free state.The contribution of different immune system constituents to host-microbial mutualism can thus be determined by comparing the effects of microbial colonization in genetically altered and wild-type mice (4,5).Second,next-generation sequencing tech-nologies have opened the black box of micro-biota complexity.Although advances in ex vivo culturability are still needed,the composition ofhuman and animal microbiotas can be opera-tionally defined from polymorphisms of bacterial genes,especially those encoding the 16S ribo-somal RNA sequences.Such analyses have made possible the construction of defined microbiotas,whose distinct effects on host immunity can now be examined (6).Moreover,these advances allow the study of experimental animals that are both isobiotic and,in a defined inbred host,isogenic.A dominant goal of these efforts is to benefit hu-man health [see Blumberg and Powie (7)].With the developing technology,the species differ-ences can be closed using mice with a defined humanized microbiota (8).On the horizon,there is even the prospect of humanized isobiotic mice that also have a humanized immune system (9).A third advance has been the development of experimental systems that allow the uncoupling of commensal effects on the immune system from microbial colonization.This cannot be achieved by antibiotic treatment alone because a small pro-portion of the targeted microbes will persist.Deletion strains of bacteria lacking the ability to synthesize prokaryotic-specific amino acids have been developed that can be grown in culture but do not persist in vivo,so the animals become germ-free again.This allows issues of mucosal immune induction,memory,and functional protection to be explored without permanent colonization (10).Finally,important insights about the impact of resident microbial communities on mammalian host biology have been acquired by using high-throughput transcriptomic and metabolomic tools to compare germ-free and colonized mice (11,12).These tools include DNA microarrays,which have led to a detailed understanding of how microbiota shape many aspects of host physiology,includ-ing immunity (13,14)and development (15),as well as mass spectrometry and nuclear magnetic resonance spectroscopy,which have provided im-portant insights into how microbiota influence metabolic signaling in mammalian hosts (12).The application of these new approaches to the older technology of gnotobiotics has revolutionized the study of interactions between the microbiota and the immune system.Looking Inside-Out:Immune System Control of the MicrobiotaA major driving force in the evolution of the mammalian immune system has been the need to maintain homeostatic relationships with the microbiota.This encompasses control of micro-bial interactions with host tissues as well as the composition of microbial consortia.Here,we dis-cuss recent insights into how the immune system exerts “inside-out ”control over microbiota local-ization and community composition (see Fig.1).Stratification and compartmentalization of the microbiota.The intestinal immune system faces unique challenges relative to other organs,as it must continuously confront an enormous micro-bial load.At the same time,it is necessary to avoid1The Howard Hughes Medical Institute and Department of Im-munology,The University of Texas Southwestern Medical Center at Dallas,Dallas,TX 75390,USA.2Howard Hughes Medical Institute and Molecular Pathogenesis Program,The Kimmel Center for Biology and Medicine of the Skirball Institute,New York University School of Medicine,New York,NY 10016,USA.3Maurice Müller Laboratories,University Clinic for Visceral Sur-gery and Medicine,University of Bern,Bern,Switzerland.*To whom correspondence should be addressed.E-mail:lora.hooper@8JUNE 2012VOL 336SCIENCE1268 o n M a y 20, 2015w w w .s c i e n c e m a g .o r g D o w n l o a d e d f r o mpathologies arising from innate immune signaling or from microbiota alterations that disturb essential metabolic functions.An important function of the intestinal immune system is to control the expo-sure of bacteria to host tissues,thereby lessening the potential for pathologic outcomes.This oc-curs at two distinct levels:first,by minimizing direct contact between intestinal bacteria and the epithelial cell surface(stratification)and,second, by confining penetrant bacteria to intestinal sites and limiting their exposure to the systemic im-mune compartment(compartmentalization).Several immune effectors function together to stratify luminal microbes and to minimize bacterial-epithelial contact.Intestinal goblet cells secrete mucin glycoproteins that assemble into a~150-m m-thick viscous coating at the intestinal epithelial cell surface.In the colon,there are two structurally distinct mucus layers.Although the outer mucus layer contains large numbers of bacteria,the inner mucus layer is resistant to bacterial penetration (16).In contrast,the small intestine lacks clearly distinct inner and outer mucus layers(17).Here, compartmentalization depends in part on antibac-terial proteins that are secreted by the intestinal epithelium.RegIII g is an antibacterial lectin that is expressed in epithelial cells under the control of Toll-like receptors(TLRs)(18–20).RegIII g limits bacterial penetration of the small intestinal mucus layer,thus restricting the number of bacteria that contact the epithelial surface(5).Stratification of intestinal bacteria on the luminal side of the epithelial barrier also depends on secreted immunoglobulin A(IgA).IgA spe-cific for intestinal bacteria is produced with the help of intestinal dendritic cells that sample the small numbers of bacteria that penetrate the over-lying epithelium.These bacteria-laden dendritic cells interact with B and T cells in the Peyer’s patches,inducing B cells to produce IgA directed against intestinal bacteria(21).IgA+B cells home to the intestinal lamina propria and secrete IgA that is transcytosed across the epithelium and deposited on the apical surface.The transcytosed IgAs bind to luminal bacteria,preventing micro-bial translocation across the epithelial barrier(22).Mucosal compartmentalization functions to minimize exposure of resident bacteria to the sys-temic immune system(Fig.1B).Although bacteria are largely confined to the luminal side of the epithelial barrier,the sheer number of intestinal bacteria makes an occasional breach inevita-ble.Typically,commensal microorganisms that penetrate the intestinal epithelial cell barrier are phagocytosed and eliminated by lamina propria macrophages(23).However,the intestinal im-mune system samples some of the penetrant bac-teria,engendering specific immune responses that are distributed along the length of the intes-tine(21).Bacteria that penetrate the intestinal barrier are engulfed by dendritic cells(DCs)re-siding in the lamina propria and are carried alive to the mesenteric lymph nodes.However,these bacteria do not penetrate to systemic secondarylymphoid tissues.Rather,the commensal-bearingDCs induce protective secretory IgAs(21),whichare distributed throughout all mucosal surfacesby recirculation of activated B and T cells.Thus,distinctive anatomical adaptations in the mucosalimmune system allow immune responses directedagainst commensals to be distributed widely whilestill being confined to mucosal tissues.Other immune cell populations also promotethe containment of commensal bacteria to in-testinal sites.Innate lymphoid cells reside in thelamina propria and have effector cytokine pro-files resembling those of T helper(T H)cells(24).Innate lymphoid cells that produce interleukin(IL)–22are essential for containment of lymphoid-resident bacteria to the intestine,thus preventingtheir spread to systemic sites(25).The compartmentalization of mucosal andsystemic immune priming can be severely per-turbed in immune-deficient mice.For example,mice engineered to lack IgA show priming ofserum IgG responses against commensals,indi-cating that these bacteria have been exposed tothe systemic immune system(22).A similar out-come is observed when innate immune sensingisFig.1.Looking inside-out:immune system control of the microbiota.Several immune effectors function together to stratify luminal microbes and to minimize bacterial-epithelial contact.This includes the mucus layer,epithelial antibacterial proteins,and IgA secreted by lamina propria plasma partmen-talization is accomplished by unique anatomic adaptations that limit commensal bacterial exposure to the immune system.Some microbes are sampled by intestinal DCs.The loaded DCs traffic to the mesenteric lymph nodes through the intestinal lymphatics but do not penetrate further into the body.This compartmentalizes live bacteria and induction of immune responses to the mucosal immune system. There is recirculation of induced B cells and some T cell subsets through the lymphatics and the bloodstream to home back to mucosal sites,where B cells differentiate into IgA-secreting plasma cells. SCIENCE VOL3368JUNE20121269SPECIAL SECTIONThe Gut Microbiotadefective.Mice lacking MyD88or TRIF signal-ing adaptors for TLR-mediated sensing of bacteria also produce serum IgG responses against com-mensals(26).This probably results from the fact that in these settings,large numbers of commensals cross the epithelial barrier and phagocytic cells are less able to eliminate the penetrant organisms.Immune system control of microbiota com-position.The development of high-throughput sequencing technologies for microbiota analysis has provided insight into the many factors that determine microbiota composition.For example nutrients,whether derived from the host diet (27)or from endogenous host sources(28),are critically important in shaping the structure of host-associated microbial communities.Recent evidence suggests that the immune system is also likely to be an important contributor to“inside-out”host control over microbiota composition.Certain secreted antibacterial proteins produced by epithelial cells can shape the composition of in-testinal microbial communities.a-defensins are small(2to3kD)antibacterial peptides secreted by Paneth cells of the small intestinal epithelium.Anal-ysis of the microbiota in mice that were either de-ficient in functional a-defensins or that overexpressed human a-defensin-5showed that although there was no impact on total numbers of colonizing bacte-ria,there were substantial a-defensin–dependent changes in community composition,with reciprocal differences observed in the two mouse strains(29).An interesting question is how far secreted in-nate immune effectors“reach”into the luminal microbial consortia.For example,the impact of hu-man a-defensin-5on luminal community composi-tion contrasts with the antibacterial lectin RegIII g, which limits penetration of bacteria to the epithelial surface but does not alter luminal communities(5). This suggests that some antimicrobial proteins,such as a-defensins,reach into the lumen to shape overall community composition,whereas others,such as RegIII g,have restricted effects on surface-associated bacteria and thus control microbiota location relative to host surface tissues.Questions remain as to ex-actly how a-defensin-5controls luminal community composition,however.In one scenario,these small antimicrobial peptides diffuse through the mucus layer and directly act on bacteria that inhabit the lu-men.Another possibility is that a-defensin-5exerts its antibacterial activity on bacteria that are trapped in the outer reaches of the mucus layer,with those bac-teria acting as reservoirs that seed luminal commu-nities and thus dictate their composition.Answering these questions will require improved tools for fine-mapping microbiota composition and consortia from the surface of the intestine to the interior of the lumen.The impact of the immune system on micro-biota composition is also suggested by several im-mune deficiencies that alter microbial communities in ways that predispose to disease.For example, Garrett et al.studied mice that lack the transcription factor T-bet(encoded by Tbx21),which governs inflammatory responses in cells of both the innate and the adaptive immune system(30).WhenTbx21–/–mice were crossed onto Rag2–/–mice,which lack adaptive immunity,the Tbx21–/–/Rag2–/–progeny developed ulcerative colitis in a microbiota-dependent manner(30).Remarkably,this colitisphenotype was transmissible to wild-type mice byadoptive transfer of the Tbx21–/–/Rag2–/–micro-biota.This demonstrated that altered microbiotawere sufficient to induce disease and could thus beconsidered“dysbiotic.”Similarly,mice lacking thebacterial flagellin receptor TLR5exhibit a syn-drome encompassing insulin resistance,hyper-lipidemia,and increased fat deposition associatedwith alterations in microbiota composition(31).These metabolic changes are transferable to wild-type mice that acquire the Tlr5–/–gut microbiota.A third example of immune-driven dysbiosis isseen in mice deficient for epithelial cell expres-sion of the inflammasome component NLRP6.These mice develop an altered microbiota withincreased abundance of members of the Bacte-roidetes phylum associated with increased intes-tinal inflammatory cell recruitment and susceptibilityto chemically induced colitis.Again,there is evi-dence that dysbiosis alone is sufficient to drive theintestinal inflammation,because conventionallyraised wild-type mice that acquire the dysbioticmicrobiota show similar immunopathology(32).Together,these findings suggest that the im-mune system affords mammalian hosts some con-trol over the composition of their resident microbialcommunities.It is also clear that these commu-nities can be perturbed by defects in the host im-mune system.This leads to the idea of the immunesystem as a form of ecosystem management thatexerts critical control over microbiota compo-sition,diversity,and location[see Costello et al.(33)].However,a number of questions remain.First,although it is apparent that the immune sys-tem shapes community composition at the specieslevel,it is not yet clear whether the immune sys-tem shapes the genetics and physiology of indi-vidual microbial species.Second,how much doesthe immune system combine with gastric acid andintestinal motility to control the longitudinal dis-tribution of microbial species in the gastrointes-tinal tract?Finally,it will be important to determinethe extent to which the immune system also con-trols microbial community composition and loca-tion in other organ systems,such as the respiratorytract,urogenital tract,and skin.Looking Outside-In:How MicrobiotaShape ImmunityThe earliest comparisons of germ-free and colonizedmice revealed a profound effect of microbial colo-nization on the formation of lymphoid tissues andsubsequent immune system development.It wasthus quickly apparent that the microbiota influ-ence the immune system from“outside-in.”Recentstudies have greatly amplified this understandingand have revealed some of the cellular and mo-lecular mediators of these interactions(see Fig.2).The impact of the microbiota on lymphoidstructure development and epithelial function.The tissues of the gastrointestinal tract are rich inmyeloid and lymphoid cells,many of whichreside in organized lymphoid tissues.It has longbeen appreciated that the gut microbiota have acritical role in the development of organized lym-phoid structures and in the function of immunesystem cells.For example,isolated lymphoid fol-licles in the small intestine do not develop ingerm-free mice,and such mice are also deficientin secretory IgA and CD8ab intraepithelial lym-phocytes.The specific microbial molecules en-dowed with this inductive function have not yetbeen described,however.Sensing of commensal microbiota through theTLR-MyD88signaling pathway triggers severalresponses that are critical for maintaining host-microbial homeostasis.The microbiota inducerepair of damaged intestinal epithelium through aMyD88-dependent process that can be rescued inmicrobe-depleted animals by gavage with bacteriallipopolysaccharide(LPS).The innate signals,con-veyed largely through myeloid cells,are required toenhance epithelial cell proliferation(34,35).Asdiscussed above,MyD88-dependent bacterial sig-nals are also required for the induction of epithelialantimicrobial proteins such as RegIII g(5,19).Thisexpression can be induced by LPS(19,20)or flagel-lin(36).The flagellin signals are relayed throughTLR5expressed by CD103+CD11b+dendritic cellsin the lamina propria,stimulating production of IL-23that,in turn,promotes the expression of IL-22by innate lymphoid cells(37).IL-22then stimu-lates production of RegIII g,which is also secretedupon direct activation of MyD88in epithelialcells(5,20).This is one clear example of theimportance of commensals in the induction of hostinnate responses,but it likely represents a tinyfraction of the multitude of effects of microbiota onthe host immune system.Microbiota shaping of T cell subsets.It hasrecently become evident that individual commensalspecies influence the makeup of lamina propria Tlymphocyte subsets that have distinct effector func-tions.Homeostasis in the gut mucosa is maintainedby a system of checks and balances between poten-tially proinflammatory cells,which include T H1cellsthat produce interferon-g;T H17cells that produceIL-17a,IL-17f,and IL-22;diverse innate lymphoidcells with cytokine effector features resemblingT H2and T H17cells;and anti-inflammatory Foxp3+regulatory T cells(T regs).Colonization of mice withsegmented filamentous bacteria(SFB)results inaccumulation of T H17cells and,to a lesser extent,inan increase in T H1cells(38,39).SFB appear able topenetrate the mucus layer overlying the intestinalepithelial cells in the terminal ileum,and they in-teract closely with the epithelial cells,inducing hostcell actin polymerization at the site of interactionand,presumably,signaling events that result in aT H17polarizing environment within the laminapropria.There is little known about host cell8JUNE2012VOL336SCIENCE 1270signaling pathways initiated by SFB.It is possible that SFB influence epithelial gene expression,re-sulting,for example,in expression of antimicro-bial proteins such as RegIII g and of molecules that participate in T H 17cell polarization.SFB may also act directly on cells of the immune sys-tem,either through interactions with myeloid cells that extend processes through the epithelium to the mucus layer or by production of metabolites that act on various receptors expressed by host cells.Other bacteria have been shown to enhance the anti-inflammatory branches of the adaptive immune system by directing the differentiation of T regs or by inducing IL-10expression.For example,coloniza-tion of gnotobiotic mice with a complex cocktail of 46mouse Clostridial strains,originally isolated from mouse feces and belonging mainly to cluster IVand XIV a of the Clostridium genus,results in the expansion of lamina propria and systemic T regs .These have a phenotype characteristic of T regs in-duced in the periphery in response to transforming growth factor (TGF)–b and retinoic acid [in contrast to thymic-derived natural (n)T regs (40)],and manyof these inducible T regs (iT regs )express IL-10.The exact Clostridial strains within the complex exper-imental mixture that drive this regulatory response remain to be defined.Furthermore,polysaccharide A (PSA)of Bacteroides fragilis induces an IL-10response in intestinal T cells,which prevents the expansion of T H 17cells and potential damage to the mucosal barrier (41).In contrast,mutant B.fragilis lacking PSA has a proinflammatory profile and fails to induce IL-10.Production of PSA by B.fragilis has been proposed to be instrumental for the bac-terium ’s success as a commensal.Within the intestine,the balance of effector lym-phoid cells and T reg cells can have a profound in-fluence on how the mucosa responds to stresses that elicit damage.The relative roles of commensal-regulated Tcells differ according to the models used to study inflammation.For example,in mice sub-jected to chemical or pathogen-induced damage to the mucosa,T H 17cells have a beneficial effect that promotes healing.In contrast,T H 1and T H 17cells,as well as IL-23–dependent innate lymphoid cells,promote colitis in models in which T reg cells aredepleted.It is likely that inflammatory bowel dis-eases in humans can be similarly triggered by commensal-influenced imbalance of lymphoid cell subsets.This is supported by numerous observations,including the strong linkage of IL23R polymor-phisms with Crohn ’s disease,a serious condition with relapsing intestinal inflammation and a risk of malignancy,and the severe enterocolitis associated with IL10and IL10R mutations (42,43).Microbiota effects on systemic immunity.The influence of commensal bacteria on the balance of T cell subsets is now known to extend well beyond the intestinal lamina propria.Homeostatic T cell proliferation itself is driven by the microbiota or their penetrant molecules (44).Systemic auto-immune diseases have long been suggested to have links to infections,but firm evidence for causality has been lacking.Recent studies in animal models,however,have reinforced the notion that commen-sal microbiota contribute to systemic autoimmune and allergic diseases at sites distal to the intestinal mucosa.Several mouse models for autoimmunity are dependent on colonization status.Thus,germ-free mice have marked attenuation of disease in models of arthritis and experimental autoimmune encephalomyelitis (EAE),as well as in various colitis models.In models of T H 17cell –dependent arthritis and EAE,monoassociation with SFB is sufficient to induce disease (42,45,46).In all of these models,induction of T H 17cells in the in-testine has a profound influence on systemic dis-ease.Exacerbation of arthritis and EAE is likely the consequence of an increase in the number of arthritogenic or encephalitogenic T H 17cells that traffic out of the lamina propria.The antigen spec-ificity of such cells remains to be examined.Induction of iT regs by the cluster IV and XIV a Clostridia also has a systemic effect on inflamma-tory processes.Colonization of germ-free mice with these bacteria not only results in attenuated disease after chemical damage of the gut epithelium but also reduces the serum IgE response after immuni-zation with antigen under conditions that favor a T H 2response (40).As with pathogenic T H 17cells,the antigen specificity of the commensal-induced iT regs that execute systemic anti-inflammatory func-tions is not yet known,although at least some of the T regs in the gut have Tcell receptors with specificity for distinct commensal bacteria (47).Finally,B.fragilis PSA affects the develop-ment of systemic T cell responses.Colonization of germ-free mice with PSA-producing B.fragilis results in higher numbers of circulating CD4+T cells compared to mice colonized with B.fragilis lacking PSA.PSA-producing B.fragilis also elicits higher T H 1cell frequencies in the circulation (48).Together,these findings show that commen-sal bacteria have a general impact on immunity that reaches well beyond mucosal tissues.Microbiota influences on invariant Tcells and innate lymphoid cells.A recent study extends the role of microbiota to the control of the function invariant natural killer T cells (iNKT cells),whichFig.2.Looking outside-in:how microbiota shape host immunity.Some of the many ways that intestinal microbiota shape host immunity are depicted.These include microbiota effects on mucosal as well as systemic immunity.ILFs,isolated lymphoid follicles.SCIENCEVOL 3368JUNE 20121271SPECIAL SECTION。

《医学免疫学与微生物学》试题及答案（Examination questions and answers of medical immunology and Microbiology）Examination questions and answers of medical immunology and MicrobiologyFirst, fill in the blanks (1 points per minute, 15 points)1. normal immune function showed _______________, such as the low level can lead to __________________.The 2. is ____________ and lack of ____________ substance called semi antigen.Two features of class I and class II gene gene 3. classic is __________________ and ___________________.4.CK usually in ___________ way to produce CK cells themselves, or to ___________ effects on neighboring cells.5.TCR-CD3 complex, the function of TCR is ________________, CD3 molecules through the ______________ structure in the cytoplasm, the antigen signal transduction into cells.6. bacterial structure lacks _____________, known as the L type of bacteria.The 7. main ______________ caused by typhoid fever.8. of avian influenza virus subtype is ________________.The 9. is _________________ pathogenic hantavirus.10. chemical composition of bacterial endotoxin is______________.Two, interpretation of the term (every day 3 points, a total of 15 points)1. antigen2. monoclonal antibody3. cytokines4. sepsis5. micro ecological imbalanceThree, RadioButtonList: from the following A, B, C, D 4 answers, choose 1 correct answers and the English letters in parentheses (match each 1 points, a total of 30 points)1. adaptive immunity is characterized by ()A. comes with birthB. reacts quicklyC. specificityD. without memory2. in the following description of the toxin, the error is ()A. toxoid is made from immune serum of immunized animalsB. should be done skin test before injectionC. can neutralize the toxin, may cause hypersensitivityD. is used for artificial immunity3. which of the following elevated Ig may indicate a recent infection of the body?A.IgGB.IgMC.IgED.IgA4. the elevated complement component in the serum of patients with hereditary vascular edema is ()A.C1qB.C2aC.C4aD.C95. the component of complement cleavage, which has both the action of accommodation and the action of immune adherence, is ()A.C2aB.C2bC.C5bD.C3b6. the following description of MHC is correct except ()A. a tightly linked genetic groupThe MHC of the B. is called the HLA complexThe C.HLA complex is located on chromosome seventeenthD. and cell recognition and the presentation of antigen peptide to T cells7., according to the genetic rule of the unit type, the probability of the same 2 parts of a sibling is equalA.0%B.25%C.50%D.100%8.HLA class II molecules are mainly expressed in ()A. dendritic cellsB. neutrophilsC.T cellD.NK cellThe function of 9. cytokines is ()A. specificityB. is limited by MHCC. plays a role through cytokine receptorsD. mainly functions as endocrine form10. for the description of the T cell activation second signal, the error is ()A. is also called cooperative stimulation signalB.Antigen specificC., if there is no second signal, T cells become incompetentThe combination of D. and CD28 molecules with B7 molecules is the most important second signal11., the erroneous description of NK cells is ()A. cell containing azurophilic granules. It is also called the large granular lymphocytesB. can kill some tumor cells directlyC. can also kill target cells through ADCCD. target cell is limited by MHC12., the so-called TCR antigen recognition refers to () Identification of A. TCR against primary peptides Identification of MHC molecules by B. and TCRDouble recognition of MHC: antigen peptide by C. and TCR Identification of complete antigen molecules by D. TCRThe characteristics of 13.CD8+CTL target cell are ()A. antigen free specificityB. is restricted by MHC class II moleculesC. target cells undergo lysis and apoptosisD. CTL itself is also damaged14. in type IV hypersensitivity, CD4+T cells mediate inflammatory responses, and the major inflammatory cells are ()A. macrophagesB.NK cellC. neutrophilsD.CTL15. again, the significance of antibody response in medical practice is ()A. vaccination more than two timesWhen B. serology tests for infectious diseases, they should be done at the beginning of the disease and the recovery stage, and the results are comparedC. serological diagnosis should identify nonspecific recall reactionsMore than D., all rightType 16. hypersensitivity is characterized by ()A. is mediated by antibody IgGB. damages target cells by complement and NK cellsC. does not cause tissue damageD. has obvious individual difference and genetic predisposition17. in the description of heterologous immune serum desensitization therapy, the mistake is ()A. is suitable for individuals who have been identified with allergen and are difficult to avoid contact with this allergenB. uses small doses, short intervals, and multiple injectionsC. target cells in batches desensitization, and finally sensitized state all liftedD. desensitization is temporary18. tuberculin test positive indicated ()A. has never been exposed to Mycobacterium tuberculosisB. is suffering from severe TBC. has been infected with TB and has acquired the cellular immunity against Mycobacterium tuberculosisD. has antibodies against Mycobacterium tuberculosis in vivo19., the patient's repeated local injection of insulin caused local redness, bleeding, and necrosis, and the hypersensitivity associated with this was ()Type A. hypersensitivityType B. hypersensitivityType C. hypersensitivityType D. hypersensitivity20. newborns can acquire naturally passive immunity from the mother's IgA.IgG and IgMB.IgG and SIgAC.IgA and IgMD.IgD and IgE21. the virus that produces only transient immunity afterinfection is ()A. measles virusB. Japanese encephalitis virusC. hepatitis C virusD. influenza virus22. the major bacteria associated with acute glomerulonephritis are ()Group A.A StreptococcusB. Escherichia coliCoagulase positive staphylococci C.D. coagulase negative staphylococci23. the causative substance of Clostridium difficile is mainly ()A. endotoxinExotoxin B.C. capsuleD. fimbriae24. microorganisms that are ineffective in the treatment of antibiotics are ()Mycoplasma A.Chlamydia B.C. virusD. fungi25. among the following descriptions of hepatitis A virus, the error is ()A. only causes acute infectionB. has strong resistance to the outside worldC. has a capsuleD. vaccine has a good preventive effect26. in the following description of the HIV feature, the error is ()The A. virus contains reverse transcriptaseB. has strong resistance to the outside worldC. has a capsuleD. is mainly infected with Th cells and macrophages27. microorganisms causing thrush are ()Yersinia pestis A.B. Candida albicansC. Helicobacter pyloriLeptospira D.28. in the following viruses, the nucleic acid is DNA and is ()A. hepatitis A virusB. hepatitis B virusC. rabies virusD.SARS coronavirus29. the following substances, which can be made into toxoid after formaldehyde treatment, are ()A. antibioticB. endotoxinC. antitoxinExotoxin D.30. irregular use of antibiotics can lead to antibiotic associated diarrhoea and pseudomembranous colitis, the pathogen is ()A. Candida albicansClostridium perfringens B.Clostridium difficile, C.Bacillus anthracis D.Four, to: (2 points per day, a total of 16 points)Answer the following questions: 1) note that the narrative is wrong, please carefully read each question and find out the error; 2) will be described below in the correct question blank in must not change in question; 3) according to the answer, the answer is not simple or not, or not. Is not the "noun", should express the correct meaning, nor "terminology".1. modern immunization believes that the result of an immune response is always beneficial to the organism.Corrections：A polysaccharide or protein antigen between 2. hemolyticstreptococci and a common antigen between the human colon mucosa.Corrections：3. the three activation pathways of complement have different end pathways.Corrections：4. the immune cells in quiescent state and activated state can secrete CK.Corrections：5. thymic cells obtained by positive selection have the ability to tolerate themselves.Corrections：6. in activated CD4+T cells released by CK, IL-2 is a powerful activator of monocytes / macrophages.Corrections：7. all anaerobic bacteria have spores, all of which are gram positive bacteria, all of which are bacilli.Corrections：8. Mycobacterium tuberculosis on ultraviolet light, alcohol,boiling resistance is strong, not easy to kill.Corrections：Five questions (8 points per day, a total of 24 points)What are the biological effects of 1. cell immunity?2. why can HLA genotype and / or phenotype be used in individual identification and paternity testing?3. what are the mechanisms of immune pathology mediated by cellular and humoral immunity in hepatitis B?。

The worldwide epidemic of obesity and related metabolic diseases is spreading rap-idly and has become a serious problem not only for individual health but also for fami-lies and society in general1–6(BOX 1). Excessive fat accumulation and insulin resistance are the two main pathological phenotypes of obesity, which is also associated with a low-grade systemic and chronic inflammatory condition7. Obesity can increase the risk of a wide array of chronic diseases, such as dia-betes and cardiovascular disease. The rapid increase in obesity over the past few decades cannot be effectively explained by changes in human genetics2,8. Instead, a high-caloric diet and sedentary lifestyle seem to be among the primary driving forces; however, the pathological molecular processes that link a poor diet to obesity are still poorly defined9. Furthermore, the key mediators that are essential checkpoints for the development of obesity and so could potentially be targeted for prevention and therapy are also largely unknown. A paradigm shift in our view of the structure and function of the human body is needed to effectively manage the ongoing epidemic of obesity.In recent years, there has been a growing appreciation for the fact that, as humans, we are in fact supraorganisms composed of both human and microbial cells10, and as such we carry two sets of genes, those encoded inour own genome and those encoded in ourmicrobiota (FIG. 1). The total complementof the former is ~23,000 genes11, whereasthe latter, called the microbiome, comprises~3 million genes12,13. Thus, as supraorgan-isms, we genetically inherit only ~1% of ourgenes from our parents, and the remaining~99% is mainly acquired from the immedi-ate environment when we are born, and inparticular from our mother’s birth canal andbreast milk14–23. Importantly, all the genes inour body, whether human or microbiomeencoded, have the potential to have an impacton our health24,25.The gut is the most densely colonizedmicrobial community in the human bodyand is also one of the most diverse26,27. Thegut functions as a chemostat, a continuousculture system for microorganisms (mostlybacteria) in which fresh nutrients enter thesystem and cultured microorganisms leaveat a relatively constant rate28. Approximately1.5 kg of bacteria are resident in our gut25,and 50% of our faecal matter biomass isbacterial cells. To maintain such a highpopulation density, these bacteria need alot of nutrients, which can come from foodsources such as dietary fibres (which areotherwise indigestible to humans)29,30, mucinand cells sloughed from the gut29,31, as well asdrugs and other xenobiotic compounds thatenter the gut32,33. Host digestive physiology,including the pH of the gut and the pres-ence of bile acids34,35, and components of theinnate immune response, such as defensinsand immunoglobulin A, impose a selectivepressure to determine the membership ofthe gut microbiota — that is, which strainscan colonize the gut — from early life36 .However, the population level that a residentstrain can reach and maintain is a result ofthe equilibrium between the ability of thatstrain to take advantage of the availablenutrients for reproduction and its ability towithstand the forces removing it from thegut37. Diet has been shown to be the majorforce in shaping the composition of the gutmicrobiota38–40.Metabolites produced by gut bacteriacan enter the bloodstream by absorption,enterohepatic circulation or impaired gutbarrier function41. Indeed, up to one-thirdof the small molecules in human bloodcan be derived from gut bacteria42,43. Somemicrobiota-derived metabolites can have apositive impact on the host, including thosewith anti-inflammatory activity44, antioxi-dant activity45 and pain relief activity46, aswell as those acting as vitamins47 or energysources48 and those that regulate gut barrierfunction49. For example, butyrate, whichis produced by bacterial fermentation ofdietary fibres, can serve as an energy sourcefor colonocytes and can increase satiety50,51.This compound is also effective in alleviat-ing inflammation, reducing carcinogenesis,mitigating oxidative stress and improvinggut barrier function49,52. By contrast, othermicrobiota-derived metabolites are toxicto their host, including cytotoxins53, geno-toxins54 and immunotoxins55. For example,lipopolysaccharide (LPS), an endotoxinreleased by Gram-negative bacteria, canprovoke an inflammatory response and thusaggravate inflammation-related chronicconditions such as adiposity and insulinresistance52,55,56.As most of the incidence of obesity isattributed to diet, recent efforts to combatobesity and related metabolic diseases havefocused on whether the gut microbiota hasa role as a mediator that can predisposethe host to diet-induced obesity and, if so,O P I N I O NThe gut microbiota and obesity:from correlation to causalityLiping ZhaoAbstract | The gut microbiota has been linked with chronic diseases such as obesityin humans. However, the demonstration of causality between constituents of themicrobiota and specific diseases remains an important challenge in the field. In thisOpinion article, using Koch’s postulates as a conceptual framework, I explore thechain of causation from alterations in the gut microbiota, particularly of the endo-toxin-producing members, to the development of obesity in both rodents andhumans. I then propose a strategy for identifying the causative agents of obesity inthe human microbiota through a combination of microbiome-wide associationstudies, mechanistic analysis of host responses and the reproduction of diseasesin gnotobiotic animals.PERSPECTIVES NATURE REVIEWS |MICROBIOLOGY VOLUME 11 | SEPTEMBER 2013 |639how we can identify the key obesity-related microorganisms in the gut. Since their estab-lishment more than 100 years ago, Koch’s postulates have been modified for the identification of causative agents not only for infectious diseases but also for non-infectious diseases57. In this Opinion article, using Koch’s postulates as the conceptual framework (BOX 2), I synthesize the evidence that demonstrates a causative role for the gut microbiota, particularly the endotoxin-producing members, in the development of obesity in both rodent models and humans.I then propose a top-down strategy25 for identifying further members of the micro-biota with a causative role in human obesity and related metabolic diseases.The whole microbiota as a ‘pathogen’If the whole gut microbiota has a causative role — that is, functions as a pathogen-like entity (BOX 2) — in the onset and progression of obesity and its sequelae, experimental manipulation of the microbiota (for example, removing or adding it back to animal hosts, or transferring it between lean and obese individuals) should change host obesity-related phenotypes, in particular adiposity and insulin resistance57. Conventionalization of germ-free mice. Carrying out such microbiota manipulation studies in humans is difficult, if not impos-sible, for both technical and ethical reasons. However, it has been possible to develop and maintain germ-free mouse lines, from whichall microorganisms have been removed58–61.The gut microbiota from conventional micecan then be transplanted into the germ-freemice (a process known as conventionaliza-tion) to assess how the recipients respondand in particular whether there are changesin obesity-related phenotypes, such aslipometabolism and inflammation.Using such an approach, the seminalpaper that indicated a putative causativerole for the gut microbiota in obesity39found that conventionalization of previouslylean and insulin-sensitive germ-free miceincreased their adiposity by 60% whilealso increasing their insulin resistance,despite the mice having a reduced foodintake. It was later shown that conventionali-zation of germ-free mice with the microbiotafrom obese mice led to substantially higheradiposity than conventionalization with themicrobiota from lean mice62,63. Althoughthese transplantation studies did not reportfully developed obesity in the recipientmice, they suggest that the gut microbiotahas the capacity to induce fat accumulationin the host.Another approach used to test the roleof the gut microbiota in the development ofobesity has been to investigate how germ-free animals respond to a high-caloric diet.The first study to use such an approachreported that germ-free mice are resistantto obesity induced by a high-fat, high-sugar ‘western’ diet, suggesting that the gutmicrobiota has a central role in the devel-opment of obesity in mice64. Indeed, evenafter 8 weeks on this diet, germ-free miceremained almost as lean as the control micefed on normal chow65,66. However, anotherreport showed that germ-free mice fed adifferent high-fat diet developed obesityafter 8 weeks, whereas mice fed the westerndiet did not67. In another recent study witha similar non-western high-fat diet, germ-free animals significantly increased theirbody weight in the first 8 weeks but thenstarted to lose weight, and after a further8 weeks their body weight was no differ-ent from the controls fed on normal chow,suggesting that if germ-free mice are kepton this high-fat diet for long enough, theyeventually became lean, despite a significantweight gain in the first few weeks56. Takentogether, these studies demonstrate that thewhole gut microbiota is an essential com-ponent in the development of diet-inducedobesity in mice, highlighting a potentialcausative role for the gut microbiota inhuman obesity.Creating pseudo-germ-free mice using anti-biotics. In many studies, pseudo-germ-freeanimals are created by removing most ofthe gut microbiota through treatment withcocktails of broad-spectrum antibiotics, suchas combinations containing cefadroxil, oxy-tetracycline and erythromycin68; neomycinsulphate and streptomycin69; ampicillin andneomycin70,71; and vancomycin, neomycinsulphate, metronidazole and ampicillin72–74.The ampicillin–neomycin cocktail eliminates~90% of the total gut bacteria71. Althoughindividual antibiotics can selectively sup-press particular bacterial populations, thecocktail containing vancomycin, neomycinsulphate, metronidazole and ampicillin cannon-preferentially deplete all bacteria thatare detectable with microbiological culturingtechniques72.Pseudo-germ-free animals provide anadditional approach to investigate the causa-tive role of the whole gut microbiota in thedevelopment of obesity70,71. The ampicillin–neomycin cocktail prevented the develop-ment of obesity in mice fed on a high-fatdiet, indicating that the gut microbiota isessential for this process70. This report ech-oes the previous finding that germ-free miceare resistant to obesity induced by a high-caloric diet64. Intriguingly, both leptin-defi-cient (ob/ob) mice and Toll-like receptor 5(TLR5)-knockout mice developed obesityand insulin resistance induced by hyperpha-gia (intake of excessive food)49,50. However,removal of most of the gut microbiota in P E R S P E C T I V E S640 | SEPTEMBER 2013 | VOLUME 11 /reviews/micro| MicrobiologyHealthTransitionDiseasethese mice using an ampicillin–neomycin cocktail alleviated inflammation, reduced food intake and prevented obesity and insu-lin resistance 70,71. These surprising findings show that the gut microbiota might even have an essential role in genetically induced hyperphagia and metabolic syndrome in mice. This suggests that although the gut microbiota is downstream of a high calorie intake or a genetic mutation, these organ-isms can still serve as an essential ‘check-point’ along the pathological pathway to obesity.Interestingly, a recent study found that subtherapeutic antibiotic therapy which altered the gut microbiota in young mice led to increased adiposity, which might explain the growth-promoting effects of the anti-biotics used as feed additives in agriculture, and also adds another piece of evidence that the gut microbiota has a causal effect in obesity 75.Evidence from human studies. Support for a causative role for the gut microbiota in the development of metabolic syndrome in humans was provided by a recent gut micro-biota transplantation trial 76. Using volunteers who received their own faecal microbiota as controls, the study showed that obese vol-unteers who receive a microbiota from lean donors have significantly improved insulin sensitivity in the serum (although not in the liver) over a 6-week period. This is the first time that the gut microbiota has been shown to have a causative role in the development of insulin resistance in humans.All these experimental manipulations of the gut microbiota have, in some way, followed the essence of Koch’s postulates in showing that the whole gut microbiota can work as a pathogen-like entity.Obesity-associated compositional patterns The question has now become whether we can identify specific members of the gut microbiota that are more relevant than others to the causative role of that microbiota in human obesity. If so, these members of the gut microbiota might serve as new targets for obesity control.Phylum- and class-level compositionalpatterns and obesity. Gordon and colleagues proposed the first obesity-associated compo-sitional pattern of the gut microbiota in their early seminal studies. They observed that the gut microbiotas of obese humans and obese (ob/ob ) mice had a significantly greater ratio of members of the phylum Firmicutes to members of the phylum Bacteroidetes (theF/B ratio) than their lean counterparts 63,77–80. The microbiota from obese individuals also had a lower bacterial diversity than that from lean individuals 62,79. Furthermore, when obese people lost weight using either a low-fat or a low-carbohydrate, calorie-restricted diet, the F/B ratio decreased in association with the percentage reduction in body weight (not caloric intake)78.This phylum-wide compositional pat-tern has also been reported in overweight pregnant women, in infants who became overweight later in childhood, in rats fed a high-fat diet, in genetically obese (fa /fa ) rats and following both diet- and bariatric surgery-induced weight loss 81–85. However, other studies in humans and rodents have reported no difference in the F/B ratio in obese versus lean individuals, no effect of weight loss on the F/B ratio, or even a reverse F/B ratio in obese individuals 38,39,86–91. The reason behind these contradictory obser-vations concerning the F/B ratio and obesity is unclear at present 92.Instead of the whole Firmicutes phylum being associated with obesity, the pres-ence of species from a predominant class within this phylum, Mollicutes (now called Erysipelotrichia), was substantially increased in western diet-fed obese mice, together with a concomitant reduction in other bacterial groups, including organisms from the phylum Bacteroidetes 62. This is the first indication that a diet-induced change in the gut microbiotamight not happen uniformly for each class-level taxon in the same phylum. We might need to go into deeper taxon levels to iden-tify changes in the gut microbiota that are associated with obesity.Species-level changes are more relevant to obesity. Within the class Mollicutes (Erysipelotrichia), the most predominant family in the human gut microbiota is Erysipelotrichaceae; four groups of closely related species-level phylotypes in this family were shown to be differentially responsive to changes in diet and metabolic phenotypes 38. The M1 group was predominant in healthy animals but reduced by one order of magni-tude in insulin-resistant mice, whether the insulin resistance was induced by genetic mutation or a high-fat diet. Perhaps more interestingly, the response to a high-fat diet was not uniform in this family. The M3 group dominated in mice fed on normal chow, whereas the M2 and M4 groups domi-nated in mice fed on a high-fat diet. Thus, closely related species-level phylotypes can respond to dietary changes in different ways, making it important to be careful when con-sidering patterns at higher-order taxonomic levels 38.Using longitudinal study designs to focus on species-level changes in the gut microbiota might also help us to identify members asso-ciated with obesity. The blooming of species from the class Mollicutes (Erysipelotrichia) inFigure 1 | Human health is influenced by interactions among the gut microbiota, the host and the environment. Humans are supraorganisms consisting of both human cells and microbial cells, particularly the gut microbiota. The gut microbiota interacts with host genetics and the environment (mainly diet) to influence the health of the human host. On the one hand, the gut microbiota releases toxins, such as lipopolysaccharides, and beneficial metabolites, such as vitamins and short-chain fatty acids, to damage or nourish humans, respectively. On the other hand, human genetics also imposes selective pressures on the gut microbiota through innate immunity or nutrient availability. The diet and particular drugs have a greater potential to shape the structure and function of the gut microbiota than host genetics, thus influencing the health state of the supraorganism.P E R S P E C T I V E SNATURE REVIEWS | MICROBIOLOGYVOLUME 11 | SEPTEMBER 2013 | 641diet-induced obese mice has been proposed to increase the energy harvest for the host, as demonstrated by the enrichment of genes involved in polysaccharide utilization inthe genome of a human-derived microbiota member in this class62. However, in a study on the structural resilience of the gut microbiota to high-fat feeding, a member of this class became predominant only after the mice had become obese, indicating that the blooming of some members in this class might be a consequence, rather than a cause, of obesity in the mice studies38.Several recent studies identified some key species-level phylotypes that are associated with obesity phenotypes in rodents39,71,93,94. For example, in one study, protective bacteria such as Bifidobacterium spp. were eliminated, whereas a species-level phylotype in the sul-phate-reducing family Desulfovibrionaceae was significantly enriched by 6 months of high-fat feeding38. Accumulating evidence indicates that LPS produced by Gram-negative opportunistic pathogens has an important role in the onset and progression of obesity in both rodents and humans, so below I focus on the potentially causative role of endotoxin producers in obesity.LPS-producing bacteria and obesityLPS is the major component of the outer membrane of Gram-negative bacteria and is an endotoxin that causes inflammation after entering the circulation95. The lipid A portion of LPS contains the endotoxin activity, but can have different levels of pro-inflammatory activity owing to variations in the detailed lipid A structure; LPS frommembers of the families Enterobacteriaceaeand Desulfovibrionaceae, in the phylumProteobacteria, exhibits an endotoxin activ-ity that is 1,000-fold that of LPS from thefamily Bacteroideaceae, in the phylumBacteroidetes (members of this phylum are themost numerous LPS producers in the gut)96.Obesity induced by purified LPS in mice.The aetiological role of gut-bacterial LPSin obesity was first well-characterized inmice55,70. Mice that were obese owing to ahigh-fat diet exhibited 2–3 times higherlevels of plasma LPS than non-obese mice(a threshold that is 10–50 times lower thanlevels observed during septicaemia or infec-tions) and also displayed low-grade systemicinflammation. Furthermore, injection ofEscherichia coli LPS subcutaneously for4 weeks into wild-type mice fed on normalchow led to the development of inflamma-tion, obesity, and fasted glycaemia and insu-linaemia55. Importantly, in CD14-knockoutmice, in which LPS cannot be recognized bythe innate immune system and thus cannotinduce inflammation, there was a delayed oreven complete lack of development of mostfeatures of metabolic diseases induced bya high-fat diet or LPS infusion55. Changesin the gut microbiota owing to antibiotictreatment reduced the LPS concentrationin both the caecal content and plasma,and also led to decreased inflammation,improved glucose intolerance and reducedobesity70. Thus, the low levels of LPS thatare derived from the gut bacteria have beenshown to cause obesity and insulin resist-ance in mice via an inflammation-dependentpathway, a phenomenon termed metabolicendotoxaemia55.Association of LPS-producing bacteriawith obesity. Families in the phylumProteobacteria (members of which arecommonly found in the human gut micro-biota96), such as Enterobacteriaceae andDesulfovibrionaceae, contain many patho-gens that can produce LPS as an endotoxin96.These LPS-producing bacteria are enrichedin obese humans and rodents. For example,Sprague Dawley rats with diet-inducedobesity exhibited higher concentrationsof plasma LPS and higher levels of gutEnterobacteriaceae members than rats thatremained lean on the same diet97. In obeseadolescent humans on an energy-restricteddiet (30–40%) and a physical exercise pro-gramme (with an energy expenditure of3,762–11,286 kJ per week) for 3 months,faecal Enterobacteriaceae members weresignificantly decreased in those individualswho showed remarkable weight loss(4–7 kg)98.In another study, Desulfovibrionaceaespecies were enriched in mice with highfat diet-induced obesity and insulin resist-ance compared with levels in lean mice fedon normal chow38. A cohort of 123 obesehuman volunteers (with a baseline bodymass index of ≥30 kg per m2) was placedon an intervention diet based on wholegrains, traditional Chinese medicinal foodsand prebiotics (the WTP diet) for 9 weeks.Improvement was observed in the levels ofinflammation, obesity and insulin resist-ance, and was associated with reducedlevels of proteobacteria, particularly thosefrom the families Enterobacteriaceae andDesulfovibrionaceae, in the gut (S. Xiao,N. Fei, X. Pang, L. Wang, B. Zhang, M. Zhang,X. Zhang, C. Zhang, M. Li, L. Sun, Z. Xue,J. Wang, J. Feng, F. Y an, N. Zhao, J. Liu,W. Long and L.Z., unpublished observations).It was recently reported that live Gram-negative bacteria can translocate from thegut into adipose tissue of high fat diet-fedmice, a phenomenon termed metabolicbacteraemia99. In a retrospective analysis ofblood samples from 3,280 human partici-pants, it was found that both controls andparticipants who developed diabetes shareda core blood microbiota that was mostlycomposed of proteobacteria (85–90%), butthe baseline 16S rRNA gene concentrationin the blood was higher in study participantswho developed diabetes after 9 years than inthose who did not100.P E R S P E C T I V E S642 | SEPTEMBER 2013 | VOLUME 11 /reviews/microTogether, these association studies indi-cate that LPS producers may be directly involved in inflammation-dependent adi-posity and insulin resistance in both rodents and humans.Host response to LPS-producing bacteria with obesity. After LPS in the gut enters the circulation, it is recognized and bound by LPS-binding protein (LBP), an acute-phase protein synthesized in the liver101,102. LBP then delivers LPS to CD14 and TLR4, which triggers the expression and productionof pro-inflammatory cytokines102,103. Pro-inflammatory cytokines, including tumour necrosis factor (TNF), interleukin-1(IL-1) and IL-6, induce serine phosphorylation of insulin receptor substrate 1 (IRS1) in muscle and adipose cells, and subsequently block insulin signalling in the peripheral tissues and induce insulin resistance104. Serum LBP and pro-inflammatory cytokines therefore link the immune response of the host to bloodstream LPS that is produced by bac-teria in the gut105. Epidemiological studies showed that obese individuals had higher plasma concentration of LPS, LBP and pro-inflammatory cytokines than lean individu-als105–108. Furthermore, in clinical studies, weight loss and improvement of insulin resistance were accompanied by a drop in the levels of serum LBP and inflammatory proteins56 (S. Xiao, N. Fei, X. Pang, L. Wang, B. Zhang, M. Zhang, X. Zhang, C. Zhang, M. Li, L. Sun, Z. Xue, J. Wang, J. Feng, F. Y an, N. Zhao, J. Liu, W. Long and L.Z., unpublished observations).In addition to low-grade inflammation, in which LPS might have a direct role, obese ani-mals also have an increased endocanna b inoid (eCB) level in the plasma and adipose tissues (that is, an increased eCB system tone), which is affected by the gut microbiota. The intesti-nal eCB system tone can in turn regulate gut permeability and plasma LPS levels, and LPS might control adipose tissue metabolism by blocking cannabinoid-driven adipogenesis109. LPS may thus have a pleiotropic role in regulating the development of obesity. Reproducing obesity with Enterobacter cloacae. If endotoxin producers have the potential to make a causative contribution to obesity development in humans, they should be isolated from the gut microbiota of obese human subjects and tested in an experimen-tal host to assess whether they do have the capacity to induce obesity. This reproduction of disease phenotypes in experimental hosts with pure isolates is in line with the evidence for causality required by Koch’s postulates.Recently, Enterobacter cloacae str. B29(referred to below as B29), which was iso-lated from the gut of an obese human, wasshown to cause obesity when introducedinto high fat diet-fed germ-free mice56.Enterobacter spp.-related bacteria constituted~35% of the gut microbiota of this individualbefore dietary intervention, but becameundetectable after the volunteer lost 51.4 kgof his 174.8 kg initial weight. In contrastto germ-free mice, which were essentiallyresistant to high fat diet-induced obesityand insulin resistance64, the B29-mono-associated gnotobiotic mice on a high-fatdiet became as obese and as insulin resistantas conventional mice fed with the samediet for the same time period56. B29-mono-associated mice on normal chow remainedlean, indicating that the high-fat diet actedas a cofactor with B29 in inducing obesity.In addition, the B29-mono-associated obesemice also exhibited a higher circulatingantigen load as reflected by serum LBP, andincreased inflammation in the circulation,liver and adipose tissues56. There was noincreased expression of inflammatory genesin the gut, indicating that the observedovergrowth of B29 might not be stimulatedby nitrate being released from the inflam-matory gut tissues and acting as an electronacceptor110. Gut barrier function might notbe affected either, as the expression levelsof genes encoding tight junction proteinswere not reduced in mice with B29-inducedobesity. The requirement for a high-fat dietin order for obesity to develop in B29-mono-associated mice might be due to the fact thatthese mice have an increased level of chylo-microns, which are used to absorb fat fromthe gut but have also been shown to takeLPS into the host111. Importantly, mono-association of a Bifidobacterium sp. straindid not overcome the resistance of germ-freemice to high fat diet-induced obesity, indi-cating that this obesity-inducing capacity isspecific to B29 (REF. 56).Notably, the B29-mono-associated obesemice also showed distorted expression offasting-induced adipose factor (Fiaf; alsoknown as Angptl4)56. When expressed inadipose tissues, liver and the intestine,FIAF can reduce the storage of fatty acidsin adipocytes by inhibiting the activityof a key enzyme called lipoprotein lipase(LPL). In addition to inhibiting fat stor-age, FIAF might also promote fat oxida-tion64,112. Previous work showed that Fiaf isconstitutively expressed in germ-free mice.Conventionalization of germ-free mice witha normal gut microbiota led to an increasein body fat in association with a decreasein Fiaf expression in the ileum, and a 122%increase in LPL activity in epididymal adi-pose tissue112. Furthermore, Fiaf-knockoutgerm-free mice were no longer resistant towestern diet-induced obesity64. Moreover,B29-mono-associated obese mice showedsignificantly reduced expression of Fiaf inthe ileum, whereas expression of the genesfor lipid synthesis in the liver, Acc1 (alsoknown as Acaca) and Fasn, was substantiallypromoted, as was also seen in germ-freemice that were conventionalized with thegut microbiota56,64.This is the first experimental demon-stration of a causative role of a specific gutbacterium in human obesity within the refer-ence framework of Koch’s postulates (BOX 2).In my opinion, the required combinationof high-fat diet and E. cloacae str. B29 forthe develop m ent of obesity might be com-parable to a latent infection, in which hostswho carry the pathogen might not developthe disease until the right environmentalconditions arise.Perspectives and future directionsChain of causation. Integration of the cur-rently available evidence from both humansand rodents supports the hypothesis thatlow-grade, systemic and chronic inflamma-tion induced by the gut microbiota can initi-ate and aggravate metabolic diseases suchas obesity and diabetes in humans. TakingE. cloacae str. B29 as an example, when thisendotoxin producer thrives in the gut ofan individual on a high-fat diet, it mightlead to an increased endotoxin load in thebloodstream, an increase in inflammatorycytokines and, eventually, the developmentof insulin resistance and excessive fat accu-mulation via disrupted regulation of hostlipometabolism56.However, many more questions remainto be answered, such as whether endotoxinproduction is the only ‘virulence factor’needed to induce obesity; whether the bac-teria produce a molecule (or molecules) todirectly regulate Fiaf or other host genes;how many other endotoxin-producingbacteria can also thrive in the gut of obesehumans and contribute to the disease;whether a Gram-positive opportunisticpathogen overgrowing in the gut of a patientwith obesity would also contribute to thedisease and, if so, how; and whether we canidentify key functional species that mighthave anti-obesity effects. In this last regard,short-chain fatty acid-producing bacteriamight be good candidates, as they have beenshown to have a role in regulating satiety,alleviating inflammation and protectingP E R S P E C T I V E SNATURE REVIEWS |MICROBIOLOGY VOLUME 11 | SEPTEMBER 2013 |643。

·研究论文·Chinese Journal of Animal Infectious Diseases中国动物传染病学报摘 要：为探寻一种更加合理高效的猪支原体肺炎（MPS ）免疫方式，本研究使用MPS 弱毒疫苗进行基础免疫后14 d 再使用灭活疫苗进行加强免疫，通过人工感染猪肺炎支原体来评价其免疫效果。

同时将这种免疫程序在规模化猪场进行应用，通过计算一定时期内的日增重来评价其免疫效果。

结果显示：联合免疫在保证黏膜免疫效果的同时并未降低体液免疫水平；更为重要的是，联合免疫不但具备较高攻毒保护率，而且在攻毒后剖杀时其肺泡灌洗液中抗原含量远低于其他免疫方式。

以上结果表明，联合免疫可以产生较好的免疫协同作用，从而提高了机体的综合免疫保护能力。

田间试验结果发现：联合免疫组猪群从21日龄至80日龄平均增重27.31 kg ，比活疫苗免疫组猪群多增重3.02 kg ，比灭活疫苗免疫组猪群多增重3.73 kg ；其平均日增重可达0.46 kg/d 。

本研究为防治猪支原体肺炎提供了新的思路。

关键词：猪支原体肺炎活疫苗和灭活疫苗；初免-加强免疫策略；攻毒保护；日增重中图分类号：S858.28文献标志码：A文章编号：1674-6422（2023）04-0089-07Evaluation of the Combined Vaccination Strategy of Attenuated and InactivatedVaccines against Mycoplasma hyopneumoniae Infection收稿日期：2021-03-01基金项目：江苏省农业科技自主创新资金项目（CX(20)1006）作者简介：郝飞，男，博士，助理研究员，主要从事动物支原体感染与黏膜免疫防控技术研究；白昀，男，硕士，副研究员，主要从事动物支原体感染与黏膜免疫防控技术研究通信作者：冯志新，E-mail:***************猪支原体肺炎活疫苗与灭活疫苗联合免疫效果评价郝 飞1,2，白 昀1,2，袁 厅1,2，张 磊1,2，刘蓓蓓1,2，谢 星1,2，韦艳娜1,2，甘 源1,2，熊祺琰1,2，邵国青1,2，冯志新1,2（1. 江苏省农业科学院兽医研究所 农业农村部兽用生物制品工程重点实验室，南京210014；2. 兽用生物制品（泰州）国泰技术创新中心，泰州 225300）2023,31(4):89-95Abstract: In order to explore a more reasonable and effi cient immunoprotection method for Mycoplasmal pneumonia of swine (MPS), a combined vaccination strategy was developed in the present study. Piglets were primed with the attenuated Mycoplasma hyopneumoniae (Mhp) vaccine and then boosted with the inactivated vaccine 14 days later. The vaccinated piglets were challenged with the virulent strain to evaluate the effi cacy of this combined vaccination method. At the same time, this immunization procedure was applied on the large-scale pig farms, and the effi cacy was evaluated by comparing the daily weight gain of piglets at different stages. The experiment result shows that the combined vaccination with the attenuated vaccine and inactivated vaccine did not reduce the humoral immunity level while ensuring the mucosal immunity effect. More importantly, the combined vaccination not only provided better protection but also reduced the Mhp antigen level in bronchoalveolar lavage fluid. These results indicated that the combination of Mhp attenuated vaccine with inactivated vaccine had good immune synergism and enhanced host immunoprotection. The fi eld experiment showed that the averageHAO Fei 1,2, BAI Yun 1,2, YUAN Ting 1,2, ZHANG Lei 1,2, LIU Beibei 1,2, XIE Xing 1,2, WEI Yanna 1,2,GAN Yuan 1,2, XIONG Qiyan 1,2, SHAO Guoqing 1,2, FENG Zhixin 1,2(1. Key Laboratory for Veterinary Bio-Product Engineering, Ministry of Agriculture and Rural Affairs,Institute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; 2. GuoTai (Taizhou) Center of Technology Innovation for VeterinaryBiologicals, Taizhou 225300, China)· 90 ·中国动物传染病学报2023年8月猪支原体肺炎（Mycoplasmal pneumonia of swine, MPS）又称猪气喘病或猪喘气病，是一种由猪肺炎支原体（Mycoplasma hyopneumoniae, Mhp）感染引起的以咳嗽、气喘、腹式呼吸和生长速度缓慢为主要特征的慢性呼吸道传染病。

Boost Your Immune SystemThe human immune system is nothing short of amazing. It’s so complex and sophisticated that we only now know a very small fraction, say 1-2%, of how it all works. What we do know, is that the strength of our immune system determines the state of our health.When our immune system is strong and functioning properly, we tend to be healthy. When our immune system becomes compromised, we begin to become susceptible to unwanted illnesses- colds, flu, and other infections.Your Incredible Immune SystemThe immune system is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites that would love to invade your body.When you get a cut, all sorts of bacteria and viruses enter your body through the break in the skin. Your immune system responds and eliminates the invaders while the skin heals itself and seals the puncture. In some cases the immune system misses something and the cut gets infected. It gets inflamed and will often fill with a whitish-yellow, yellow or yellow-brown substance commonly known as pus. Pus consists of a thin, protein-rich fluid and dead cells, which are part of the body's innate immune response.Each day you inhale thousands of germs (bacteria and viruses) that are floating in the air. Your immune system deals with all of them without a problem. Occasionally a germ gets past the immune system and you catch a cold, get the flu or worse. A cold or flu is a visible sign that your immune system failed to stop the germ. The fact that you get over the cold, or flu is a visible sign that your immune system was working properly to eliminate the foreign invader.Each day you also eat hundreds of germs, and again most of these die in the saliva or the acid of the stomach. Occasionally, however, one gets through and causes food poisoning. There is normally a very visible effect of this breach of the immune system: vomiting and diarrhea are two of the most common symptoms of a compromised immune system.The immune system has special cells known as white blood cells (WBC) that patrol the body for invading organisms. Proteins in the form of antibodies help us identify and resist repeated infections. In addition to the circulatory system that regulates our blood flow, we also have a separate circulatory system for the immune cells, known as the lymph system.The lymph system is made up of water, dissolved proteins, and other waste fluids (toxins) that leak through the capillaries into the spaces between the body tissues. This fluid called lymph, is collected and rerouted through the body’s lymph nodes. The lymph nodes are small pea like structures that contain a large number of immune cells. The nodes are distributed throughout the body.Lymph nodes can be found in the armpits, groin, behind the ears, as well as the thorax and abdomen. Lymph nodes may become enlarged when our bodies are fighting off an infection. Those with CFS may have chronic inflamed and enlarged nodes that can be felt in the armpits or along the throat just below the chin.Disease producing microorganisms (pathogens) are ever present in our environment. These pathogens are in the air we breathe, the food we eat, and surfaces we are exposed to. In fact, if our skin, throat, or other mucous membranes were cultured, most all of us would be found to contain one type of pathogen or another. For example, at any given time of the year 5-40% of us have pneumococcus bacteria in our nose and throat, yet we rarely develop pneumonia because our immune system keeps these pathogens under control.The question is often asked why does one person comes down with the flu and their co-worker or family member doesn’t? Although there are many factors that may affect who gets sick and who doesn’t, the strength of our immune system ultimately determines our fate.It’s not the seed (germ) that determines who gets sick, but the soil (state of the immune system) that the seed is planted into.Non-specific and Specific ImmunityWhen a foreign invader enters the body or a cell becomes cancerous, the immune system handles it with two types of defenses.A.Non-specific defenses are called cell mediated immunity. Cell mediatedimmunity involves special white cells (typically T cell lymphocytes andNeutrophils) which immediately organizes an attack against the invadingpathogen. Cell mediated immunity attempts to either prevent the invader fromentering the body, or quickly destroy it once it does enter the body. Cell mediated immunity is best suited to helping the body resist infection by yeast, fungi,parasites, and viruses, including those associated with CFS, herpes simplex,Epstein-Barr and cytomegalovirus. Cell mediated immunity is also critical inprotecting against the development of cancer and is commonly involved inallergic reactions.B. Specific defenses are known as humoral immunity. Humoral immunity relies on special molecules including white blood cells and antibodies. These special molecules are present in body fluids.The humoral immunity forms antibodies to match the surface cells of foreign invaders.It may take several days before these antibodies can be produced and delivered to the offending microorganisms.T-CellsImmune cells originate in the bone marrow. About half of the immune cells are transported to the thymus gland. The thymus gland is located just underneath the breast bone and is the size of a walnut. The thymus gland is the source of powerful hormonesthat transform the newly formed cells into mature T-cells. T-cells patrol every part of the body for foreign invaders. These specialized cells help prevent cancer by destroying abnormal cells before they can proliferate.T-Cells make-up the majority of the cell-mediated immune system.There are many different kinds of T-cells. The most important ones are the following: Helper T-Cells – enhance the action of the other T-cells. They sound the alarm Suppressor T-Cells – dampen or turn down the immune system. They signal all is clear. Killer T-Cells – destroy invaders, including viral and cancerous cells.B-CellsThe other type of lymphocyte that plays a major role in the immune response is the B-cell. The B-cell is an agent of the fast acting humoral immune system. The B-cell helps manufacture antibodies (immunoglobulins). The antibodies are released by the B-cells into the blood steam and are then carried to the specific site of infection.Antibodies can perform in various ways. Some neutralize the poisons produced from bacteria. Others coat the bacteria and allow phagocytes or scavenger cells to engulf and digest the bacteria.Other immune cells known as macrophages, are large scavengers that help clean up any left over debris.One of the most important of the null cells is the Natural Killer Cell (NK cell). NK cells are especially important for those with CFS. These cells seek out and destroy virally infected cells. The Defense SystemThe first line of defense is the surfaces of the body which works to prevent pathogens from entering. This line of defense is composed of three parts: mucous, antibodies, and the cells themselves.Mucous is a sticky substance that’s found within the body includ ing the respiratory tract. It traps the pathogens and moves them off the membranes out of the nose or into the intestines where they are destroyed by the stomach acid.Secretory IgA is an important immunoglobulin that releases chemicals that bind to the pathogens. This reaction then blocks the penetration of the mucous membranes.Finally, the mucous membranes themselves form mechanical barriers to the invader. Once a pathogen gets past the surface defenses, it invades the tissues, begins to spread, and causes the cells to become damaged.When this happens, the cells secrete a wide range of special chemicals including histamine, bradykinins and serotonin. These chemicals alert the immune system that the body is under attack and trigger an increase blood supply to the area (this is why someone gets inflammation and has a fever).Now the non-specific immune response, the cell mediated defense team, is activated. Various classes of white cells, especially neutrophils, migrate to the area, and attack the invaders. As a pathogen is damaged by the white cells, parts of the pathogen leak out of the cell. These foreign parts or antigens activate the specific immune response, the humoral defense team. The antigens come in contact with special white cells called B lymphocytes, which then produce specific antibodies that are antagonistic to the invader. These antibodies directly attack the invaders and make them more recognizable by the powerful macrophages (which are like Pac-men) which also attack invading pathogens.Immune System ZappersDr. Joseph Pizzorno, in his book “Total Wellness Improve Your Health By Understanding The Body’s Healing Systems” lists the following immune zappers: Sugar and other simple carbohydrates. One tablespoon of sugar in any form, sucrose, honey, or fruit juice results in a 50% reduction in white blood cell activity for up to 5 hours.Alcohol- can reduce the amount and activity of white blood cells.Food allergies- cause the immune system to “ramp-up” and become over sti mulated. Food allergies damage the intestines (Leaky Gut) allowing immune-damaging toxins to enter the body. Chronic immune challenges from food allergies may overwhelm secretory IgA reserves.Hypothyroid- can reduce the speed and effectiveness of enzymes associated with supporting immune functions.Adrenal Dysfunction- causes lowered resistance to all forms of stress leading to lowered immune resistance.Chronic Stress-eventually leads to adrenal exhaustion.Being Overweight-causes a reduction in bacterial killing white blood cells.Heavy Metals- including cadmium, lead and mercury inhibit the formation of antibodies, and reduce the bacteria-killing ability of white blood cells.Pesticides and other Environmental Toxins-can overwhelm the immune system and its supporting cast (liver, kidneys, etc.). Pesticides depress T and B lymphocytes and place a drain on the lymph system, especially the thymus gland.Drugs- including acetaminophen, aspirin, Ibuprofen, and corticosteroids decrease antibody production.Inadequate Rest- suppresses natural killer cell activity.Candida Overgrowth-may allow toxins to be released directly into the body. These toxins cause the immune system to become overwhelmed and can initiate a host of immune disrupting symptoms.Severe Trauma including Accidents, Surgeries and Burns- are extremely stressful to the body as a whole. Traumas can cause vitamin, mineral and other essential nutrients to become deficient. Inflammatory responses overloads the immune system.Chronic Antibiotic Use. General immune impairment increases overgrowth of candida, makes bacteria stronger and more resistant to immune system.Supplements that Boost the Immune SystemThymus ExtractsA substantial amount of clinical data now supports the effectiveness of using thymus extracts. Thymus extracts may provide the answer to chronic viral infections and low immune function. Double-blind studies reveal not only that orally administrated thymus extracts were able to effectively eliminate infection, but also that treatment over the course of a year significantly reduced the number of respiratory infections and significantly improved numerous immune parameters.The thymus gland is located at the base of the neck, right below the thyroid and above the heart. It is considered the master gland of the immune system. It is especially susceptible to free radicals, stress, infection, chronic illness, and radiation. When overly stressed it begins to shrink.The thymus is involved in producing T cells and are in charge of cell mediated immunity. T cells assist the immune system without need for antibodies. These cells help fight against bacteria, fungi, parasites, and yeast. The production of T cells by the thymus creates resistance to many viruses including herpes simplex, Epstein-Barr, and the viruses associated with hepatitis.Thymus glandular extracts (like other glandular extracts) are able to raise T-cells when needed but will lower T-cells when an autoimmune disease is present. This balancing act is the big advantage glandular extracts, and many natural herbs have over prescription (synthetic) drugs.Thymus Glandular Extracts can found at some health food stores, or by calling my clinic.Zinc is an important cofactor in the manufacture, secretion, and function of thymus hormones. When the zinc levels are low, T cell numbers go down. This may explain why zinc lozenges, when used at the first sign of a cold, can reduce the number of sick days.A good multivitamin/mineral formula can provide antioxidants that will help protect the thymus gland from free radical damage. Vitamins A, C, and E along with the minerals zinc and selenium play a vital role in reducing the damage associated with free radical toxicity.Selenium. One study on selenium, 200 mcg a day, to individuals with normal selenium concentrated in their blood resulted in a 118% increase in ability of lymphocytes to kill tumor cells, and an 82.3% of increase in the activity in natural killer cells.A good multivitamin/mineral formula with zinc, selenium, vitamins A, C, andB vitamins is a smart and potent way to boost immune function.Herbal Immune Boosting SupplementsAstragalus membranaceus.Research in animals has shown that Astragalus apparently works by stimulating several factors of the immune system, including enhancing phagocytic activity of monocytes andmacrophages, increasing interferon production in natural killer cell activity, enhancing T-cell activity, and potentiating other anti-viral mechanisms.Echinacea (Purple coneflower)Echinacea is one of the most popular herbal medicines in the United States and Europe. In 1994, German physicians prescribed Echinacea more than 2.5 million times.There are over 200 journal articles written about Echinacea.Echinacea is thought to stimulate the immune system by increasing the production of and activity of white blood cells, especially natural killer cells (NK cells).Goldenseal is a perennial herb native to eastern North America. This herb has shown to be a potent immune stimulator.It increases the blood flow to the spleen and increases the number and activity of macrophages. Macrophages are released in response to foreign substances that invade the body.These white blood cells roam around the body destroying unwanted bacteria, viruses, yeast, and tumor cells.Elderberry- In 1992, a team of Israeli scientists headed by Madeleine Mumcuoglu (pronounced Mum-shoe-glue) set out to study the effect of elderberry on flu patients. During a flu epidemic at an Israeli Kibbutz, half of the flu patients were given an elderberry syrup, the other half a placebo.The results: within 24 hours, 20% of the patients receiving elderberry had gotten significantly better.Within two days, 75% of the elderberry group was much improved; within 3 days 90% were completely cured. Among the placebo group, only 8% of patients improved within 24 hours and it was a full 6 days before 90% of the patients were cured.Flu viruses invade cells by puncturing the cell walls with little spikes called hemagglutinin. These spikes are coated with an enzyme called neuraminidase, which helps break down the cell walls. Elderberry appears to actually disarm these spikes and inhibit the action of this enzyme- thus preventing flu viruses from invading cells. Licorice RootThis herb has long been valued as a demulcent (soothing, coating agent) and continues to be used by professional herbalists today to relieve respiratory ailments (such as allergies, bronchitis, colds, sore throats, and tuberculosis), stomach problems (including, possibly, heartburn from reflux or some other cause and gastritis), inflammatory disorders, skin diseases, and liver problems.I recommend my patients use a combination of all of these potent immune boosting supplements.All of the above immune boosting herbal supplements, are contained in Essential Therapeutics Viral Formula which can be ordered by calling the clinic.。