1、胃肠道黏膜先天性免疫应答刘占举 M.D.,Ph.D郑州大学第二附属医院消化内科 Innate Immunity in gut mucosa 介绍胃肠道先天性免疫防御机制。了解胃肠道先天免疫系统如何识别肠道病原微生物。病原体识别信号系统。病原微生物感染引起肠道黏膜炎症应答。Lecture aims 消化道是外界抗原或病原微生物进入体内的门户。有生理性和生物学屏障阻挡着这些抗原的侵入，并保持着肠道粘膜组织“内环境”的稳定。1年内有30 kg食物蛋白通过肠道；每天有130190g抗原被吸收进入机体。每克粪便1012个微生物，这些微生物抗原可通过肠道粘膜吸收进入机体引起免疫反应。消化道也是免疫器官，有
2、许多免疫细胞参与了肠道粘膜免疫应答。当食物或细菌抗原接触胃肠道后，抗原成分被肠粘膜Peyers patches表面的M细胞吸收，引起一系列的免疫反应，出现免疫耐受，即对食物抗原不应答；否则引起食物过敏反应或炎症应答。Gastric mucosal protective factors病原微生物进入体内后 识别 免疫应答（先天性、获得性）清除 免疫病理（过敏、感染、炎症）Pathogenic infectionImmune responseInnate immunity(non specific)先天性与获得性免疫应答Adaptive immunity(Ag specific)Inflammat
3、ionMemory of infection获得性免疫应答：Ag特异性防御机制，抗原刺激数天后形成免疫保护，以排除体内特异性抗原。终生伴随。先天性免疫应答：Ag非特异性防御机制，遇到任何抗原后迅速或数小时后形成，以清除病原体，是机体先天固有的。先天性免疫组成先天性免疫组成 -生理性屏障 -补体系统 -细胞组成 -细胞因子、炎症反应病原体识别病原体识别 -Pathogen-associated molecular patterns(PAMPs)-Pattern recognition receptors(PRRs)-Toll-like receptors(TLR)-NF-kB activatio
4、n -TLR signaling -Nod proteins病原识别及炎症反应异常引起的疾病病原识别及炎症反应异常引起的疾病 -Nod and Crohns disease -Celiac disease -Bacterial infection先天性免疫应答Cells types involved in innate immunityNeutrophilsMonocytes/MacrophagesNK cellsDendritic cellsFunctionsKilling by PhagocytosisReactive oxygen speciesAntimicrobial peptide
5、sExtracellular trapsKilling by PhagocytosisInflammation mediatorsReactive oxygen speciesComplt proteinsAg presentationAg presentationCostimulatory signalsCytokinesLysis of viral infected cellsActivation of macrophagesMast cellsPromote inflammation by releasingHistamineLeukotriensProstaglandinCellsIn
6、nate immunity:cytokines细胞因子是免疫细胞遇到抗原刺激后分泌的小分子可溶性蛋白，是调节先天性和获得性免疫应答的化学信使。调节先天性免疫应答的细胞因子：Monocytes Macrophages Dendritic cells TNF-a IL-1 Chemokines(ex:IL-8)Sequential steps of Pathogen eliminationPlasmaNormal capillaryEndothelial cellsNo injury or infectionMast cellsNeutrophilsMonocytesT and B Lymphoc
7、ytesEosinophilsBasophilsResident MacrophagesPlasmaNormal capillaryMast cellsNeutrophilsMonocytesT and B LymphocytesEosinophilsBasophilsComplement,Bacterial peptides fMet-Leu-Phe(fMLP)PlasmaNormal capillaryNeutrophilsMonocytesT and B LymphocytesEosinophilsBasophilsChemotaxisPathogen recognitionPhagoc
8、ytosis and cytokinesInflammationPlasmaNormal capillaryNeutrophilsMonocytesT and B LymphocytesEosinophilsBasophilsChemotaxisPathogen recognitionPhagocytosis and cytokinesInflammationSequential steps of Pathogen eliminationMediators of inflammation(Histamine,cytokines,chemokines)Dilating capillary dur
9、ing inflammationNeutrophilsMonocytesLymphocytesEosinophilsComplementClotting factorsAbKilling mechanismsMACMembrane attack complexPhagocytosis白细胞向血管腔外迁徙Cell 2000Inflammation:transmigration of neutrophilsE-selectinP-SelectinICAM-1问题：先天性免疫系统如何识 别病原微生物抗原？先天性快速（小时内）慢（3-5天）细胞表面特异性识别受体受体特异性识别抗原决定簇吞噬细胞（中性粒
10、细胞、巨噬细胞）炎症介质（噬碱性粒细胞、肥大细 胞、噬酸性粒细胞）NK细胞补体细胞因子APC（巨噬细胞、DC）Ag特异性B细胞Ag特异性T细胞Ab、CTL、细胞因子大多抗原决定簇来自病原体的多肽BCR、TCR识别抗原?获得性先天性免疫系统对病原体的识别系统Pathogen-associated molecular patterns(PAMPs，病原相关分子模式)Pattern recognition receptors(PRRs，模式识别受体)Toll-like receptors(TLR)NF-KB activationTLR signalingNod proteins病原相关的分子模式：P
11、AMP模式识别受体：PRRPathogen-Associated Molecular Patterns(PAMPS)Pathogen Recognition Receptor(PRR)MacrophagePAMPs主要特点：微生物(非机体细胞)产生，以确保先天免疫系统识别自身和非自身抗原。PAMP是微生物生存所必需的。PAMP是很稳定的，仅有限的PRR可以识别之。PAMPS:G-菌的LPSG+（少部分G-）菌细胞壁肽糖类抗原G+菌细胞壁磷脂壁酸、微生物糖蛋白、糖脂质蛋白细菌鞭毛蛋白flagellin菌毛蛋白pilin细菌和病毒的核酸物质 细菌的N-甲酰蛋氨酸dsRNA 霉菌的糖脂蛋白微生物膜表
12、面的磷脂酰胆碱PAMP组成组成PAMPS:Pattern Recognition ReceptorsToll-like receptors(TLRs):1.I型转膜蛋白2.首先在黑腹果蝇中发现3.后来在哺乳类动物、鱼、鸡、植物中发现，可能来自一个起源。4.命名来自黑腹果蝇的基因Toll。5.1996年，发现Toll是苍蝇识别真菌感染基因。6.1997年发现Toll表达在哺乳类细胞。Leucine-rich repeats(LRRs)Toll/IL-1 Rc domain(TIR domain)Pattern Recognition Receptors(PRRs)：TLR2 classes of
13、 PRRs:-Endocytic PRRs -Signaling PRRsPRRsEndocytic PRRs:在吞噬细胞表面，促使细胞对病原微生物 的吞噬。Signaling PRRs:与微生物结合，促使细胞因子分泌，引起 先天性和获得性免疫应答。TLR识别微生物抗原成分TLR分布(Viral)Uracil-rich single-stranded viral RNA(ex:HIV)Unmethylated cytosine-guanine dinucleotide sequences(CpG DNA)found in bacterial and viral genomes细胞膜 TLR信号
14、传导信号传导Pathogen-Associated Molecular Patterns(PAMPS)Pathogen Recognition Receptor(PRR)MacrophageUp regulation of cytokine genes InflammationNucleusTLR activationAdaptor proteinsNF-KB activation(Transcription factor)InflammationTLR信号诱导信号诱导NF-KB激活激活Toll-like receptorLeucine-rich repeats(LRRs)Toll/IL-1
15、Rc domain(TIR domain)Adaptor protein:MyD88Toll/IL-1 Rc domain(TIR domain)Death domainDeath domainIRAK:IL-1 associated kinaseNucleusNF-kBTRAF6IKKsPathogen recognitionTLR activationTLR信号传导信号传导TLR在免疫细胞表面表达在免疫细胞表面表达先天性免疫与获得性免疫联系 表达TLR 通过TLR识别PAMP(除隐窝上皮)Nod蛋白Commensal bacteria:肠道营养必需菌 促使肠道发育 阻止肠道病原微生物的感染
16、Mucosal epithelium:Intestine and commensal bacteriaIntestinal crypt肠腔内抗原进入体内的途径NF-KBNodShigellaInflammationDisruption of epithelium integrity GM-CSFCXCL1CYR-61IL-8ICAM-1微生物抗原诱导上皮细胞Nod激活、促使炎症应答NeutrophilsNod蛋白:表达的IEC、Mf Nod1（Card4）、Nod2（Card15）细胞内识别细菌抗原Nod分子分子Caspase-activating and recruitment domain
17、Leucine-rich repeatNucleotide binding siteMicrobial motif sensingOligomerization necessary for signal transductionHomophilic interactions with other proteins containing these domains(apoptosis/inflammation)Nod1和Nod2识别细菌肽糖类抗原Gram-Gram+Nod诱导NF-kB激活Nod:Nucleotide-binding oligomerization domainRICK:RIP-
18、like CARD-containing domainInflammationRussel RK.et al.,ADC online,2004;89;598-603病原微生物识别异常导致炎症疾病发生Nod and Crohns disease：Mutant Nod2 is a predisposing risk factor for CD,which is likely to act in synergy with other factors both genetic and environmental,in causing the disease.NOD2突变与Crohns disease
19、NBSRegion involved in peptidoglycan recognitionHeterozygous carriers:2 to 4-fold increased riskHomozygous carriers:15 to 40-fold increased riskLoss of functionFailure in NF-KB activationCrohns disease?肠道菌群改变导致的免疫激活异常 使细胞凋亡机制失常 导致CD慢性炎症和组织破坏 与CD临床类型有关（纤维化、狭窄）NOD2突变与Crohns disease PeptidoglycanMuramyl dipeptide=MDPNormal NOD2NOD2 variantCD患者NOD2突变IFNg gEckmann L.et al,Immunity 2005；22;661总结先天性免疫应答是机体本身固有的，识别病原微生物的侵袭，清除感染。肠道黏膜上皮细TLR、Nod对PAMP的识别，引起肠道黏膜的免疫保护。先天性免疫应答异常（Nod基因突变），引起肠道炎症性疾病（Crohns disease)。谢 谢刘占举450014 郑州市经八路2号郑州大学第二附属医院消化内科Email:Cell phone:13598826127
