1、黏膜免疫Mucosal Immune黏膜免疫系統與免疫應答黏膜免疫系統中的固有免疫應答黏膜免疫系統中的適應性免疫應答黏膜免疫中的免疫耐受和免疫調節粘膜免疫與疾病The mucosal immune system. The tissues of the mucosal immune system are the lymphoid organs associated with the intestine, respiratory tract, and urogenital tract, as well as the oral cavity and pharynx and the glands as

2、sociated with these tissues, such as the salivary glands and lachrymal glands. The lactating breast is also part of the mucosal immune system. 直接接觸病原體的解剖部位并能夠分泌粘液的上皮細胞所覆蓋，構成粘膜免疫系統（mucosal immune system）。包括啟動和行使免疫應答的粘膜下固有層中各種散在的免疫細胞和一些器官化的淋巴組織，還包括與此相關的多種內分泌腺體：胰腺、眼結膜和淚腺、唾液腺以及乳腺。因而黏膜免疫系統亦稱黏膜相關淋巴組織（muco

3、sa-associated lymphoid tissue, MALT）。一、黏膜免疫系統的結構特點二、黏膜免疫系統的應答特點黏膜免疫系統與免疫應答黏膜免疫系統的結構特點Cross-sectional diagram of the mucous membrane lining the intestine showing a nodule of lymphoid follicles that constitutes a Peyers patch in the submucosa. The intestinal lamina propria contains loose clusters of l

4、ymphoid cells and diffuse follicles.小腸黏膜免疫系統的各種細胞成分和器官化的淋巴組織 腸腔固有層腸系膜粘膜上皮DCM細胞小腸上皮細胞 上皮內淋巴細胞 (IEL)絨毛共生菌粘液漿細胞隱窩杯狀細胞IgA巨噬細胞腸腺嗜酸細胞B細胞T細胞抗菌肽DC輸出淋巴管肥大細胞分立的 淋巴濾泡 派氏集合淋巴結濾泡T細胞腸系膜淋巴結粘膜免疫系統的特點 解剖特征 粘膜上皮和淋巴組織間因相互作用而聯系緊密。 由散在的淋巴組織和器官化的結構（如派氏集合淋巴結、 分立的淋巴濾泡和扁桃體）共同組成。 啟用特化的抗原攝取機制，如出現派氏集合淋巴結和M細胞。 效應機制 在無感染發生的情況下擁有

5、大量活化的T細胞和記憶細胞。 存在非特異性激活的“天然”效應性T細胞和記憶性T細胞。 大量啟用分泌型IgA抗體。 涉及各種共生微生物菌叢。 免疫調節 可主動下調針對食物和其它共生性抗原的強勢免疫應答。 可激活抑制性巨噬細胞及誘導耐受的樹突狀細胞。一、組成腸相關淋巴組織的固有免疫細胞二、腸道粘膜相關的固有免疫應答 三、上皮內淋巴細胞殺傷入侵病毒和修復損傷組織黏膜免疫中的固有免疫應答The lamina propria and epithelium of the intestinal mucosa are discrete lymphoid compartments. The lamina pro

6、pria contains a heterogeneous mixture of lgA-producing plasma cells, lymphocytes with a memory phenotype , conventional CD4 and CD8 effector T cells, dendritic cells, macrophages, and mast cells. T cells in the lamina propria of the small intestine express the integrin 4:7 and the chemokine receptor

7、 CCR9, which attracts them into the tissue from the bloodstream. lntraepithelial lymphocytes express CCR9 and the integrin E:7, which binds to E-cadherin on epithelial cells. They are mostly CD8 T cells, some of which express the conventional a:B form of CD8 and others the CD8a:a homodimer. CD4 T ce

8、lls predominate in the lamina propria, whereas CD8 T cells predominate in the epithelium.組成腸相關淋巴組織的固有免疫細胞 粘膜淋巴細胞及其與上皮細胞相互作用的分子機制圖中所示粘膜淋巴細胞主要指位于粘膜上皮細胞間和上皮細胞基底層一側的T 淋巴細胞，包括固有類T 淋巴細胞和NK細胞。此類細胞不僅分布部位特殊，而且功能發揮皆受控于上皮細胞表面各類MHC分子與其受體分子間的相互作用。有意義的是，除了經典的MHC I 類和II 類分子，上皮細胞還表達范圍廣泛的各種非經典MHC分子，包括TL、HLA-E、MIC-A/

9、-B、MR1和進化上與之高度同源的CD1d 分子，激活多種粘膜淋巴細胞。 TL MHC II MHC I TL MIC- MIC - HLA-E CD1d/ MR1 A/-B A/-B -GalCel CD8 CD4 CD8 CD8 NKG2D CD94/ TCR TCR TCR TCR TCR NKG2ATCR TCR TCR TCR NK NKT MAITCD8 CD4 T CD8 T CD8 TGF- IFN-,IL-4 Pf,Gz,FasL IL-6, KGF TNF-, Pf, Gz, IFN-,IL-4 ? TNF- IFN- FasL 調節 Th1/Th2 毒性 炎癥, 修復，

10、炎癥 毒性 Th1/Th2 ？ 功能 毒性 抗炎 功能？BCRB受體上皮細胞配體粘膜淋巴細胞分泌因子功能 TL: 非經典MHC I 類分子 胸腺白血病抗原；MIC: MHC I 類鏈相關分子；CD1d/a-GalCel: 分化抗原CD1d分子提呈的 半乳糖神經 酰胺； MR1: MHC相關I 類分子；MAIT: MR1限制性粘膜相關恒定鏈T 細胞; Pf: 穿孔素；Gz: 顆粒酶。KGF: 角朊細胞生長因子。 腸道上皮細胞的免疫屏障功能腸道上皮細胞分泌的粘液防止微生物接近上皮細胞腸道上皮細胞產生的防御素和細胞因子具有抗菌活性腸道上皮細胞表達的TLR和NLR顯示雙重免疫功能固有層中的DC和巨噬細

11、胞具有炎癥反應抑制作用和免疫調節作用腸道粘膜相關的固有免疫應答Many barriers prevent pathogens from crossing epithelia and colonizing tissues. Surface epithelia provide mechanical, chemical, and microbiological barriers to infection.小腸黏膜中固有免疫應答的調控機制小腸上皮細胞及固有層中DC上PRR的表達和功能可降低針對腸腔共生微生物的炎癥反應。上端：能識別細菌鞭毛的PRR僅作為NLR表達于胞質中和作為TLR表達于小腸上皮細胞基

12、底膜一側，因而PRR對共生微生物的炎癥反應只有當微生物進入或穿越上皮細胞后才能產生。右下端：識別LPS的TLR4在小腸上皮細胞及固有層DC上的表達皆下調。而且固有層DC中TLR信號并不誘導炎癥基因的表達，因為其中能下調TLR信號轉導的胞內調節蛋白可優勢表達。TLRTLR4 DCNLR 細菌PAMP小腸上皮層固有層Epithelial cells have a crucial role in innate defense against pathogens. TLRs are present in intracellular vesicles or on the basolateral or a

13、pical surfaces of epithelial cells, where they recognize different components of invading bacteria. NOD1 and NOD2 pattern-recognition receptors are found in the cytoplasm and recognize cellwall peptides from bacteria. Both TLRs and NODs activate the NFB pathway leading to the generation of pro-infla

14、mmatory responses by epithelial cells. These include the production of chemokines such as CXCL8, CXCL 1 (GROa), CCL 1, and CCL2, which attract neutrophils and macrophages, and CCL20 and -defensin, which attract immature dendritic cells in addition to possessing antimicrobial properties. The cytokine

15、s IL-1 and IL-6 are also produced and activate macrophages and other components of the acute inflammatory response. The epithelial cells also express MIC-A and MIC-B and other stress-related nonclassical MHC molecules, which can be recognized by cells of the innate immune system. IB, inhibitor of NF

16、B.Commensal bacteria can prevent inflammatory responses in the intestine. The pro-inflammatory transcription factor NFB pathwayis activated in epithelial cells via the ligation of TLRs by pathogens (first two panels). Commensal bacteria have been found to inhibit this pathway and thus prevent inflam

17、mation. One way is by activation of the nuclear receptor PPAR, leading to the export of NFB fromthe nucleus (third panel). Another is by blocking the degradation of the inhibitor IB and thus retaining NFB in the cytoplasm (fourth panel).IEL參與構筑粘膜防御屏障IEL對病原體的殺傷功能IEL的維穩和保護功能的功能IEL殺傷入侵病毒和修復損傷組織病毒 食物抗原

18、（谷朊肽）TCR MHC I類分子 MIC-A/-B NKG2D LT CD8 CD8 Fas FasL Gz (顆粒酶) Pf (穿孔素) a型和b型粘膜上皮細胞間淋巴細胞（IEL）的主要功能A. a型IEL。左：病毒感染粘膜上皮細胞；中：受感染細胞通過MHC I類分子向CD8 IEL展示病毒抗原肽，激活IEL；右：激活的IEL行使典型的CTL功能，通過分泌Pf和Gz，以及通過Fas/FasL途徑殺傷病毒感染的上皮細胞；B. b型IEL。左：發生應急改變（感染、損傷、接觸毒性肽）的上皮細胞表達非經典MHC分子MIC-A、MIC-B和胸腺白血病抗原 (LT) ；中：IEL表達NKG2D和CD8

19、分子，分別與MIC-A/-B以及LT結合，IEL被激活；右：激活的IEL殺傷受到應急損傷的上皮細胞，機制同上 。上皮細胞CD8 IELABa型IELb型IEL一、黏膜免疫系統器官化的淋巴組織二、參與適應性黏膜免疫應答的免疫細胞三、黏膜免疫中的抗體應答四、黏膜免疫中T細胞介導的應答黏膜免疫系統中的適應性免疫應答黏膜免疫系統器官化的淋巴組織派氏集合淋巴結與M細胞散在性淋巴濾泡腸系膜淋巴結Uptake and transport of antigens by M cells. The first three panels show uptake via M cells in the follicle

20、-associated epithelium of Peyers patches. These have convoluted basal membranes that form pockets within the epithelial layer, allowing close contact with lymphocytes and other cells. This favors the local transport of antigens that have been taken up from the intestine by the M cells and their deli

21、very to dendritic cells for antigen presentation. The micrograph of part of a Peyers patch on the right shows epithelial cells (dark blue), some of which are M cells that form pockets where T cells (red) and B cells (green) accumulate. The cells have been stained with fluorescently labeled antibodie

22、s specific for individual cell types. Micrograph from Brandtzaeg, P., eta/.: lmmunol. Today 1999, 20:141-151.黏膜免疫系統含有大量效應淋巴細胞黏膜免疫系統中獨特的樹突狀細胞黏膜固有層中T細胞的致敏和歸巢參與適應性黏膜免疫應答的免疫細胞Capture of antigens from the intestinal lumen by mononuclear cells in the lamina propria. First panel: soluble antigens such as f

23、ood proteins might be transported directly across or between enterocytes, or there might be M cells in the surface epithelium outside Peyers patches. Second panel: enterocytes can capture and internalize antigen:antibody complexes by means of the FeRn on their surface and transport them across the e

24、pithelium by transcytosis. At the basal face of the epithelium, lamina propria dendritic cells expressing FeRn and other Fe receptors pick up and internalize the complexes. Third panel: an enterocyte infected with an intracellular pathogen undergoes apoptosis and its remains are phagocytosed by the

25、dendritic cell. Fourth panel: mononuclear cells have been seen extending processes between the cells of the epithelium without disturbing its integrity. The cell process could pick up and internalize antigen from the gut lumen and then retract. The micrograph shows mononuclear cells, which may be de

26、ndritic cells or macrophages, (stained green with a fluorescent tag on the CD11 c molecule) in the lamina propria of a villus of mouse small intestine. The epithelium is not stained and appears black, but its luminal (outer) surface is shown by the white line. A cell process has squeezed between two

27、 epithelial cells and its tip is present in the lumen of the intestine. Magnification x200. Micrograph from Niess, J.H., eta/.: Science 2005, 307:254-258.參見圖9-7CCR9CCL2547DCCCR947 TSLPRC T腸系膜淋巴結微靜脈MadCAM-1E-鈣粘素E7固有層腸系膜M細胞固有層上皮細胞TT上皮細胞小腸淋巴細胞的激活和歸巢腸系膜淋巴結和派氏集合淋巴結中的DC，在胸腺基質淋巴生成素 (TSLP) 和其它因子的作用下表達視黃醇脫氫酶

28、 (RALDH)，后者將維生素A轉化成視黃酸 (RC)，在RC的作用下，已被抗原活化的效應T細胞（及B細胞）被激發，誘導性表達趨化因子受體CCR9和整合素47，并進入血循環。由于分布在粘膜固有層中的后毛細血管微靜脈的內皮細胞表達MadCAM-1 (47 配體)，使CCR9+47+T細胞停留于該處并穿越微靜脈到達固有層, 并變更其表型為CCR9+E7+T。而固有層上皮細胞表達CCL25 (CCR9配體)和E-鈣粘素（E7配體），使效應性淋巴細胞選擇性地歸巢和停留于粘膜固有層。 Molecular control of intestine-specific homing of lymphocyte

29、s. Left panel: T and B lymphocytes primed by antigen in the Peyers patches or mesenteric lymph nodes arrive as effector lymphocytes in the bloodstream supplying the intestinal wall). The lymphocytes express the integrin 4:7, which binds specifically to MAdCAM-1 expressed selectively on the endotheli

30、um of blood vessels in mucosal tissues. This provides the adhesion signal needed for the emigration of cells into the lamina propria. Right panel: if primed in the small intestine, the effector lymphocytes also express the chemokine receptor CCR9, which allows them to respond to CCL25 (green circles

31、) produced by epithelial cells of the small intestine; this enhances selective recruitment. Effector lymphocytes that have been primed in the large intestine do not express CCR9 but do express CCR10. This may respond to CCL28 (blue circles) produced by colon epithelial cells to fulfill a similar fun

32、ction. Lymphocytes that will enter the epithelial layer stop expressing the 4:7 integrin and instead express the E:7 integrin. The receptor for this is E-cadherin on the epithelial cells. These interactions may help keep lymphocytes in the epithelium once they have entered it.分泌型IgA的特征影響分泌型IgA抗體類別轉換

33、的因素分泌型IgA的轉運分泌型IgA的意義分泌型IgM可以代償有缺陷的IgA 黏膜免疫中的抗體應答腸道中T細胞依賴的IgA 抗體類別轉換機制派氏集合淋巴結圓丘狀隆起部位的DC 獲取由M 細胞提交的腸腔抗原并遷移至濾泡區近旁后，將抗原提呈給初始CD4 T 細胞并使之激活和分化成Th。Th與借助其BCR識別了抗原的B細胞發生相互作用，通過T-B間CD40L-CD40的結合，B細胞分化成產生IgA的漿細胞。該過程受DC產生的一氧化氮及TGF-的促進。由此產生的漿細胞經由血循環再歸槽至固有層，所分泌的高親和力IgA抗體，經過上皮細胞胞吞轉換進入腸腔，與當初致敏的腸腔抗原結合。 CD40L CD40DC

34、初始T激活的ThNOB漿母細胞TGF-經過血流派氏集合淋巴結淋巴濾泡固有層腸腔基底膜上皮細胞腸腔抗原IgAIgA分泌IgA漿細胞DC B7 CD28M 細胞參見圖9-6粘膜DC與炎癥反應Th17與粘膜免疫屏障腸道蠕蟲感染與Th2型免疫應答黏膜免疫中T細胞介導的應答Pathological responses to intestinal helminths. If the CD4 T-cell response to a helminth parasite is polarized to produce predominantly T H 1 effector T cells (for exam

35、ple, by the production of IL-12 by dendritic cells), it does not clear the pathogen. If not balanced by a protective TH2 response, the T H 1 response leads to persistent infection and chronic intestinal pathology. M1 macrophage, classically activated macrophage.Protective responses to intestinal hel

36、minths. Most intestinal helminths induce both protective and pathological immune responses by CD4 T cells. T H2 responses tend to be protective, creating an unfriendly environment for the parasite, and leading to its expulsion and the generation of protective immunity (see the text for details). M2

37、macrophage, alternatively activated macrophage.對腸道蠕蟲感染的保護性應答和病理性應答大部分腸道蠕蟲即可啟動CD4 T 細胞介導的保護性應答也可誘導病理性應答。其中Th2相關應答有利于清除寄生蟲，屬保護性應答；當DC接觸抗原時產生IL-12，則產生Th1型應答。通常兩種應答并存，若Th2介導的保護性應答不能處于優勢地位，Th1型應答將使感染持續，并造成小腸的慢性病理性損傷。置換被寄生的上皮細胞，用粘液阻止寄生蟲粘附，促其脫落。肥大細胞產生TNF, 組胺等介質，募集炎癥細胞, 重塑粘膜。產生能固定補體的抗體IgG2a。活化的巨噬細胞以其產物引起組織損

38、傷，誘導組織重塑。IgE武裝肥大細胞，介導ADCC。嗜堿粒細胞通過主要堿性蛋白 (MBP) 殺傷寄生蟲。激活巨噬細胞招募和激活嗜酸粒細胞驅動 B 淋巴細胞產生 IgE招募肥大細胞，抗蠕蟲驅動B淋巴細胞產生IgG2aIL-13IL-5IL-4IL-9IL-3IFN-誘導上皮細胞修復,分泌粘液.Th-2Th-1DC 初始CD4 T保護效應宿主損傷一、粘膜DC與免疫耐受二、正常腸道的大量共生菌不引發有害的免疫反應三、粘膜耐受的誘導黏膜免疫中的免疫耐受和免疫調節正常腸道的大量共生菌不引發有害的免疫反應腸道共生菌對維持人體的健康發揮著重要的作用。能夠促進食物如纖維素的代謝；能分解毒素；能產生重要的輔助因

39、子如維生素K1和短鏈脂肪酸。通過競爭空間和營養成份可以抑制病原體在腸道的繁殖和入侵共生菌能夠直接作用于黏膜上皮細胞，對維持黏膜的屏障功能有重要作用。共生菌和其產物對于免疫系統的發展和功能有重要作用。 Local responses to commensals. Several local processes ensure peaceful coexistence between the microbiota and the host, allowing the commensal organisms to be recognized by the immune system without i

40、nducing inflammation or an immune response that would eliminate them. Commensal bacteria in the lumen gain access to the immune system via M cells in Peyers patches and isolated follicles (left panel). Uptake and presentation of these noninvasive organisms by resting dendritic cells generates lgA-sw

41、itched B cells that localize in the lamina propria as lgA-producing plasma cells (right panel). The secretory lgA that is produced limits the access of commensals to the epithelium and helps prevent their penetration. This is assisted further by the presence of thick layers of mucus, which also cont

42、ain mucin glycoproteins that have antibacterial properties. In addition, stimulation of pattern-recognition receptors on epithelial cells and local leukocytes induces the production of antimicrobial peptides such as defensins.1mmune priming and tolerance are different outcomes of intestinal exposure

43、 to antigen. Left panel, the intestinal immune system generates protective immunity against antigens that are a threat to the host, such as pathogenic organisms and their products. lgA antibodies are produced locally, serum lgG and lgA are made, and the appropriate effector T cells are activated in

44、the intestine and elsewhere. When the antigen suppressed. This phenomenon is known as oral tolerance and is shown in the right-hand panels, where it has been induced by feeding a protein such as ovalbumin to a normal mouse. First, mice are fed either ovalbumin or a different protein as a control. Se

45、ven days later, the mice are immunized subcutaneously with ovalbumin and an adjuvant; 2 weeks later, systemic immune responses such as serum antibodies and T-cell function are measured. Mice fed ovalbumin have a lower ovalbumin-specific systemic immune response than those fed the control protein. In

46、 the case of commensal bacteria, there is evidence of local lgA antibody production, but no primary systemic antibody responses, and effector T cells are not activated in either site. Profound tolerance of T-cell responses is retained thereafter, but the systemic immune system remains ignorant of co

47、mmensals unless they gain access to the circulation, when a primary systemic immune response will result. is encountered again, there is effective memory, ensuring rapid protection. Harmless antigens such as food proteins or antigens from commensal bacteria induce tolerance, either locally, or both

48、locally and systemically. They lack the danger signals needed to activate local antigen-presenting cells, or do not invade sufficiently to cause inflammation. In the case of food proteins, there is little or no local lgA antibody production or primary systemic antibody response, nor are effector T c

49、ells activated. Subsequent local and systemic immune responses to challenge are also specifically粘膜耐受的誘導A. 健康小鼠飼以卵清蛋白，7天后，用同一抗原加佐劑作皮下免疫，14天后測定小鼠針對卵清蛋白的血清抗體和T細胞應答水平。B. 同一品系的對照小鼠，喂飼無關蛋白，而7天后注射的卵清蛋白屬首次免疫，誘導出的典型保護性免疫針對卵清蛋白。C. B組小鼠以無關蛋白喂飼后若注射同一無關蛋白，同樣可誘導針對該無關蛋白的粘膜耐受。特異應答 7d7d14d14dAB特異應答 粘膜耐受保護性 免疫 7d14d

50、C特異應答 粘膜 免疫一、病原體感染與宿主免疫反應之間的消長 決定了感染的結局二、針對共生菌的免疫應答與腸道疾病三、腸道中與免疫應答相關的一些臨床疾病粘膜免疫與疾病Intestinal pathogens and infectious disease in humans. Many species of bacteria, viruses, and parasites can cause disease in the human intestine.Mucosal infections are one of the biggest health problems worldwide. Most

51、 of the pathogens that cause the deaths of large numbers of people are those of mucosal surfaces or enter the body through these routes. Respiratory infections are caused by numerous bacteria (such as Streptococcus pneumoniae and Haemophilus influenzae, which cause pneumonia, and Bordetella pertussi

52、s, the cause of whooping cough) and viruses (such as influenza and respiratory syncytial virus). Diarrheal diseases are caused by both bacteria (such as the cholera bacterium Cholera vibrio) and viruses (such as rotaviruses). The human immunodeficiency virus (HIV) that causes AIDS enters through the

53、 mucosa of the urogenital tract or is secreted into breast milk and is passed from mother to child in this way. The bacterium Mycobacterium tuberculosis, which causes tuberculosis, also enters through the respiratory tract. Measles manifests itself as a systemic disease, but it originally enters via

54、 the oral/respiratory route. Hepatitis B is also a sexually transmitted virus. Finally, parasitic worms inhabiting the intestine cause chronic debilitating disease and premature death. Most of these deaths, especially those from acute respiratory and diarrheal diseases, occur in children under 5 yea

55、rs old in the developing world, and there are still no effective vaccines against many of these pathogens. Numbers shown are the most recent estimated figures available (The Global Burden of Disease: 2004 Update. World Health Organization, 2008). *Does not include deaths from liver cancer or cirrhos

56、is resulting from chronic infection.1nfection by Clostridium difficile. Treatment with antibiotics causes massive death of the commensal bacteria that normally colonize thecolon. T his allows pathogenic bacteria to proliferate and to occupy an ecological niche that is normally occupied by harmless c

57、ommensal bacteria. Clostridium difficile is an example of a pathogen producing toxins that can cause severe bloody diarrhea in patients treated with antibiotics.病原體感染與宿主免疫反應之間的消長決定了感染的結局Shigella flexneri, a cause of bacterial dysentery, infects intestinal epithelial cells, triggering activation of t

58、he NFB pathway. Shigella flexneri binds to M cells and is translocated beneath the gut epithelium (first panel). The bacteria infect intestinal epithelial cells from their basal surface and are released into the cytoplasm (second panel). Muramyl tripeptides containing diaminopimelic acid in the cell

59、 walls of the shigellae bind to and oligomerize the protein NOD1. Oligomerized NOD1 binds the serine/ threonine kinase RIPK2, which triggers activation of the NFB pathway , leading to the transcription of genes for chemokines and cytokines (third panel). Activated epithelial cells release the chemok

60、ine CXCL8, which acts as a neutrophil chemoattractant (fourth panel). IB, inhibitor of NFB; IK, IB kinase.炎癥性腸炎乳糜瀉食物過敏（I型超敏反應）微生物的持續感染與腫瘤腸道中與免疫應答相關的一些臨床疾病Mucosal dendritic cells regulate the induction of tolerance and immunity in the intestine. Under normal conditions (left panels), dendritic cells