抗原加工与递呈课件

1、第11章 抗原的加工与递呈Antigen Processing & PresentationT cells do not recognise native antigensYYBYYYYYYYBYTYTProliferation and antibody productionNo proliferationNo cytokine releaseCross-linking of surface membrane IgYBYBYBYBYBYBYBCell surfacepeptidesof AgAntigens must be processed in orderto be recognised

2、by T cellsYT T cellresponseNo T cellresponseNo T cellresponseNo T cellresponseNo T cellresponseSolublenative AgCell surfacenative AgSoluble peptidesof AgCell surface peptides of Ag presented by cells that express MHC antigensANTIGENPROCESSINGYTMHC directs the response of T cells toforeign antigensYT

3、AgYTAgAnti responseNo anti responseMHC antigens PRESENT foreign antigens to T cellsCells that present antigen are ANTIGEN PRESENTING CELLSYTYTYTYTYBlockinganti-MHCantibodyYYYAgB细胞浆细胞AbAPCTh细胞Ag肽-MHC分子T细胞Tc细胞Contents 抗原递呈细胞抗原加工递呈途径第一节 抗原递呈细胞Antigen Presenting Cells 基本概念 抗原递呈细胞一、基本概念抗原加工与递呈（Antigen pr

4、ocessing and presentation）抗原加工是指蛋白质抗原在细胞内被降解成能与MHC结合的肽的过程。抗原递呈是指MHC分子与抗原肽结合，将其展示于细胞表面供T细胞识别的过程。Influenza virus内源性抗原（endogenous antigens）指细胞内产生的蛋白质抗原细胞产生的自身固有蛋白质胞内寄生病毒或其它病原体产生的蛋白质细胞恶性转化后产生的突变蛋白，即肿瘤抗原有核细胞内加工，由MHC分子递呈MMMMListeria外源性抗原 (exogenous antigens)指由细胞外进入细胞的蛋白质抗原细胞摄入的各种病原体和疫苗在吞噬体和内体中生长的病原体摄入的自身蛋

5、白抗原递呈细胞内加工，由MHC分子递呈二、抗原递呈细胞抗原递呈细胞 (antigen presenting cell，APC)能够摄取、加工、处理抗原并将Ag信息递呈给抗原特异性淋巴细胞（T细胞）的一类免疫细胞。包括巨噬细胞、树突状细胞、成熟B细胞等广义APC所有有核细胞表达MHC类分子专职APC(professional APC)M，DC，B细胞等表达MHC类分子兼职APC(non-professional APC)内皮细胞，上皮细胞，激活的T细胞等某些因素刺激后表达MHC-类分子1、树突状细胞（dendritic cell, DC）典型树突状形态功能最强的APCDC分类根据起源淋巴系DC滤

6、泡DC (FDC)髓系DC（CD11c+）郎格汉斯细胞 (LC)并指状DC (IDC)并指状树突细胞滤泡状树突细胞B细胞未成熟DC和成熟DC未成熟DC(Immature DC)皮肤、胃肠道、呼吸道等上皮内及实质器官间质内摄取抗原并迁移至引流淋巴器官胞饮（吞饮）受体介导内吞吞噬弱表达低水平的MHC分子、协同刺激分子和粘附分子成熟过程中的重要变化:表达趋化因子受体，获得向引流淋巴结迁移的能力加工递呈抗原，表达大量肽-MHC复合物协同刺激分子和粘附分子表达上调成熟DC(Mature DC)淋巴结，脾及派氏集合淋巴管高表达MHC分子、协同刺激分子及粘附分子很强的抗原递呈能力上皮组织中的LC捕捉外来抗原

7、后即进入引流淋巴结的T细胞区，成为IDC2、巨噬细胞(Macrophage, M)来源、分布前单核细胞（骨髓）单核细胞（血液）巨噬细胞（组织器官）单核细胞体积较大，蹄状核（左，普通光镜）透射电镜显示其高尔基体发达、线粒体丰富、胞浆颗粒明显（中）扫描电镜显示腹腔巨噬细胞粘附于玻璃表面（右）单 核 巨 噬 细 胞功能吞噬消灭病原体加工递呈抗原，激发特异性免疫应答免疫应答的效应细胞M摄取抗原途径胞吞作用吞噬吞饮受体介导内吞模式识别受体 （pattern recognition receptors，PRR）3、B细胞B细胞摄取抗原途径加工递呈可溶性抗原BCR介导内吞特异性高效性第二节 抗原加工递呈途径

8、Antigen Processing and Presentation Pathways MHC类途径 MHC类途径 非经典途径概述T细胞不能直接识别游离蛋白Ag， 只能通过TCR识别Ag肽-MHC分子复合物CD4+T-Ag肽-MHC分子复合物CD8+T-Ag肽-MHC分子复合物YThe site of pathogen replication or mechanism of antigen uptake determines the antigen processing pathway usedYCytosolic compartmentEndogenous processing(Viral

9、 antigens)Vesicular CompartmentContiguous with extracellular fluidExogenous processing(Streptococcal, Mycobacterial antigens)INTRACELLULAR REPLICATIONEXTRACELLULAR ORENDOSOMAL REPLICATIONYEliminated by:Killing of infected cells by CTL that use antigens generated by ENDOGENOUS PROCESSINGYEliminated b

10、y:Antibodies and phagocyteactivation by T helper cells that use antigens generated byEXOGENOUS PROCESSINGAntigens generated by endogenous and exogenous antigen processing activate different effector functionsENDOGENOUS PATHOGENSEXOGENOUSPATHOGENS一、外源性抗原加工递呈途径Exogenous processing and presentation pat

11、hway MHC class pathway 外源性Ag经MHC类分子递呈阶段：外源性抗原的摄取、加工MHC类分子的合成及转运MHC类分子荷肽递呈给CD4+T细胞MHC类途径1、外源性抗原的摄取、加工处理Uptake and degradation of exogenous antigens APC以胞吞作用摄入Ag，形成内体内体与溶酶体融合形成内体/溶酶体Ag被蛋白酶降解成Ag肽抗原加工区室（compartments）YYPinocytosisPhagocytosisMembrane Ig receptor mediated uptakeYComplement receptormediate

12、d phagocytosisYFc receptor mediated phagocytosisUptake of exogenous antigensAPC以胞吞作用摄入Ag，形成内体EndosomesExogenous pathwayIncreasein acidityCell surfaceTo lysosomesUptakeProtein antigensIn endosomeCathepsin B, D and L proteases are activated by the decrease in pH2、MHC类分子的合成及转运Biosynthesis and transport

13、ation of MHC class molecules 粗面内质网中MHC类分子合成与Ii链结合成 (Ii)3复合物Need to prevent newly synthesised, self proteins from binding to immature MHC Invariant chain stabilises MHC class II by binding to the immature MHC class II moleculeIn the Endoplasmic ReticulumMHC class II maturation and invariant chainConc

14、eption i链 a-associated invariant chain，a分子相关的不变链协助类分子折叠和装配阻止类分子与ER中的新合成的肽或内源性抗原肽结合引导类分子进入内体Structure of invariant chainThree extended peptides each bind into the grooves of three MHC class II molecules to form the nonomeric complexCLass II associated Invariant chain Peptide (CLIP) A peptide of the i

15、nvariant chain blocks the MHC molecule binding siteCLIP of invariant chain and b chains of MHC class II moleculesCLIPConception CLIP Class -associated invariant chain peptide ，类分子相关的不变链多肽 i链中81位至104位氨基酸残基的肽段结构 能与所有MHC类分子抗原结合槽相结合3、MHC类分子荷肽Peptide-loading of MHC class molecules i链引导下类分子进入内体(MC) i链降解，类

16、分子肽结合槽中保留CLIP HLA-DM催化，CLIP与肽结合槽解离 HLA-DM编选，高亲和力肽与类分子结合Ag肽-MHC类分子形成EndosomesCell surfaceUptakeClass II associated invariant chain peptide (CLIP)(Ii)3 complexesdirected towardsendosomes byinvariant chainCathepsin L degrades Invariant chainCLIP blocks groove in MHC moleculeMHC Class IIcontaining vesic

17、lesfuse with antigencontaining vesiclesRemoval of CLIP?How can the peptide stably bind to a floppy binding site?Competition between large number of peptidesHLA-DM catalyses the removal of CLIPMIIC compartmentHLA-DMReplaces CLIP with a peptide antigen using a catalytic mechanismSequence in cytoplasmi

18、c tail retains HLA-DM in endosomesHLA-DMHLA-DRConceptionMCMHC class compartment，MHC类分子区室富含外源性抗原肽、 MHC类分子、HLA-DM的低pH值的晚期内体MHC类分子荷肽主要场所 HLA-DM的编选作用 HLA-DM可驱逐与类分子抗原结合槽低亲和力结合的肽，直至有高亲和力的肽与类分子结合，才与类分子分离，使其抗原结合槽恢复闭合状态。 HLA这种对肽的选择作用称为HLA-DM的编选作用，保证类分子递呈高亲和力的外源性抗原肽。4、递呈给CD4+T细胞Presentation of exogenous antig

19、enAg肽-类分子经胞吐作用表达于APC表面供CD4+T细胞识别MIIC compartment sorts peptide-MHC complexes for surface expression or lysosomal degradationSurface expression of MHC class II-peptide complexesExported to the cell surface Sent to lysosomes for degradation 二、内源性抗原加工递呈途径Endogenous processing and presentation pathway M

20、HC class pathway 内源性Ag加工后由MHC类分子递呈阶段：内源性Ag肽的产生及转运MHC类分子荷肽递呈给CD8+T细胞MHC类途径1、内源性抗原肽的产生Generation of endogenous antigenic peptide内源性抗原泛素化经蛋白酶体（LMP）降解为短肽Crystal Structure Of The 20s ProteasomeFrom YeastViewEnd onDegradation in the proteasomeThese components are induced by IFN- and replace constitutive c

21、omponents to confer proteolytic properties The components of the proteasome include MECL-1, LMP2, LMP7LMP2 & 7 encoded in the MHCProteasome cleaves proteins into hydrophobic and basic amino acidsCytoplasmic cellular proteins, including non-self proteinsare degraded continuously by a multicatalytic p

22、rotease of 28 subunits2、内源性抗原肽转运至内质网Transportation of endogenous antigenic peptide into ER经抗原加工相关转运体（TAP）转运至ERERCYTOSOLPeptide antigens produced in the cytoplasm are physically separated from newly formed MHC class INewly synthesisedMHC class I moleculesPeptides needaccess to the ER inorder to be lo

23、aded onto MHC class I moleculesER membraneLumen of ERCytosolTransporters associated withantigen processing (TAP1 & 2)Transporter has preference for 8-15 amino acid peptideswith hydrophobic, basic C terminiTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2

24、PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideER membraneLumen of ERCytosolTAP-1TAP-2PeptideATP-binding cassette(ABC) domainHydrophobictransmembranedomainPeptide antigensfrom proteasome3、MHC类分子荷肽Peptide-loading of MHC class molecules内质网内钙联蛋白、钙网蛋白协助下 MHC类分子合成tapasin协助下MHC

25、类分子与TAP孔道内侧口结合Ag肽-MHC类分子复合物形成Endoplasmic reticulumCalnexin bindsto nascentclass I chainuntil 2-M bindsTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2Peptide2-M binds and stabilises floppy MHCTapasin, calreticulin, TAP 1 & 2 form a complex with the floppy MHCCytoplasmic peptides are loaded onto the MHC molecule and the structure becomes compactMaturation and loading of MHC class I4、递呈给CD8+T