医学免疫学英文版课件：Chapter12 APC and Processing and Presenting of antigens

1、SummaryMaker of hematopoietic stem cellProcess of B cell differentiationCharacteristic of Ig gene expressionMechanism of Ig diversityProcess of T cell differentiationCharacteristic of TCR gene expressionT cells do not recognise native antigensYYYYYYYBYTYTProliferation and antibody productionNo proli

2、ferationNo cytokine releaseCross-linking of surface membrane IgYBYBYBYBYBYBYBYYBCell surfacepeptidesof AgAntigens must be processed in orderto be recognised by T cellsYT T cellresponseNo T cellresponseNo T cellresponseNo T cellresponseNo T cellresponseSolublenative AgCell surfacenative AgSoluble pep

3、tidesof AgCell surface peptides of Ag presented by cells that express MHC antigensANTIGENPROCESSINGChapter14 APC and Antigen Processing ，Presentation Gao lifen Institute of ImmunologyContents Part Introduction-concepts Part Characteristic of APCs Part Ag Processing and presentation Part Introduction

4、-conceptsEndogenous Ags: antigens synthesized within cells, including self and unself protein-MHC molecules present. Exogenous Ags: antigens comes outside the cell, including self and unself protein-MHC molecules present.Antigen processing: the conversion of native proteins to peptides by APCs, the

5、course of formation of peptide-MHC complexes, display on APC surface.Antigen presentation: the course of peptide-MHC complexes recognition by T cells, transmit Ag signal to T cells and activate T cells.Ag capturing-Endocytosis Phagocytosis, Pinocytosis, Receptor-mediated endocytosis Production of en

6、dogenous Ags and exogenous AgsYThe site of pathogen replication or mechanism of antigen uptake determines the antigen processing pathway usedYCytosolic compartmentEndogenous processing(Viral, tumour antigens )Vesicular CompartmentContiguous with extracellular fluidExogenous processing(Streptococcal,

7、 Mycobacterial antigens)Distinct mechanisms of antigen generation are used to raiseT cells suited to the elimination of endogenous or exogenous pathogensINTRACELLULAR REPLICATIONEXTRACELLULAR ORENDOSOMAL REPLICATIONCell surfacepeptidesof AgAntigens must be processed in orderto be recognised by T cel

8、lsYT 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 antigensANTIGENPROCESSINGAPC Antigen-presenting cells (APC)APC: A group of cells(Accessory

9、cells) play important role in the immune response which can uptake, process antigens and present peptide-MHC complexes to T cells.Professional APC: express MHC molecules Dendritic cell Macrophage B lymphocyte Nonprofessional APC: endothelial cells, epithelial cells, fibroblast, etcAPC Express MHC an

10、d co-stimulatory molecules Uptake, process antigens and present peptide-MHC to T cells Including dendritic cells, macrophages and B cells Part Characteristics of APCs Dendritic cell (DC) Macrophage B lymphocyte1. dendritic cell (DC)History: DCs were first found by Steinman in 1973，named for their sp

11、ecial spinelike projections. DCs were cultured successfully in vitro in 1993 by Inaba.Characteristic: The most efficient APC, can present antigens to naive T cells to elicit primary immune response. Fig2-4 Mature DC suspended in media by colony（ 400） Fig2-5 scattered mature DC（ 400） Scanning electro

12、n micrographIdentification of DC: typical morphologyspinelike projection MLRstimulate nave T cells activation Surface markers : CD1a, CD11c, CD83(human) high expression of MHC co-stimulatory molecules-CD80,CD86 othersCKs, ADs, R(2) Source of DC: pluripotent hematopoietic stem cells myeloid DC myeloi

13、d progenitor lymphoid DC lymphoid progenitor1. dendritic cell (DC)GM-CSF, IL-4(3)Classification of DC : DC in lymphoid tissue: Interdigitating DC(IDC) , Folicular DC (FDC) DC in non lymphoid tissue: Langerhans cell(LC) DC in body fluid:Veiled cell, Blood DC1. dendritic cell (DC)interdigitating DC( I

14、DC ）Express high level of MHCI, II molecules and B7，lack of FcR and CR, can stimulate T cells.FDCB cell folicular DC（FDC）Lie in follicle of LN, no expression of MHCII, high level of FcR and C3bR,present antigens to B cells. Langerhans cells(LC)Birbeck particlelie in the epithelia of the skin and gas

15、trointestinal and respiratory tracts, express FcR and C3bR. After uptaking antigens, migrating to draining LN and becoming IDC.(4)Development and Maturation of DC Pre-DC phase immature DC phase migration phase mature DC phase1. dendritic cell (DC)Pre-DCbloodNon-lymphoid tissuedifferentiationimmature

16、DCDistributeWidely distributed in the bodyPossess ability of Ag capture and process Cytokines and AgDC mature and move into lymphoid tissueability of Ag capture and processing decrease while its ability of Ag presenting increaseDifference between immature DC and mature DCAbility of uptaking and proc

17、essing antigens decrease.Ability of antigen presentation increase.Express high level of MHC, co-stimulatory molecules(CD80,CD86), Ads(ICAM-1).Ability to stimulate nave T cell activation increase.(5) Antigens capturing:Phagocytosiscell , bacteriaPinocytosissoluble antigenReceptor-mediated endocytosis

18、 FcR, C3bR, mannose receptor1. dendritic cell (DC)(6)Function of DC :Capture，process, present antigens-APCStimulate T or B lymphocytesmature DCInduce immune toleranceimmature DC1. dendritic cell (DC)2. Macrophage（ M）Stem from monocytes in blood.Have strong phagocytosis (big phagocyte)Can not stimula

19、te nave T cells Capture antigens by phagocytosis, pinocytosis, receptor-mediated endocytosismonocytes and macrophagesFunction : Phagocytosis Presentation of antigens unactivated macrophage activated macrophage: MHC II molecules and co-stimulatory molecules 2. Macrophage（ M）3. B cellsFunctionsMediate

20、 humoral immune response Present antigens to T cell Soluble Ag-pinocytosis Specific receptor-mediated endocytosisPart Ag Processing and presentation MHC class II pathway -exogenous antigensMHC class I pathway -endogenous antigensCross presentation Section MHC calss II pathway 1. Capture of exogenous

21、 Ag 2. Processing of Ag3. Synthesis and transportation of MHC molecules4. Peptide loading of MHC molecules5. Presenting to CD4+T cells 1. Capture of exogenous Ag endocytosis: phagocytosis: particles or granules pinocytosis: liquids receptor-mediated endocytosis: Form endosome YYPinocytosisPhagocytos

22、isMembrane Igreceptor mediateduptakeYUptake of exogenous antigensComplement receptormediated phagocytosisYFc receptor mediated phagocytosisUptake mechanisms direct antigen into intracellular vesiclesfor exogenous antigen processing1005075250% of max.T cellresponse10-110-210-3Antigen gml-1Receptor-me

23、diatedantigen uptakeNon-receptor-mediated uptakeReceptor-mediated uptake enhances theefficiency of the T cell response 2. Processing of Ag endosome + lysosome Ag antigen peptides(10-30aa) CathepsinProteases produce 24 amino acid long peptides from antigensDrugs that raise the pH of endosomes inhibit

24、 antigen processingEndosomesExogenous pathwayIncreasein acidityCell surfaceTo lysosomesUptakeProtein antigensIn endosomeCathepsin B, D and L proteases are activated by the decrease in pHActivation of Cathepsin B at low pHAt higher pH cathepsin B exists in a pro-enzyme formAcidification of the endoso

25、me alters the conformation of the proenzyme to allow cleavage of the pro-regionLoss of the pro-region exposes the catalytic site of the proteaseHence: drugs that alter acidification of the endosomes disturb exogenous antigen processing3. Synthesis and transportation of MHC II molecules Synthesis of

26、MHC II molecules in ER Ii chain-MHC II molecule (Ii333 ) promote formation of MHCtimer Preventing other peptide from combining with MHC II molecules within ER Leading MHC II molecules into endosome from ER Endosome (MIIC) Ii: invariant chain CLIP : class II associated invariant chain peptideNeed to

27、prevent newly synthesised, unfolded self proteins from binding to immature MHC Invariant chain stabilises MHC class II by non- covalently binding to the immature MHC class II molecule and forming a nonomeric complexIn the endoplasmic reticulumMHC class II maturation and invariant chainInvariant chai

28、n structureThree extended peptides each bind into the grooves of three MHC class II molecules to form the nonomeric complexA peptide of the invariant chain blocks the MHC molecule binding site.This peptide is called the CLass II associated Invariant chain Peptide (CLIP) Invariant chain CLIP peptide

29、and b chains of MHC class II moleculesCLIP4. Peptide loading of MHC II molecules Ii-MHC II molecules protease Ii chain cleaving CLIP-MHC II molecules HLA-DM CLIP releasingAntigen peptide-MHC II complexesEndosomesCell surfaceUptakeClass II associated invariant chain peptide (CLIP)(inv)3 complexesdire

30、cted towardsendosomes byinvariant chainCathepsin L degrades Invariant chainCLIP blocks groove in MHC moleculeMHC Class IIcontaining vesiclesfuse with antigencontaining vesiclesRemoval of CLIP?How can the peptide stably bind to a floppy binding site?Competition between large number of peptidesHLA-DM

31、catalyses the removal of CLIPMIIC compartmentHLA-DMReplaces CLIP with a peptide antigen using a catalytic mechanism (i.e. efficient at sub-stoichiometric levels)Discovered using mutant cell lines that failed to present antigenHLA-DO may also play a role in peptide exchangeSequence in cytoplasmic tai

32、l retains HLA-DM in endosomesHLA-DMHLA-DR5.Presenting to CD4+T cells antigen peptide-MHC II molecuels presented on cell membrane by exocytosisMIIC compartment sorts peptide-MHC complexes for surface expression orlysosomal degradationSurface expression of MHC class II-peptide complexesExported to the

33、 cell surface (t1/2 = 50hr)Sent to lysosomes for degradation section MHC I pathway1. Processing of endogenous Ag2. Transporting of antigen peptide into ER3. Peptide loading of MHC I molecules4. Presenting to CD8+T cells1. Processing of endogenous Ag proteosome : 20S, 26S low molecular weight polypep

34、tide(LMP) : LMP2, LMP7 Ag antigen peptides(8-13aa) Degradation in the proteasomeThe components of the proteasome include MECL-1, LMP2, LMP7These components are induced by IFN- and replace constitutive components to confer proteolytic properties.LMP2 & 7 encoded in the MHCProteasome cleaves proteins

35、after hydrophobic and basic amino acids and releases peptides into the cytoplasmCytoplasmic cellular proteins, including non-self proteinsare degraded continuously by a multicatalytic protease of 28 subunitsCrystal Structure Of The 20s ProteasomeFrom YeastViewEnd on2. transporting of antigen peptide

36、 into ERTAP(transporter associated with antigen processing): Consisting of TAP1 and TAP2 ATP dependent transporter Selective transporting ENDOPLASMIC RETICULUMCYTOSOLPeptide antigens produced in the cytoplasm are physically separated from newly formed MHC class INewly synthesisedMHC class I molecule

37、sPeptides needaccess to the ER inorder to be loaded onto MHC class I moleculesER membraneLumen of ERCytosolTransporters associated withantigen processing (TAP1 & 2)Transporter has preference for 8 amino acid peptideswith hydrophobic C termini.TAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1T

38、AP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideTAP-1TAP-2PeptideER membraneLumen of ERCytosolTAP-1TAP-2PeptideATP-binding cassette(ABC) domainHydrophobictransmembranedomainPeptide antigensfrom proteasome4. Presenting to CD8+T cells antigen peptide-MHC I molecuels presented on cell membrane by exocytosis