免疫重点

第一章绪论KEY POINTS✓The Definition of immunology and immunity✓The functions of the immune system✓The difference between innate and adaptive immunity1、免疫（Immunity）：机体识别和排除抗原异物，维持机体生理平衡和稳定的功能。

Immunity:(is the capacity of the host to recognize, respond to and eliminate foreign organisms or substance to maintain the steady state of the body.)2、Functions of immune system1）Immune defense：the resistance to pathogen (microbes and parasites ) invasion.2）Immunologic homeostasis:the ability to eliminate senescent or dying cell of the host .3）Immunologic surveillance：the recognition and elimination of mutant cells and virus-infected cells3、免疫学（Immunology)：研究机体免疫系统组成（免疫器官、免疫细胞和免疫分子）、结构及其生物学功能（生理性和病理性）的学科。

Immunology:is the study of basic structure and biological functions of immune system under physical and pathological conditions.4、免疫应答（Immune response）免疫（淋巴）细胞识别抗原后增殖、分化，产生的应答产物（如抗体和致敏淋巴细胞）参与生理性和病理性效应的过程。

Immune response：A process that naive lymphocyte activate, proliferate and differentiate into effector T cells or produce antibody upon recognition of antigen. This process involves into the physical and pathological effect.第二章抗原KEY POINTS✓Antigen✓Immunogenicity and antigenicity✓Complete antigen and hapten✓Antigen determinant/epitope✓TI-Ag and TD-Ag✓Heterophlile antigen✓Superantigen1、D efinition of antigenAntigen (Ag) is any substance that induces a specific immune response and (or) that reacts with the products of a specific immune response.2. Two basic characteristics of antigen免疫原性（immunogenicity）：The nature of antigen to stimulate an immune response抗原性(Antigenicity):The property of antigen to bind specifically with the corresponding effector cells or antibody1）C omplete antigen（完全抗原）：Immunogenicity+antigenicity2）I ncomplete antigen (hapten,半抗原):Hapten are usually very small molecules which react with antibody but can not initiate an immune response3）Carrier (载体):Carrers are proteins to which small nonimmunogenic antigens, or haptens, can be coupled to render the hapten immunogenic.Carrier + hapten Complete antigen3、抗原决定簇（表位）:Antigenic determinant or epitope：The specific structure of an antigen to which an antibody or TCR/BCR on the lymphocyte can bind.Antigenic valence 抗原结合价:The number of epitopes which combine to the binding site of antibody.4、T cell epitope and B cell epitopeEpitopes recognized by T cells:•Linear determinant (degraded)•8~17 residues•Bind with MHC molecules: agretope（限制位）Epitopes recognized by B cells：•Linear determinant or conformational determinant (natural protein) •6~7 residues•Functional determinant5、Factors influencing immunogenicityPhysical and chemical nature of antigen•molecular weight•Chemical composition and structure•protein, polysaccharides, DNA/RNA and integration•degradabilityContribution of the host•Genetic factors:同种动物不同品系及不同个体对同种抗原产生不同强度的免疫应答。

•Health, age, sex•Method of administration—Dose, route, repetition•adjuvant6、Classification of antigenBased on the nature of antigen:complete antigen and incomplete antigenBased on the need of T cell help in Ab production by B cells: •Thymus (胸腺）dependent antigen (TD- Ag):proteins•Thymus independent antigen (TI- Ag):bacteria lipopolysaccharide (LPS), capsular polysaccharideBased on the kinships between host and antigen•异种抗原 (xenogenic antigen)•同种异型抗原(allogenic antigen)•自身抗原(autoantigen)•异嗜性抗原（heterophile antigen，亦称为Forssman抗原）Common antigen shared by human, animals and /or plants, with no relevance among species.•独特型抗原（idiotypic antigen）Antigen that forms by the unique sequence or structure in the V region of TCR/BCR or of antibody.7、Superantigen(SAg)Molecules that polyclonally activate a large fraction of the T cells by binding to MHC class II molecules and T-cell receptors某些细菌或病毒产物可激活很高数量的T细胞。

Features of SAg:•Potent activator of T cells: Polyclonal activation，5-10% of T cells.•No antigen processing,•No MHC-restrictionBiological significance•Hyper activation of T cell and release of cytokine•Immune supressioncommon superantigen•Bacterial exotoxin (staphylococcal enterotoxin, se)•retrovirus protein第三章免疫器官与组织Key points✓The structure and function of central lymphoid organ -T cell development✓The basic structure and function of secondary lymphoid organ✓Lymphocyte recirculation1、Central lymphoid organs (primary lymphoid organs)The sites of the immune cell development, differentiation and maturation.A.Bone marrow (BM)Development of B cells in the Bone Marrow•Microenvironment of B cell development is required.•Stromal cells including epithelial cells, fibroblast cells and macrophages are required for the development and differentiation of B cells.•Pro-B cells differentiated into Pre-B cell in the presence of stromal cells.⏹Role of Stromal cells in the development of B cells1. Cell-cell contacts between stromal cells and developing B cells2. Secretion of cytokines by stromal cells⏹The process of B Cell Development1. B-cell development goes through stages as the progenitor B cells (pro-B cell)，precursor B cells (pre-B cell) , and immature B cells in the bone marrow.2. Ig-gene is rearranged during B-cell development to produce a functional B-cell receptor.3. Expression of other surface marker.Functions of Bone marrow1.Generation of all blood cells and immunocytes;2.The site of B cell development and differentiation.3.The site of humoral immune response of B cell, especially in secondaryimmune response.B、Thymus•Thymus is the site of T cell differentiation, development and maturation.•DiGorgesyndrom: mutations in genes requried for thymus development. Structure of Thymus•Cortex:Thymus epithelial cells, thymocytes, macrophages;•Medulla:Thymus epithelial cells, thymocytes, macrophages, dendritic cells and hassall's body.Cells in Thymus Microenvironment1. Epithelial cells:Influence the development of thymocyte by two way.A. cell-cell contact:Epithelial express MHC molecules---TCR expressed by thymocytes.B. produce cytokines, such as IL-7, IL-6, GM-CSF etc.2. Macrophage: dispersed, express high levels of MHC molecules.3. Dendritic cell: cortex-medullar junction, high density of MHC.4. Thymocyte: The precursor T cells migrate from bone marrow to thymus and become thymocytes.T cell development in thymusPhenotype alterations during T cell development.（见书P23 笔记）⏹Important events occured in thymus:•TCR gene rearrangement form functional TCR.•Thymocyte selection:✓Positive selection---MHC restriction•Occurred during the stage from DP cells to SP cells.•Depend on the recognition of TCR to self-MHC molecules.✧Thymocyteswhose TCR recognize and combine with self MHC moleculescan differentiate and develop further.✧Thymocyteswhose TCR can not recognize self-MHC molecules undergoapoptosis.✧Positive selection determine self MHC restriction✧MHC molecules play important role in positive selection:MHC class I---CD8+T cellsMHC class II---CD4+ T cells✓Negative selection---Central tolerance•Occurred during the stage of SP cells to mature T cells.•Depend on the interaction of TCR to Ag peptide.✧Positively selected SP cells whose TCRs cannot recognizeself-antigen peptide-MHC complex can develope and differentiateto mature T cells;✧Positively selected SP cells whose TCR recognize and combine withself-antigen peptide-MHC complex with high affinity undergoapoptosis or become clonal anergy;✧Negative selection leads to the self-tolerance.✧Self-peptide plays important roles in negative selection.Thymus function•Development, differentiation and maturation of T cells. •Thymus stromal cells directly interact with thymocytes through adhesive molecules and cytokines.•TCR gene is rearranged to form functional TCR.•Thymocytes undergo Positive selection and determine MHC restriction; •Thymocytes are negatively selected, leading to central tolerance.2、Secondary Lymph node and tissuesA、Lymph nodes:structure•CortexOuter cortex: B cells organized into lymphoid folliclesParacortex: T cells and dendritic cells•Medulla:Medullary cords: macrophages and plasma cellsFunction of Lymph nodes•Sites of mature lymphocyte residence;•The site of immune response;•Take part in the lymphocyte recirculation;•Filter and eliminate foreign antigen;•Generation of Memory T cells and B cells.B、SpleenStructure•Red pulp•White pulp•Peripheral lymphoid sheath (PALS): T cells•Lymphoid follicles : B cellsFunction of Spleen•The site of mature lymphocyte residence, 60%B cells,40% T cells; •The site of immune response;•Produce some immune molecules, such as complement;•Filtration of blood-borne antigens.C、Mucosa-associated lymphoid tissue (MALT)Mucosal tissue are colonized various immune cells that initiate immune response to inhaled or ingested antigens.Function of MALT•The First line of defense against foreign antigen;•The site of immune response;•Participate in delayed hypersensitivity;•The site of sIgA secretion.3、Significance of Recirculation•Promote lymphocytes to contact with antigen throughout the body; •Promote effector cells migrate to inflammation site rapidly; •Promote lymph tissue acquire supplement of new lymphocytes from circulatory pools;•Memory cells can participate in recirculation and secondary immune response.第四章固有免疫细胞Key points✓The functions and important membrane molecules of the mononuclear phagocyte system cells✓The features and functions of NK cells1. PhagocytesA．The mononuclear phagocyte system◆IntroductionPathogen-associated molecular patterns (PAMPs)Molecular patterns common to pathogens but not occurring in mammals. Damage-associated molecular patterns (DAMPs)Components of dead/dying cells and damaged tissues such as HSP, and GMHB1. Recognition receptors (PRRs)Receptors of the innate immune system that recognize PAMPs and DAMPs.◆Important surface molecules on macrophagePRRToll like receptorsMannose receptorsA receptor on macrophages that is specific for mannose-containing carbohydrates that occur on the surfaces of pathogens but not on host cells.ScavengerReceptors on macrophages and other cells that bind to numerous ligands and remove them from the blood. The kupffer cells in the livers are particularly rich in scavenger receptors.Receptors that mediate opsonizationPhagocytes express Fc receptors and CRsMolecules involved in antigen presentationMHC class II molecules and B7 (after activation)MHC class I molecules◆Functions1. Phagocytic activity (and cytotoxicity)Mechanism of killingOxygen-dependent: H2O2 (ROI), NO (RNI)Oxygen-independent: enzymes2. Professional antigen presenting-T cell recognition3. Immune regulation ---Cytokine secretion-IL-1、IL-6、IL-8、IL-12 and TNF-α, et al.Mediate inflammatory reactionAct on NK cells and T cellsB. Neutrophils (polymorphonuclear cells, PMNs)●Membrane moleculesComplement R，CR1, CR3 and CR4.FcγR (FcγRI, FcγRII and FcγRIII)LFA-1 and IL-8R etc.●Functions of NeutrophilsPhagocytosis and cytotoxicity:Direct clearance by phagocytosis.By Fc receptor and complement receptor (opsonization)IgG-Ag—FcγR—phagocytosisIgM---activation of complement→CR→phagocytosis.2、Natural killer cell, NKA. Origin and developmentDerived from lymphoid precursor cells.No TCR/BCR gene rearrangement and expression.Large granular lymphocyte, LGLB. Localization and characteristicsTissue: lymph node and bone marrowCirculation: 5-10% PBL1%~2% splenocyteC. Receptors associated with non-specific killing:✧KIR (killer inhibitory receptors):Binds to MHC class I molecules and prevents the NK from killing.✧KAR (killer activation receptor):Receptors that recognize a wide variety of carbohydrate ligands present on many cells trigger the killing of NK cells in the absence of simultaneous engagement of KIRsD. Function1. Recognize and kill certain tumor cells and virus-infected cellNon-specific killing✧Release of granules which contains perforins and granzymes✧FasL induced apoptosisSpecific killing:expression FcγR (CD16) mediate ADCC ( antibody-dependent cell-mediated cell cytotoxicity)2. Immune regulation (cytokine secretion)IFNγ, TNF, IL-3,GM-CSF,M-CSF,TGF-β✧Activate T cell mediated immunity✧Regulation of hemopoiesis3、Mast cell and BasophilsA. Localization and morphologyBasophils: low number in circulationMast cell: mucosa and connective tissueB．ReceptorsFcεRReceptor of C3a,C5aC.Granule release (degranulation)Activated byBinding to C3a and C5aCross-linking by IgE and allergens via FcεR on their surface MediatorsHistamine: histamine；leukotriene C；prostaglandine D2 Cytokines: TNF, IL-8, PAF etc.D、Functionsfirst-line defense against pathogen invasion (Essential in the development of acute inflammatory response)Immunity against parasitesAnaphylactic response4．Other cells5、Innate like lymphocytesA.B-1 cells✓Arise early in embryonic development.✓Limited set of gene rearrangements to make their receptors.✓Self-renew, long life cells.✓Located in peitoneal and pleural cavities.✓mainly response to polysaccharide antigens (TI-2 Ag) and produce IgM.◆Immune response mediated by B1 cells:Produce IgM at 48h later in response to antigen stimulation.No secondary response, low affinity of antibody, no class switching. No memory, function at early infection.B.γδT cells✓CD4-CD8-T cells；✓TCRs are composed of a γ chain and δ chain.✓Located in skin, mucosa and thymus.✓Limited diversity and lack of recirculation.✓Recognize CD1 presented phospholipids and nucleotides.’◆Functions of γδT cells：Cytotoxicity：→mediate cellular immune response at mucosal sites.Regulatory effect：→release various cytokines（IL-2, IL-3, IL-4, IFN-g, GM-CSF and TNF etc.）→promote B cell activation and antibody production; activate macrophages.Repair injured mucosaNKG2D ( T cells）---combine with MIC-A and MIC-B（injured mucosal cells ）→apoptosis of injured mucosal cells and replaced by normal cells.C.NKT cellsT cells that coexpress NK1.1 and TCR-CD3 complex.majority---TCRαβCD4+T cells；minority---TCRαβCD8+T cellsLocation：lymphoid tissueAntigen recognition：Lack of diversity;Mainly recognized CD1 presentedPolysaccharide and lipid antigens on target cells.NKT cells do generate memory response◆Functions of NKT cells：Regulatory effects:NK1.1T cells+DC+Mφ---determine the type of immune responses, Such as:●some bacteria and virus→DC+Mφ→IL-12→activate NK1.1T cells→IFN-γ+IL-12→Th0 cells →Th1 differentiation.●Parasites→activate NKT cell→IL-4→Th0 cells →Th2 cells→IgE andIgG1.Cytotoxicity: tumor cells killing第五章适应性免疫淋巴细胞——T淋巴细胞Key points✓The important membrane molecules expressed on T cells.✓The classification of T cells.✓The main biological difference among CD4+ T cell subsets.✓The killing mechanisms of cytotoxic T cell.Surface molecules and functions on T cellsA.T cell receptor and CD3 complex–Consists of TCR, CD3 and ζ chain✧(T cell receptor, TCR):–heterodimeric (either αβ or γδ) glycoprotein on thesurface of T cell that enables T cells to recognize a diversearray of antigens. It is associated with the CD3 molecularcomplex.TCRαβ：95% peripheral biood T cell ( conventional T cell) TCRγδ : epidermal and mucosal surface✧CD3: All mature T cellsRequired for signal transduction following antigen recognition by TCR heterodimer.Required for surface expression of the TCR complex at the cell surface. Marker of mature T cells⏹ζchainITAM （immunoreceptor tyrosine-based activation motifs）B. Other surface molecules1. CD4 and CD8 molecules◆CD4: Helper T cell, coreceptorAdhesion molecule , MHCⅡmolecules receptorStimulate intra cellular events that are important in the activation process.Receptor of HIV◆CD8: Cytotoxic and suppressor T cellAdhesion molecule , MHCⅠmolecules receptorStimulate extra cellular events that are important in the activation process.2. CD28 and CTLA-4 (cytotoxic lymphocyte antigen-4)◆CD28: T cellInteract with B7.1 (CD80) and B7.2 (CD86) on APC providingessential costimulatorysignal required for T cell activation.◆CTLA-4: Activated T cellBinding to B7.1 (CD80) and B7.2 (CD86) with a greater affinitythan CD28, resulting in a negativesignal for T cell activation.3. CD2: Thymocyte, Tcell and NKLFA-2: lymphocyte function associated antigen-2ER: Sheep erythrocyte receptor- Adhesion molecule, bind to LFA-3 (CD58)4. LFA-1: Leukocytes- Adhesion molecule, bind to ICAM-1(CD54)5. CD40L (CD154): Activated T cellCostimulatory molecule for B cellC.T cell subsetsTCR•TCRαβT cell, TCRγδT cellCoreceptor•CD4+ T cell, CD8+ T cellFunctional subsets•Th, Ts, TcState of development•Naïve, Primed / activated, memory T cellD. Functions of T cell (TCRαβ)1.Th cell:(T helper cell, CD4+ )Help other cells carry out their functions via direct interact and cytokine secretion.Classified into 4 subsets (Th1 and Th2;Th17 and Treg) on the basis of cytokine secretion.Naive Th is called Th02. Th17 cellsTh17 cell is newly found subset of CD4+ T cells, which distinct with Th1 and Th2 cells.Activated Th17 cells produce IL-17, TNF-a, IL-6 and GM-CSF.Autoimmune diseases3. CD4+ regulatory T cellCD4+CD25+Treg cells:Secret TGF-β and IL-10Express transcription factor Foxp3Inhibit T cell responses4. Tc cell :( Cytotoxic T cell, CD8+)Function•Directly kill the (virus) infected cell and the tumor cell •Immune regulationFeatures of killing•Antigen-specific•Inducing apoptosis of target cells第六章适应性免疫细胞——B淋巴细胞Keypoints✓Roles of surface molecules in B cells activation.✓Biological difference between B1 and B2 cells.✓Function of B cells (B-2)A、Important surface molecules of B cells1. BCR complex●BCR: mIgM, mIgD●Igα (CD79a)Igβ (CD79b)ITAM2. B cell co-receptor complexCD21---C3dR,CR2.CD19--B cell markerCD813．CD40: (B cell, Mφ, dendritic cell)Provide the second signal for B cell activation after engaged by CD154 (CD40L) on activated T cellInduce the class switch of isotype of antibody.4．CD32 (FcγRⅡ)Inhibit B cell activation when binds to IgG-antigen complexes 5．B7 (B7-1/CD80, B7-2/CD86):Costimulatory molecules: Provide the 2 signal for T cell activation B、B cell classificationAccording to the expression of CD5 moleculesB1-B cell (CD5+): innate immunityB2-B cell (CD5－): Conventional B cellStatusNaïve B cellActivated B cellMemorry B cellC、Functions of B -1 cellB1 cells function:✧Recoganization of TI-Ag✧Production of autoimmune antibodies, such as blood type antibody. B2 cells function:✧Antibody productionNeutrolizationComplement activationOpsonization, ADCC✧Antigen presenting—soluble Ag, secondary response✧Cytokine secretion / immune regulation◆Comparison of biological features between B1 and B2 cells第七章抗原提呈细胞Key points✓Definition and classification of antigen presenting cells.✓Phenotype and functions of dendritic cells.✓Antigen presentation of endogenous and exogenous antigen. A．Antigen presenting cell (APC)Definition：APCs are highly specialized cells that can process antigens and display their peptide fragments on the cell surface together with MHC molecules required for T cell activation.Classification ：✧Professional/specialized APC:•Dendritic cells•Macrophages• B cellsB.Dendritic cell1）Origin, distribution and migrationBone marrow ProgenitorCirculation immature DC Tissue immature DC Lymphoid organs mature DC2）Surface molecules-Immature DC is different from mature DC in phenotypeDifferences between immature DCs and mature DCs◆immature DCs：✧Low expression of MHC molecules✧Absent B7 expression✧Unable to stimulate T cells activation.✧Express DEC205 molecules and phagocytosis.◆Mature DCs：✧Express high levels of MHC molecules, both MHC class I and IImolecules.✧Express high levels of B7（B7.1 and B7.2）.✧Produce chemokines, attract and activateT cells.✧No phagocytosis.3) Functions of DCInterface of innate and adaptive immunity◆Immature DC----Unspecific antigen uptake●Phagocytosis on the basis of recognition●macropinocytosis◆Mature DC -----Antigen processing and presentation.Associate with central and peripheral tolerance.Produce cytokine mediating immune regulation.Macrophage:–Similar with DCB cell:–soluble antigen, secondary responseC.Antigen processing and presentingProcess that antigen are degraded by one of two pathways yielding antigenic peptides that bound to MHC molecules are displayed on the surface of antigen-presenting cells.⏹Different antigen-processing and presentation pathways Endogenous antigens (those generated within the cell) are processed in the endogenous pathway and presented on the membrane with MHC class I molecules;Exogenous antigens (those taken up by endocytosis) are processed in the exogenous pathway and presented on the membrane with MHC class II molecules.1）The exogenous pathway✓Peptides are generated from internalized molecules in endocytic vesicles✓In RER, class II MHC molecules are assembled with the invariant chain (Ii) which guides the transportation of class II MHC molecules to endocytic vesicles✓Peptides assemble with class II MHC molecules by displacing li chain ✓Once a peptide has bound, the peptide-class II complex is transported to the plasma membrane2）The endogenous pathway✓Peptides for presentation are generated by proteasomes in the cytosol ✓TAP (transporter associated protein) mediates transportation of peptides into the RER✓Peptides assemble with class I MHC within ER✓Class I molecules-peptide complex exit from the RER, and proceed to the cell surface via the Golgi complex.◆Cross-presentation of exogenous antigens-In certain cases, APCs may present exogenous antigen to cytotoxic T cells in the context of class I MHC molecules.Presentation of nonpeptide antigensThe nonprotein antigens are presented by members of the CD1 family of nonclassical class I molecules◆Presentation of nonpeptide antigensThe nonprotein antigens are presented by members of the CD1 family of nonclassical class I molecules第八章抗体Keypoint✓The basic structure of Ig consists of two light and two heavy chain.✓V regions of the molecules are responsible for antigen recognition，C regions mediate biological function.✓There are five classes or isotypes of heavy chain-g,a,m,d, and e -corresponding to the heavy chains of IgG, IgA, IgM, IgD, and IgE,respectively.✓Generation of Abs diversity results from VDJ recombination duringB cell development and somatic mutation.✓Biofunctional diversity of Abs results from isotype switching.✓McAbs are produced by a single clone of B cell hybridoma and are homogenous in structure and specificity. A．Introductions◆DefinitionsAntibody (Ab):functional conceptAbs are glycoproteins produced by B cells in response to antigen stimulation and have capacity to specially combine with the corresponding antigen.Immunoglobulin (Ig):structural conceptGlobulin proteins have same bioactivity of antibody or have similar structure to antibody.All Abs are Igs, however, not all Igs are Abs.◆Two forms of ImmunoglobulinsMembrane immunoglobulin, mIgB cell receptor, BCRSecreted immunoglobulin, sIgAntibodyB.The molecule structure of antibody1.Basic model:Y-shaped，four peptides2 Heavy chains (H chain)2 Light chains (L chain)✧H chain:•450-550 aa• 5 classes based on structureIgG, IgA, IgM, IgD and IgE✧L chain:•210 aa• 2 types based on structureκand λVariable region (V region)•Hypervariable region（HVR)，or complementary determining region (CDR)•Framework region ( FR)Constant region (C region）•CL•CH1~CH3 (IgG, IgA, IgD)•CH1~CH4 (IgM, IgE)Hinge regionBetween CH1 and CH22.DomainsDiscrete, compactly folded regions compromized about 110 amino acids long of both H- and L-chains bridged by intrachain disulfide bonds. Each domain has particular functional propertyL chain: VLCLH chain: VHCH1, CH2, CH3, CH4Functions of domains3.Antibody fragment generated by proteases (IgG)1)Protease papain(木瓜蛋白酶)Fab (fragment of antigen binding):•complete L chain paired with the VH and CH1 domains of the H chain •antigen binding activityFc (fragment of crystallizable):•the paired CH2 and CH3 domains,•Mediates effector functions such as complement fixation and monocyte binding.•Bearing the isotype antigen.2)PepsinF( ab′)2 ：Combined with 2 epitopespFc′：No biological activities3) Significance: Illustrate the structure and functions of Ig.4.Other components•joining chain ( J chain):IgM and IgA•secretary piece (sp) :a component of sIgAC.Serologic type of immunoglobulin1. Isotype（同种型）:同一种属每个个体都具有的免疫球蛋白的抗原特异性，其抗原决定簇主要存在于Ig的C区。