B细胞激活概要课件.ppt

1、 B B 细胞激活细胞激活B Cell ActivationB 细胞抗原识别受体与信号转导细胞抗原识别受体与信号转导T-B 细胞相互作用与细胞相互作用与B细胞的增殖分化细胞的增殖分化B 细胞的增殖与分化细胞的增殖与分化B细胞对细胞对T细胞非依赖抗原的应答细胞非依赖抗原的应答B 细胞抗原识别受体与信号转导细胞抗原识别受体与信号转导1 chapter nine B Cell Activation 图图12-3 抗抗BCR抗体的交联与抗体的交联与B细胞激活信号的产生细胞激活信号的产生抗抗BCR抗体的Fab片段虽与BCR结合但无交联作用,不产生激活信号抗抗F(ab)2的抗抗体与F(ab)2段交联使大量

2、BCR聚合,产生强激活信号抗抗BCR抗体的F(ab)2片段能与BCR交联,产生激活信号Ig-IgFabF(ab)2 anti-F(ab)2BCRT细胞抗原识别信号的转导细胞抗原识别信号的转导 pathway Apathway B pathway CPKCcalcineurinMAP kinasePIP2 DAG +IP3 Ras-GDP Ras-GTP Ca2+RafPLC-SosNF-ATOCTNF-BAP-1NF-ATOCT PKC Grb-2I-BNF-BNF-BNF-AT NF-AT-p c-Jun c-FosAKTB7CD28 PI 3-KLATSLP-76ZAP-70Peptide

3、-MHCTCR Lck FynCD45 CD4 PTPdomainsY505pITAMITAMYpYpNUCLEUSCELLMEMBRANEIL-2 geneYpYpYpGSK3GadsNCK细胞骨架重排细胞骨架重排免疫突触免疫突触PIPI P3BCR Ig/Ig ITAM受体交联（形成免疫突触）受体交联（形成免疫突触）偶联偶联PTK活化活化（LynLyn、FynFyn、BlkBlk）ITAM ITAM 磷酸化（活化）磷酸化（活化）招募胞浆招募胞浆PTK（Syk）PTK磷酸化磷酸化（活化）（活化）衔接蛋白（衔接蛋白（BLNK、SLP-65）PLC-PIP2DAG +IP3激活激活PKC活化钙调

4、磷酸酶活化钙调磷酸酶活化活化MAP激酶激酶级联反应级联反应活化转录因子（活化转录因子（NF-B、NFAT、AP-1）与特异性基因的启动子结合，启动基因转录与特异性基因的启动子结合，启动基因转录转位转位GEF（Vav）CD81(TAPA-1)CD19 Y AgC3dgCD21(CR2)Ig/IgBCRTCRMHC CD4BlkZAP-70LckFynLynSykpeptideAPCT cellB cellA comparison of antigen-recognition structures and the related moleculesin T cell and B cellmain

5、component T cell B cellMembrane antigen receptor TCR BCRmolecule ITAM-bearing molecule CD3,Ig,Ig co-receptor CD4 or CD8 CD21,CD19,CD81 PTP CD45 CD45PTK Src family Lck,Fyn Lyn,Fyn,Blk,Lck Syk family ZAP-70 SykMAPK-related initiation adaptor LAT,SLP-76 BLNK,SLP-65 pathway small G protein Ras(Rac)Rac(R

6、as)GEF Sos Vav MAP kinase Erk JnkSecond signal receptor CD28 CD40 ligand B7 CD40LPTK:protein tyrosine kinase;PTP:protein tyrosine phosphatase;MAP:mitogen-activated protein;GEF:guanine nucleotide exchange factor;LAT:linker for activation of T cell;BLNK:B cell linker protein;ZAP:zeta chain-associated

7、protein;ITAM:immunoreceptor tyrosine-based activation motifA comparison of main components in signal transduction for T and B cells Erk-and Jnk-pathways in MAP kinase-related signaling cascade?PakRafMekkMekLnkkErkJnkFosJunAP-1RasRac,cdc42 T activation B activation/StressGTP proteinMAPKKKKMAPKKKMAPKK

8、MAPKTranscriptionfactorp38T-B 细胞相互作用细胞相互作用与与B细胞的增殖分化细胞的增殖分化 chapter nine B Cell Activation 2BCRhaptencarrierTH 2CkCk-RCD40LCD40lysosomeIi chainMHC class IIAbT、B淋巴细胞分别识别载体和半抗原，通过相互作用诱导抗体产生Agsignal 1Bcellendoplasmic reticulumsignal 2BTH CD40L CD40 CD28 B7Ck(e.g.IL-4)BCRIg-IgAgCollaboration between T c

9、ell and B cell Second signals for B cell activation:ligated CD40 and Ck receptor AbMTOC:microtubule-organizing centerWhen an activated helper T cell encounters an antigen-binding B cell,it becomes polarized and secretes IL-4 and other cytokines at the point of cell-cell contact.Contact of Th2 cell w

10、ith B cellThThBBT细胞对细胞对B细胞的辅助没有特异性细胞的辅助没有特异性T细胞识别细胞识别B细胞所提呈抗原是其辅助的前提细胞所提呈抗原是其辅助的前提T细胞通过细胞通过CD40L和和CK辅助辅助B细胞时极化并紧密接触细胞时极化并紧密接触T、B细胞的相互作用具有特异性但不排除旁邻辅助细胞的相互作用具有特异性但不排除旁邻辅助 B 细胞的增殖与分化细胞的增殖与分化 chapter nine B Cell Activation 3B B细胞在淋巴结的定居、激活、增殖、分化细胞在淋巴结的定居、激活、增殖、分化与生发中心形成与生发中心形成体细胞高频突变与抗体亲和力成熟体细胞高频突变与抗体亲和

11、力成熟抗体类别转换抗体类别转换浆细胞、记忆浆细胞、记忆B B细胞与再次应答细胞与再次应答B B细胞在淋巴结的定居、激活、增殖、分化细胞在淋巴结的定居、激活、增殖、分化与生发中心形成与生发中心形成 Germinal center,the place where B cells differentiateHEV：高内皮小静脉初级初级淋巴滤泡淋巴滤泡次级次级淋巴滤泡淋巴滤泡生发中心生发中心髓索髓索HEV:high endothelial venule(高内皮细胞小静脉高内皮细胞小静脉)SLC(secondary lymphoid chemokine)for receptor CCR7 on T ce

12、ll and DCMIP-3 (macrophage inflammation protein-3)for receptor CCR7 BLC(B lymphocyte chemokine)for receptor CXCR5 on B cellThe cellular organization of a lymphoid organ,which is orchestrated by chemokinesEarly and late events in humoral immune responses to T cell-dependent protein antigensActivation

13、 and migration of T and B cellsT-B cellinteractionB differentiation;Ig secretion,isotype switchingGerminal center reaction;affinity maturation,memory B cellsAntigen-binding cells are trapped in the T cell zone of the lymph nodeto form a primary focus（原发灶）（原发灶）Schematic presentation of a germinal cen

14、ter 边缘区边缘区 中央细胞中央细胞滤泡树突状细胞滤泡树突状细胞中央母细胞中央母细胞T 协助细胞（协助细胞（Th2)B B细胞在淋巴结的定居、激活、增殖、分化细胞在淋巴结的定居、激活、增殖、分化与生发中心形成与生发中心形成(结构结构)体细胞高频突变与抗体亲和力成熟体细胞高频突变与抗体亲和力成熟AffinitybetweenAg-Abreactionand equilibriumconstant KAffinity maturationgood fitpoor fitapplying the Law of Mass Action 蛋白质抗原多次免疫后抗体含量和抗体亲和力明显上升，这一上升主要针

15、对 IgG 而非IgM抗体Affinity maturation亲和力成熟主要发生在二次免疫应答Antibody levelAntibody affinityDay 1Day 21Day 7Day 14Secondary immunizationimmunizationDNADNADNADNADNADNADNADNADNADNA脾脾细胞建系DNA扩增DNA测序分析抗体重链和轻链基因核苷酸序列变异性的实验步骤1/1000bp vs 1/1071010Day 1Day 21Day 7Day 14Secondary immunizationimmunizationB1AgT细胞高频突变细胞高频突变B

16、2B3B1AgAgAg选择选择B2AgIg亲和力成熟亲和力成熟中低亲和力中低亲和力高亲和力高亲和力Somatichypermutationin centroblastsAffinitymaturationIsotypeswitchingdark zonelight zonelight zonelow affinityapoptosishigh affinityFDC:follicular dendritic cell CentrocyteCentroblast(activated B cell)B cellsSelection of high affinity centrocytes by b

17、inding to Ag-Ab complexes on FDCslow affinityPlasmablastPlasma cellMemory cellMacrophageMaturation to memory orplasma cellsAb Germinal Center After T-cell dependent activation,B cells undergo rounds of mutation and selection for higher affinity,ultimately resulting in high-affinity memory B cells an

18、d antibody secreted from plasma cellsMutation and selection in maturation of antibody affinityAgAb 1st response 2nd responsemoderate affinity(10-8 L/M)high affinity(10-10 L/M)抗体类别转换抗体类别转换NeutrolizationOpsonizationC activationcomplementThree effective functions of specific anti-bodies Ig heavy chain

19、isotype switchingIsotype switch takes place during the second response of antibodiesImmunoglobulin levels in newborn infants fall to low levelsaround six months of ageMolecularmechanismsof heavy chainisotype switchingMain factors responsible for isotype switching of antibodies A.Antigen properties -

20、soluble antigens:IgG1 -polysachride antigens:IgM,also IgG2,IgG3 -worm antigens:IgE B.Expression of CD40 on B cells(induction of second signal)-mutation of CD40L expression deficiency failure of isotype switch X-linked hyper IgM syndrome C.Administration routes of antigens into body and adjuvants -or

21、al administration(mucosal immunization):IgA -subcutaneous or intramuscular injection:IgG -immunization with Freud adjuvant(弗氏佐剂弗氏佐剂):IgG -immunization with aluminium adjuvant:IgE D.Cytokines BTH CD40L CD40 CD28 B7CkBCRIg-IgAgproliferationdifferentiationX-linked hyper IgM syndrome caused by the defec

22、tiveexpression of CD40 ligand on T cells,resulting in no second signal for B cell differentiation and isotype switching Patients with X-linked hyper IgM syndrome are unable to fully activate their B cells.B cell activation by T cells is required both for isotypeswitching and for the formation of ger

23、minal centers.Critical roles of cytokines in isotype switch of immunoglobulin Cytokine IgM IgG1 IgG3 IgG2b IgG2a IgE IgA IL-4 -IL-5 -IFN-TGF-Influences of cytokines on isotype switching of antibodies浆细胞、记忆浆细胞、记忆B B细胞与再次应答细胞与再次应答 intrinsic inducible B lineage surface MHC Ig growth somatic isotype cel

24、l Ig class II secretn mutation switch Resting +-+B cell Plasma -+-cell Plasma cell secrete antibody at a high rate but can no longer respond to antigen or helper T cells M:mitochondria E:rough endoplasmic reticulumMembrane and secreted forms of immunoglobulins are derived from heavy-chain sequence b

25、y alternative RNA processingpAs pAmpoly A:聚腺苷酸 记忆记忆B 细胞细胞(Bm)的一些特点的一些特点 初次接触抗原一个月后 产生(Tm五天后产生)，并长期存在；Bm 诱发的二次应答仍 需要 已活化Th2 的协助；和初始B细胞一起参与 外周循环，可聚集在某 些外周免疫器官，如脾 脏滤泡、淋巴结、结合 淋巴结(Peyers patch)；Bm和初始B细胞显示 不同的表面标志。A comparison of nave and memory B cells1Property Nave B cell Memory B cell1Membrane marks im

26、munoglobulin IgM,IgD IgM,IgG,IgA,IgE complement receptor low highAnatomic location spleen BM,lymph node,spleenLife span short-lived long-livedRecirculation yes yesReceptor affinity lower higher due to affinity maturationAdhesion molecules ICAM-1 low high Why long-lived are the antigen-specific memor

27、y lymphocyte clones?A.Persistence of retained antigens,bound to iccosomes of follicular dendritic cells,might be crucial.B.There are cross-reaction between the newly entering antigens and the antigen originally sensitizing the memory cells.C.Cytokines such as those produced either constitutively or

28、during the course of antigen-specific immune responses could be responsible for dividing of memory cells to maintain the memory cell clones in an antigen-non-specific manner.Possible mechanisms for maintenance of the antigen-sensitized memory cellsAntigen can be retained within follicular dendritic

29、cells for a long timein a form of Ag-Ab complex antigen Antigenic Antigenic“Original Sin”Original Sin”and memory B cells and memory B cells2y5y20yB细胞对胸腺非依赖抗原的应答细胞对胸腺非依赖抗原的应答 chapter nine B Cell Activation 4 TD antigen TI-1 antigen TI-2 antigen Ab production in athymic mouse +Ab response in absence o

30、f T +Capable of priming T cells +Polyclonal B cell activation +Requires repeating epitopes +Examples of antigen protein LPS dextran(葡聚糖葡聚糖)（脂多糖脂多糖）polysucrose(聚蔗糖聚蔗糖)BTH2 BTD AgTI AgProperties of different classes of antigen Properties of different classes of antigen that elicit antibody responsesth

31、at elicit antibody responsesTI-1 antigens are polyclonal B cell activators at high concentrations,whereas at low concentrations they induced an antigen-specific antibody response B cell activation by TI-2 Ag is greatly enhanced by cytokines,which can also induce isotype switching Gal (1-3)gal (1-4)glcNAc-R gal-gal-(1-4)glcNAc R 半乳糖 乙酰乳糖胺 糖脂 （半乳糖-乙酰氨基葡萄糖）猪-人异种移植超急排斥抗原半乳糖转移酶基因的进化和非协调性异种器官移植中的超急性排斥 超急排斥猪人非协调性异种器官移植超急排斥抗原半乳糖转移酶基因 +异种天然抗体(XNA)低等 高等 哺乳 新世 旧世 类动物 动物 动物 界猴 界猴 人猿 人类GT半乳糖基转移酶(GT,galactosyl transferase)超急排斥抗原HAR猪血管内皮细胞猪血管内皮细胞人血流人血流