1、DEPARTMENT OF IMMUNOLOGYT淋巴細胞(T lymphocyte)T淋巴細胞概述T淋巴細胞的分化發育T淋巴細胞的表面分子及其作用T淋巴細胞亞群T淋巴細胞的功能主要內容T細胞 (T lymphocyte)淋巴細胞概述T細胞是由一群功能不同的異質性淋巴細胞組成，由于它在胸腺內分化成熟故稱為T細胞。成熟T細胞由胸腺遷出，移居于周圍淋巴組織中淋巴節的副皮質區和脾白髓小動脈的周圍。T細胞執行特異性細胞免疫應答并在TD-Ag誘導的體液免疫應答中發揮重要作用淋巴細胞概述基本概念成年人骨髓每天約產生109個淋巴細胞成年人體內約1012個淋巴細胞，童貞細胞壽命約57周，效應細胞 ：幾天90存

2、在于外周淋巴器官或組織中外周血循環中淋巴細胞約占白細胞總數的2045T細胞占60，B細胞30，NK細胞10T細胞在免疫器官中的比例：淋巴液90，胸腺85，淋巴結75，脾臟35基本數據淋巴細胞的顯著特征：異質性（heterogeneity）發育過程涉及復雜的：發育生物學（developmental biology）研究方法：表型鑒定、各種動物模型建立基本特性T淋巴細胞的分化發育T細胞在胸腺的發育T細胞在外周淋巴器官中的分化發育T細胞受體(TCR)的發育T細胞發育過程中的陽性選擇T細胞發育過程中的陰性選擇thymic corpuscle T細胞在胸腺發育胸腺微環境是誘導并調控T細胞分化發育的關鍵因

3、素 胸腺基質細胞（TSC） 細胞因子 胸腺激素T細胞在胸腺發育TCR的發育DN: b鏈基因開始重排 前細胞替代a鏈pTapTa:b受體表達于preT表面preT增殖活躍分化為DP細胞IL-7pTa:b表達下調細胞停止增殖a鏈基因重排開始表達有功能的TCR雙陰性期（DN） 原T細胞（pro-T）、前T細胞（pre-T）TCR 、CD3 /low 、CD4 、CD8 雙陽性期（DP）TCR 、CD3low、CD4 、CD8 單陽性期（SP）TCR 、CD3 、CD4 TCR 、CD3 、CD8 成熟T細胞，具有識別抗原、介導免疫應答及參與免疫調節的功能1. T細胞發育的陽性選擇（positive

4、selection）CD4+CD8+T細胞胸腺基質細胞（表面MHC分子）如果與MHC-I結合，最終分化為CD8+T細胞如果與MHC-II結合則最終分化為CD4+T細胞如果與MHC分子不結合則在胸腺皮質中凋亡胸腺細胞經陽性選擇賦予成熟T細胞在識別抗原時具有MHC限制性2. T細胞發育的陰性選擇（negative selection）其TCR識別胸腺基質細胞表面高親和力的MHC或MHC-自身抗原肽的T細胞克隆將發生凋亡經陰性選擇可清除自身反應性T細胞克隆獲中樞耐受DP或經陽性選擇的SP的T細胞T細胞在胸腺中的陽性選擇和陰性選擇 T細胞在外周淋巴器官中的分化發育初始細胞細胞亞群調節性細胞記憶細胞T淋

5、巴細胞表面分子及其作用T細胞表面受體 T細胞表面抗原 粘附分子T細胞表面標志MHC抗原 所有T細胞表達MHC-I 活化T細胞表達MHC-II類分化抗原（CD , cluster of differentiation） 與T細胞識別和激活有關：CD3、CD4、CD8、CD2、CD28家族、CD40L、CD45等T細胞表面抗原TCR-CD3 complexTCR-CD3復合物是T細胞抗原受體與一組CD3（Gamma DeltaEpsilon Zeta Eta ）分子以非共價鍵結合而形成的復合物，是T細胞識別抗原和轉導信號的主要單位。TCR特異識別由MHC分子提呈的抗原肽，CD3分子轉導T細胞活化的

6、第一信號CD3 是T細胞所特有的表面標志 與 TCR以鹽橋形式組成 TCR-CD3復合體TCR-CD3 復合體結構模式圖 轉導T細胞活化的第一信號 功能穩定TCR的結構負責抗原特異性信號傳導參與T細胞發育CD4/CD8CD4：胸腺細胞、成熟TH細胞 巨噬細胞、DC等 CD8：胸腺細胞、成熟TC 細胞 NK細胞、T等表達CD4 結構單鏈跨膜糖蛋白分子，胞外區含有4個Ig樣結構域分別為D1、D2、D3和D4CD4分子D1結構域可與HIV gp120結合，是HIV病毒的受體CD4分子的D4結構域能與IL-16結合，有可能為IL-16受體 IL-16: 刺激CD4T細胞、單核細胞及嗜酸性粒細胞的移行，

7、抑制HIV感染的T細胞CD4分子結構示意圖lckCD4和CD8共受體分子模式圖 CD8結構 或鏈以二硫鍵連接的二聚體，每條鏈具有一個IgV樣結構域V樣區與胞膜之間：富含脯氨酸、絲氨酸和蘇氨酸的連接肽，廣泛糖基化，保護多肽鏈免于蛋白酶的裂解CD4通過D1結構域側面與MHC-II類2結構域結合CD8通過鏈V樣結構域與MHC-I類3結構域結合穩定T細胞與APC或靶細胞間的結合CD4和CD8通過胞漿區的CxCP基序與p56lck酪氨酸激酶相連，參與T細胞活化和增殖信號轉導 功能CD4與MHCII結合位點CD28-B7分子家族 CD28家族成員包括： CD28 CTLA-4 （cytotoxic T l

8、ymphocyte antigen-4） ICOS（inducible T-cell co-stimulator） PD-1（ programmed death 1） CD28家族分子配體均為B7家族分子 均屬于IgSF B7家族成員包括：B7-1（CD80）B7-2（CD86）ICOSLPD-L1、PD-L2 CD28B7分子家族 同源二聚體胞外區單一IgSF V樣結構域，具有高度保守的MYPPY基序胞漿區可與多種信號分子和激酶作用胞漿區SH3-激酶結合位點（PYAP），對細胞分化和IL-2的產生重要 CD28 CD28家族分子結構與CD28有31同源性，生物進化十分保守與B7分子結合必需的

9、MYPPY基序CTLA-4與B7結合的親和力明顯高于CD28胞漿區有ITIM（immunoreceptor tyrosine-based inhibition motif）基序，與SHP-2蛋白酪氨酸磷酸酶的SH2結構域結合，募集并活化PTP，阻斷由PTK參與的活化信號轉導通路 CTLA-4 （cytotoxic T lymphocyte antigen-4）分布和功能 CD28分布：組成性表達所有CD4T細胞和50CD8T細胞功能：1)與B7結合提供共刺激信號，促進T細胞活化2)轉導信號與TCR轉導信號起協同促進作用，顯著減低有效活化T細胞所需的TCR數量 分布：初始T細胞不表達，活化后快速

10、上調表達與B7結合親和力高功能：轉導負調節信號，在調節外周T細胞耐受中發揮重要作用 體內阻斷CTLA-4能增強抗腫瘤免疫，加劇自身免疫應答 CTLA-4CD28/CTLA-4B7-1/B7-2結合 ICOS（inducible T-cell co-stimulator）氨基酸水平：與CD28有39同源性胞外區有與ICOSL結合的FDPPPF基序胞漿區特殊基序，可與PI-3K的p85亞單位結合ICOS 區別CD28和ICOS分子及其功能的結構基礎CD28有SH3-激酶結合位點（PYAP）ICOS缺乏此位點，NATURE REVIEWS，VOLUME 2 | FEBRUARY 2002 | 125

11、ICOS T細胞活化后快速誘導表達表達水平受到TCR和CD28信號的影響Th1，Th2分化早期，ICOS均上調表達生發中心中Th細胞高表達ICOS ICOS與CD28所產生的共刺激信號具有協同促進作用 ICOS主要調節已活化的或效應T細胞產生細胞因子增加多種細胞因子分泌不增加CTL的殺傷功能 ICOS對Th2分泌IL-4和IL-13發揮重要作用 ICOS上調Th2表達CD40L，可影響B細胞Ig類別轉化在初始T細胞活化過程中阻斷ICOS，能促進Th1的分化程序性死亡分子-1(programmed death -1, PD-1)無MYPPPY基序，有半胱氨酸殘基，易形成二硫鍵而組成同源二聚體胞漿

12、區含有2個酪氨酸，其中一個參與組成ITIMPD-1L和PD-2L為B7家族新成員，被確定為PD-1的配體 PD-1 PD-1 分布：表達于：活化T細胞、NK、B和髓系細胞表面功能：抑制T細胞增殖 主要機制：拮抗CD28-B7信號途徑，抑制生長因子的分泌 CD2 CD2又稱為淋巴細胞功能相關抗原-2（lymphocyte function associated antigen 2, LFA-2） 與其配體LFA-3 ( CD58 ) 結合CD2分布：胸腺細胞、 T細胞和NK細胞CD58分布：廣泛，T細胞、APC、粒細胞、紅細胞和血小板表面，某些上皮細胞、內皮細胞和成纖維細胞也可表達CD2和CD5

13、8分子結構相似，胞外區N端 ：IgSF V樣區，近膜段：IgSF C2樣區 CD2/CD58功能 增強T細胞與APC或靶細胞的粘附作用 促進T細胞識別抗原及其介導的信號轉導p59fyn 胸腺細胞的分化成熟CD40L（CD154） 結構屬于TNF超家族成員II型膜蛋白分子，C端在胞外區，N端在胞內區 以三聚體形式結合三聚體的CD40 分布活化的T細胞表面（主要CD4+T/部分CD8+T和 T）活化的B細胞、嗜堿性粒細胞、NK細胞、單核細胞等LFA-1/ICAM-1功能 介導T細胞與APC或靶細胞的粘附作用T細胞與APC細胞間的主要輔助分子4. 其它一些受體 絲裂原受體 細胞因子受體 病毒受體1）

14、初始T細胞、效應T細胞和記憶性T細胞 初始T細胞表達CD45RA,CD62Lhigh ， 效應T細胞表達IL-2R,整合素,CD44,CD45RO 記憶性T細胞表達CD45RO,黏附分子(整合素,CD44) NK1.1 T細胞 其TCR識別的抗原是由CD1分子提呈的脂類和糖脂類抗原三、T細胞亞群三、T細胞亞群2）根據TCR種類 T、T細胞在末梢血主要為T細胞可占95%，而T細胞只占1%10%。T細胞為主要參予免疫應答的T細胞，兩者特性和功能均不相同。TCRT和TCRT細胞 TCR 分布 表型識別抗原MHC限制功能TCRT TCRT 極大多樣性60-70,外周淋巴組織成熟CD2CD3CD4/CD

15、8817aa經典MHCTh、Tc較少多樣性5-15,粘膜上皮成熟大多數CD2CD3簡單多肽、 HSP、脂類、多糖MHC樣分子Tc3）根據T細胞是否表達CD4或CD8分類 CD4+ T細胞或CD8+ T細胞TCRTCD4+細胞：CD2+、CD3+、CD4+、CD8-TCR識別抗原是MHC類分子限制性 TH0、Th1和Th2、行使Tc、Ts功能TCRTCD8+細胞：CD2+、CD3+、CD4-、CD8+TCR識別抗原是MHCI類分子限制性 行使Tc、Ts功能Th細胞 根據所分泌的細胞因子不同，將其分為Th1、Th2和Th17亞型。 Th3、I型調節性T細胞(Tr1)Tc細胞 殺傷、分泌IFN、IL

16、-4、IL-5和IL-10Treg4）功能性亞群：Th、Tc(CTL)、Treg初始T細胞效應T細胞記憶T細胞T細胞活化階段abT細胞gdT細胞Th細胞CTL(Tc)Treg細胞CD8T+細胞CD4T+細胞TCR類型CD4/8功能Th1Th2Th17TregGeneration and conversion of Treg cells in the tumor microenvironmentTumor cells not only provide antigenic stimulation for T cell activation but also interact with tumor-

17、infiltrating innate immune cells to secrete crucial cytokines for T-cell differentiation. Nave CD4+ T cells can be differentiated into different subsets of CD4+ T cells, including Th1, Th2, Treg and IL-17-producing T cells (Th17), depending upon the strength of antigen stimulation and cytokine milie

18、u. It is known that combination of suboptimal antigen stimulation with TGF-b favors the conversion of naive T cells into Treg cells but blocks the generation of Th1 or Th2 cells. However, TGF-b plus IL-6 facilitate the conversion of naive T cells intoTh17 cells. Alternatively, naturally occurring CD

19、4+CD25+ Treg cells directly derived from the thymus can cross-react with some antigens expressed by cancer cells, thus promoting their expansion and accumulation in the tumor microenvironment.T-helper-cell differentiationHuman IL-17 and IL-17R key featuresa Two isoforms (long and short). Therapeutic

20、 targets for autoimmune inflammatory diseases are associated preferentially with the IL-23/Th17 pathway The pathogenic role for IL-23, not IL-12, in mouse models of autoimmunityStudies by Cua and co-workers have demonstrated that disease development requires IL-23, but not IL-12, in EAE and CIA. Com

21、pared with wild-type susceptible mice, mice deficient for IL-23 (Il23p19/) and both IL-23 and IL-12 (Il12p40/) failed to develop disease after antigenic challenge, whereas mice deficient for IL-12 (Il12p35/) developed more severe disease.Model of Th1 versus Th17 lineage development from naive CD4 T

22、cell precursors (Tn)This model emphasizes the distinct lineages leading to mature Th1 and Th17 effector cells (see main body of text for details). Question marks denote speculative or unknown aspects of Th17 differentiation that are yet to be defined.Antagonistic cytokine networks control CD4 effect

23、or T-cell differentiationRecent studies have established that Th1 and Th2 effector cytokines, IFNg and IL-4, respectively, potently inhibit Th17 development. Furthermore, TGF-b, a cytokine previously implicated in Treg development and function, appears to be required for Th17 development, both throu

24、gh indirect effects (blockade of IFNg and IL-4 production by cells of the innate immune system) and through direct effects on naive CD4 T-cell precursors (Tn).CD4+T細胞分化和免疫調節細胞因子網絡模式簡圖Although functional CD4 T cell development has been dominated by the Th1-Th2 paradigm for nearly two decades, the num

25、ber of defined lineages has now increased. The cytokines associated with arrows indicate dominant cytokines involved in specification of each of the indicated lineages. The cytokines listed below each cell type indicate key effector or regulatory cytokines produced by differentiated cells of that li

26、neage or, in the case of nTreg, a contact-dependent mechanism of suppression. Tn: naive, postthymic CD4 T cell precursors; Tp: thymic precursors.Dotted lines represent less well-defined lineage relationships.Diversification of CD4 T Cell LineagesModel of Branching Th17 and Adaptive Treg Lineage Deve

27、lopmentThis model emphasizes distinct pathways leading to mature Th17 effector cells or Foxp3+ adaptive Tregs (aTreg), induced by a common requirement for TGF-b but differential effects of IL-6 and IL-23. Naive CD4 T cells (Tn) activated by antigen presented on immature DCs that do not produce IL-6

28、production are induced by TGF-b to express Foxp3 and develop into aTregs (top panel). Tns activated bymature,TLR-activatedDCsthat produceIL-6 are induced by TGF-b to upregulate IL-23R and become competent for IL-17 production and IL-23 signaling. IL-23 signaling induces responsiveness to IL-18 and I

29、L-1, which can act synergistically with IL-23 to induce Th17 cytokineproductionindependently ofTCRstimulation.Alternatively, TCR stimulation by antigen can induce Th17 cytokine production directly,without a requirement for IL-23, IL-1, or IL-18.Dotted lines indicate possible positive feedback loops

30、by which cytokine products of Th17 (IL-6) or aTreg cells (TGF-b1) may reinforce lineage development. CD4輔助性T細胞的功能 CD8殺傷性T細胞的功能調節性T細胞的功能四、T細胞功能細胞因子對Th1和Th2細胞的調節作用Naturally occurring CD4+CD25+ Treg cells (56%) GITR and Foxp3 a cellcell contact mechanismAntigen-induced Tr1 and Th3 cells (IL-10) and/or

31、(TGF-b) ck-dependent mechanism no specific marker has been identified. Adaptively induced CD4+ Treg cells GITR and Foxp3 a cell contact dependent or soluble factor-dependent (other than IL-10and/or TGF-b) mechanismglucocorticoid-induced TNFRfamily related gene (GITR)CD8+ Treg cellsNKT regulatory T c

32、ellsMultiple subsets of Treg cellsNaturally occurring CD4+CD25+Foxp3+ Tregs Development and function of naturally occurring CD4+CD25+ FoxP3+ regulatory T cells (nTregs). Development:bone marrow-derived CD4+ T cell precursors develop naturallyinto nTregs upon beneficial TCR engagement by self-peptide

33、MHC complexes and Foxp3 induction in the thymus. Upon instruction in the thymus, nTregs emigrate into the periphery asfunctionally fully competent cells. Mode of action: upon TCR cross-linking, peripheral nTregs suppress the proliferation and IL-2 production by responder CD25CD4+ or CD8+ T cells in

34、acontact-dependent manner either (a) directly or (b) indirectly via the APC. In addition: nTregs may (c) condition DC to become tolerogenic and turn down the response of conventional T cellson her partExtrathymic induction and function of adaptive regulatory T cells. Adaptive regulatory T cells (aTr

35、egs) differentiate from naive conventional CD4+ T cells either as a result of suboptimal antigenic stimulation by resting/immature DC, theinfluence of suppressive cytokines like IL-10, TGF-b or cell contact-dependent interaction with activated nTregs (infectious tolerance). Their mode of action invo

36、lves both cell contactdependent (Tr1 cells) and contact-independent suppressive activities (Th3 cells). Through the production of IL-10 and TGF-b they convert immature DC into tolerizing APCFig. 3 Role of Tregs in early and late stages of microbial infections. In the stages of an immune response aga

37、inst a microbial infection Tregs behave differently. A Throughout the early phase of the response the suppressive activity of Tregs is turned down by effector T cell-derived IL-2 and microbial components such as TLR-ligands. Tregs respond to the stimulation by mature DC and proliferate.b At the late

38、 stage of the response, when the invading organism is cleared from the host, Tregs regain their suppressive function and participate in the silencing of the T cell response by acting on effector T cells and DC. Possibly, this late activity is also for the proper development ofmemory T cellsTreg-base

39、d immune intervention strategies. Selective manipulation of Treg function is an emerging target for immune intervention strategies to either boost responses in cancer and microbial diseases or suppress those unwanted in autoimmunity, allergy, transplantation and pregnancy disorders. The transientdep

40、letion of Tregs as well as their modulation by microbial agents may allow a transient reduction of Treg activity and enforce anti-tumor responses and immunity against viral infections. On the other hand their selective activation could diminishchronic pathological immune responses掌握TCR分型與結構掌握T細胞發育過程

41、掌握T細胞分群及不同亞群的生物學特性熟悉T細胞表面主要膜分子及其作用了解TCRT細胞和TCRT細胞的異同點教學要求T淋巴細胞對抗原的識別及免疫應答 一、T細胞對抗原的識別 二、T細胞活化的過程 三、效應性T細胞的應答效應 免疫應答的基本過程 抗原識別 抗原受體與抗原的特異性結合免疫應答 抗原識別、反應、效應的全過程免疫反應 免疫效應物質與抗原結合的過程 一、T細胞對抗原的識別T 細胞抗原受體及其識別抗原的特點 只識別表達于APC表面并與MHC分子結合 成復合物的多肽 只識別氨基酸一級序列的多肽線性決定簇 TCR識別抗原受到MHC的限制 CD4+T只識別與MHC-II分子結合的肽段 CD8+T只

42、識別與MHC-I分子結合的肽段T細胞與APC間的相互作用 （一）T細胞與APC的非特異性結合T細胞與APC的非特異性結合 （二）T細胞與APC的特異性結合TCR與APC的特異性穩定結合 （三）T細胞和APC表面共刺激分子的結合CD28/B7、LFA-1/ICAM-1、CD2/CD58等（四）免疫突觸（immunological synapse）中心是TCR和抗原肽-MHC復合物周圍是細胞黏附分子對“筏”狀結構，相互靠攏成簇（一）T細胞活化的第一信號二、T細胞活化的信號要求CD4+T細胞的雙識別（二）T細胞激活的第二信號CD28/B7LFA-1/ICAM-1或ICAM-2CD2/LFA-3CD40/CD40L等T細胞活化的雙信號 CD28/B7促進IL-2基因轉錄、合成缺乏時，T細胞失能（anergy）CTLA4與CD28高同源性，與B7親和力比CD28高20倍，結合后啟動抑制信號，有效制約特異性T細胞克隆的過度增殖（三）細