T cell and Cell-mediated immunity

Transcription

1 T cell and Cell-mediated immunity ( 第十章 第十二章第十二章 ) Lu Linrong ( 鲁林荣 ) PhD Laboratory of Immune Regulation Institute of Immunology Zhejiang University, School of Medicine Medical Research Building B Lu.Linrong@gmail.comLi il Website:

2 T lymphocyte a key player in the immune system Absence or hyperactivation of T cells leads to immunodeficiency, respectively chronic inflammation or autoimmune disorders.

3 T Cell Belongs to Lymphocytes Can be distinguished by the expression of T cell receptor (TCR) Function: mediate cellular immunity; Thymus-derived d lymphocyte: T cell Origin: bone marrow stem cell Distributing: T Zone of secondary lymph node and peripheral blood (65-75% of total lymphocytes)

4 Outline 1. Development of T cells 2. T cell surface markers 3. T cell subsets 4. Functions of T cells 5. Cell-mediated d immunityit

5 1. Development of T cells

6 T cells develop in Thymus

7 Sequential development of thymocytes Pre-T cells: no T cell marker expression Double negative cells (DN): CD4 - CD8 - ; cytoplasmic CD3 + Double positive cells (DP): CD4 + CD8 +, CD3 +, TCRR low, TCR low Mature T cells (single positive T cells): CD4 + or CD8 +, CD3 +, TCR +

8 Stages of T cell development defined by surface markers

9 Surface marker for thymocyte development 25 CD CD44 CD4 CD8 Wang et al Nature Immunology 2012

10 Geography of the thymus: Thymic stroma cells control the maturation of thymocytes

11 Stages of Thymocytes development in Thymus

12 Factors promoting T cell development in the thymus Cytokines (IL-1, IL-6, IL-7) and hormones secreted by thymic stroma cells. Interaction of cell adhesion molecules between immature thymocytes and thymic stroma cells. Notch (1,2,3 are in the thymus) in the context of other stromal cell factors, interacting with its ligand(s) Delta, Jagged or Serrate, plays a role in committing the CLP to T cell lineage

13 The cortical epithelium of the thymus is critical for T cell development The nude mouse strain is athymic due to a mutation in the Foxn1nu gene that encodes FOXN1, a transcription factor of the forkhead box family. FOXN1 is preferentially expressed in the skin and thymus. Alteration ti of its expression in the thymus underlies the manifestation of severe immunodeficiency resulting from total absence of T cell development.

14 Checkpoints in Thymocyte Development TCR arrangement

15 VDJ recombination and TCR expression is essential for Thymocytes development

16 Comparison of Diversity Generated in TCR and BCR Assembly

17 Two Lineages of Cells Expressing Distinct TCRs Develop in the Thymus: Stages of gd and ab T Cell Development Modified from Ciofani and Zuniga-Pflucker, Nature Rev. Immunol., 2010 (C-Kit)

18 Thymocytes development driven by stage-specific expression of Key molecules 代理 a 链

19 Positive and negative selection Positive selection: DP cells that bind to MHC-Ag on thymic stroma cells survive----mhc restriction MHC I----CD8 + T cells MHC II----CD4 + T cells Negative selection: Cells that bind to MHC-Ag on thymic stroma cells (or auto-reactive T cells, ART) with high affinity will undergo apoptosis Formation of central immune tolerance Downloaded from: StudentConsult (on 1 June :58 PM) 2005 Elsevier

20 2. T cell surface markers

21 CDs on T cells

22 CD3 1.Consists of 5 proteins that are designated as,,,,, and. Three dimers:,, ( ) 2.The cytoplasmic domain contains ITAM (immunoreceptor tyrosine- based activation motif) YxxL/V 3 Function: ITAM phosphorylated by lck capable of recruit signaling 3.Function: ITAM phosphorylated by lck, capable of recruit signaling molecules, transduction of signals that lead to T cell activation.

23 transmembrane glycoprotein co-receptor of T cell CD4 and CD8 *CD4: first and second domains bind to nonpolymorphic region of MHC Ⅱmolecules CD8: IgV-like domain of chain binds to nonpolymorphic 3 region of MHCⅠmolecules function: function: mediate adhesion; mediate signal transduction: lck binding and activation first V-like domain of CD4 ---specific receptor of HIV APC

24 CD28 and CD152 (CTLA-4) CD28 + cell ---all CD4 + T cell and 50% CD8 + T cell; CTLA-4 + cell --- activated T cell binding to B7-1 (CD80) and B7-2 (CD86) on the surface of APC *CD28: provide an co-stimulatory signal for T cell * CTLA 4 lifi ti f ti t d T ll (b i * CTLA-4:suppress amplification of activated T cell (bring into play negative regulation )

25 Interaction of CD28 with B7 provide 2 nd signal for T cell activation

26 CD40 and CD40L (CD154) mediate B cell activation

27 Other surface markers ICOS: expressed on activated T cells, binds to ICOSL/B7-H2, costimulation PD-1: ligand PD-L1,PD-L2, mediate inhibitory signal CD2: LFA-2, binds to CD58 and CD48, mediate adhesion and activation LFA-1 and ICAM-1: mediate adhesion between T and APC (or other target cells including endothelial and leukocytes).

28 Summary of T cell surface markers

29 3. T cell subsets 1.CD4 + TandCD8 + T cells; 2.TCR T cells and TCR T cells; 3. Naive T cells, effector T cells and memory T cells; 4.Ths and Tregs

30 CD4 vs CD8 T cells

31 vs T cells

32 T-cell responsep Naïve Effector and Memory T cells

33 Naïve vs memory T cells

34 T cell differentiation

35 4. Functions of T cells 1. CD4 + helper T cells (Th): Th0:Th cells that secrete broad spectrum of cytokines at low level. Th1: produce IL-2 and IFN-, but not IL-4. They are chiefly responsible for cell-mediated immune responses, but can also help B cells to produce IgG2a, but not much IgG1 or IgE; Th2: secrete IL-4, 5, 10, 13, but not IL-2 and IFN-, are very efficient helper cells for production of antibody, especially of IgG1 and IgE. Th17:secrete IL17, 21,22,26 and TNF-, promote anti-bacteria and anti-fungi response. Responsible for inflammatory and autoimmune diseases Tfh: folicular helper T cells, promote B cell to develop into plasma cell and secrete antibodies

36 Th1 vs Th2

37 CD4 T cell mediate immunity effecter functions

38 2. CD8 + cytotoxic T cells (CTL) Function: directly kill target cells (cytotoxicity)

39 3. CD4 + CD25 + regulatory T cells (Tr) Foxp3 positive Function: Down-regulation of immune response by inhibiting the activation and proliferation of CD4 + or CD8 + T cells. Mechanisms: Direct inhibition by contacting target cells. Inhibitory cytokines:il-10,tgf-,et al.

40 5. T cell-mediated immune response

41 Introduction Cell-mediated immunity is the arm of the adaptive immune response whose role is to combat infection of intracellular pathogens, such as intracellular l bacteria (mycobacteria, listeria monocytogens), viruses, protozoa, etc.

42 Phases of T cell responses Antigen recognition phase Activation,proliferation and differentiation phase Effector phase

43 Antigen recognition Ag presentation by APC

44 Interaction between APC and T cell Non specific binding of APC and T cell Specific binding of APC and T cell TCR-peptide-MHC co-receptor-mhc co-stimulatory molecules T cell synapse (immunological synapse)

45 Ligand-receptor pairs involved in T cell activation Adhesion Antigen recognition Signal Signal transduction Signal transduction transduction Adhesion

46 1, Formation of the Immunological Synapse When the TCR complex recognizes MHC-associated peptides on an APC, several T cell surface proteins and intracellular signaling molecules are rapidly mobilized to the site of T cell-apc contact. This region of physical contact between the T cell and the APC has been called the immunological synapse csmac : central supramolecular activation cluster (TCR/CD3, CD2, CD28, PKC lck) psmac : peripheral supramolecular activation cluster (LFA-1, Talin, CD43, CD45, CD148)

47 Signal transduction ti in T cell activation 1.Activation of Src family PTK(p59 fyn, p56 lck ) 2.Phoisphorylation tyrosine of CD3 ITAM 3.Recruitment and activation of Syk family PTK(ZAP- 70) 4.Phoisphorylation h of adaptor LAT and SLP 5.Activation of TF:NFAT, AP-1, NF-κB, Oct-1 6.Transcription and expression of gene :IL-2 et al

48 2.Activation of Src family PTK(p59 fyn, p56 lck ) 3.Phoisphorylation tyrosine of CD3 ITAM

49 4.Recruitment and activation of Syk family PTK(ZAP- 70) 5.Phoisphorylation of adaptor LAT and SLP

50 6.Activation of signal pathways and TFs PIP2 IP3

51 Major signaling pathways & Gene expression 1) PLC- TCR-CD3 ITAM ZAP-70 LAT, SLP-76 PLC- IP 3 Ca 2+ calcineurin NFAT PIP 2 { DAG PKC NF- B 2) Ras-MAP ZAP-70 phosphorylation of LAT and SLP-76 Grb-2 and Sos Ras MAPKK MAPK AP-1 Target genes activated by transcription factors CKs and their receptors CAMs Cell cycle and proliferation i related

52 Activation, proliferation and differentiation The first signal: TCR-antigen peptide-mhc (double recognition) CD4-MHC II or CD8-MHC I The second signal (co-stimulatory signal): Interactions between co-stimulatory molecules APC and corresponding receptors on T cells CD28 B7 on The third signal: Cytokines in T cell activation

53 Two signals ensure T cell activation Co-stimulation provides signal II self antigen

54 The 3rd signal determine the differentiation of Th cells. --Cytokine signal as signal III

55 Differentiation of CD4 T helper (Th) cells) CD4 + T cells: Th1,Th2, Th2 Th17,TregsTregs regulated by cytokines (i (signal 3)

56 Differentiation of CD8 T cells into Cytotoxic T (Tc) cells Th-dependent Th-independent: virus infected DC that highly express co-stimulatory molecules can directly stimulate CD8 + T cells.

57 Effector functions of activated T cells 1) CD4 + T cells Th1: secrete IFN-, activate macrophage express CD40L, help B cells effect on lymphocytes: IL-2 effect on epithelial cells: TNF-, Th2: promote B cell growth and Ig production mediate hypersensitivity Th17: IL-17,IL-8,TNF- : activation epithelial cells and fibroblast, enhance neutrophils recruitment and inflammation

58 Effector functions of CD4 T cells Activation of macrophages by T lymphocytes

59 Activation of Macrophage by Th1 cells

60 2). Effector functions of CD8 + T cells Cytotoxicity: kill target cells a. necrosis: perforin and granzyme b. apoptosis: granzyme, FasL Characteristics of CD8 + T cell cytotoxicity a. Specificity it b. MHC I restriction c. High efficiency

61 CTL Mechanisms 1. Cytolysis (necrosis) i) three stages: a. contact phase: recognition of antigen in the context of MHC class I molecules b. secretory phase: release of cytolytic granules (perforin and granzymes) c. lysis phase: osmotic death

62 CTL Mechanisms 2 CTL 2. Cell apoptosis: a. FasL-Fas: CTLs express FasL interaction with Fas on target cells activation of caspase 8 apoptosis Target

63 3) memory T cells 1) CD45RA - CD45RO + CD44 +, 2) Long-lived memory to specific antigen 3) Mediate faster, stronger and more effective immune response 4) Mechanism: low dependent on costimulatory molecules or more sensitivity to cytokines

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65 Summary 1. Development of T cells: Markers and stages, Essentials; 2. T cell surface markers: Related to Functions 3. T cell subsets: vs ; CD4 vs CD8; Ths.. 4. Functions of T cells: Th1, Th2, CTL; 5. Cell-mediated immunity: Activation of T cells Effector of T cells

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