Advanced molecular immunology Adaptive Immunity. 03/23/2011

Transcription

1 Advanced molecular immunology-2011 Adaptive Immunity Youmin Kang Tel: Lab: CLS Room /23/2011

2

3

4 Components of immunity it innate adaptive cellular l neutrophils Tl lymphocytes monocytes- macrophages, DC, NK cells humoral complement antibodies acute phase (B lymphocytes) proteins (CRP,MBL..)

5 Innate vs. adaptive immunity Innate immunity First line of defense Immediate (0 4 hours) Non-specific Does not generate lasting protective immunity Adaptive (acquired) immune response (late: > 96 hours) Is initiated if innate immune response is not adequate (> 4 days) Antigen-specific immunity Generates lasting protective immunity Humoral and cell-mediated

6 Adaptive Immunity Features Highly specific for the invading organism Discrimination between self and non self molecules The response only occurs to non self molecules Diversity - It can respond to millions of different antigens - Lymphoctes population consists of many different clones (one cell and its progeny) - Each clone express an antigen receptor and responds only to one antigenic epitope

7

8 Unmethylated CpG motif Toll like receptors

9 Specificity of Ag Ab1 Ab2 Ab3

10 Antibody-Antigen Interactions

11

12 Compare Epitope Structures

13 Classification of antigenic determinant (1)According g to the structure of Ag determinants Conformational determinants Sequential (or linear) determinants

14

15

16

17 (2)According to types of cells recognizing antigenic determinants T cell lldeterminants t (T cell epitopes) B cell determinants (B cell epitopes)

18 MOLECULES OF LYMPHOCYTE RECOGNITION Although B and T cell receptor genes are rearranged similarly to generate a high degree of specificity for antigen, the receptors see antigen in entirely different ways. T-CELL B-CELL Ig Ig CD3 Surface Ig Complete molecule (conformational epitope) 1 1 MHC 2 2 TCR Processed peptide (linear epitope) ANTIGEN PRESENTING CELL

19 CD4 T-CELL CD3 CD8 T-CELL CD3 CD4 TCR CD8 TCR MHC CLASS II aa peptide 2 1 MHC CLASS I 3 9 aa peptide 2 m ANTIGEN PRESENTING CELL ANTIGEN PRESENTING CELL

20 Adaptive Immunity

21 Humoral Immunity 胸腺非依赖性抗原 (thymus independent antigen, TI 抗原 ) 胸腺依赖性抗原 (thymus dependent antigen, TD 抗原 )

22 TD 抗原和 TI 抗原的比较 TD 抗原 TI 抗原 本质 多数为蛋白质 重复排列的长链聚合物 刺激 B 细胞产生抗体是否需要 T 细胞 + - 参与产生抗体的类型 主要 IgG IgM 引起细胞免疫 + - 免疫记忆性 + -

23 Production of antibodies Signal 1 Pathogen (virus or bacteria) Pathogen is internalized and degraded B cell Signal 2 B cell binds pathogen IFN-g,IL-4,IL-5 Tfh Plasma cells T H MHC II B cell B cells differentiate into Peptides from the pathogen B cell antibody-secreting are presented (MHC II) to proliferation plasma cells the T cell resulting in the activation i of the B cell Produce antibodies against pathogen

24

25 Cell mediated d Immunity Involves T cells that act against foreign cells or tissue T cells mature in the thymus gland Alsoregulate the activation and proliferation of other immune system cells Cell mediated immune response is directed against bacteria and viruses inside phagocytic cells or infected dhost cells, fungi, protozoa, and dhelminths h This also causes rejection in implanted tissue

26 B Y Cross-linking of surface membrane Ig B B B Y Y Y Y Y Y B BYB B B B Y Y YY Y Y Y Y Y Proliferation and antibody production T T N lif ti No proliferation No cytokine release Y Y T cells do not recognise native antigens

27 Antigens must be processed in order to be recognised by T cells YT Y Soluble native Ag Cell surface native Ag Soluble peptides of Ag Cell surface peptides of Ag Cell surface peptides of Ag presented by cells that express MHC antigens ANTIGEN PROCESSING No T cell response No T cell response No T cell response No T cell response T cell response

28 Early evidence that antigens are catabolised M M Macrophages and radiolabelled Listeria monocytogenes Rapid binding to cell surface M Internalisation M Degradation of bacteria and release of Radiolabelled protein into supernatant and cells How is antigen catabolism linked to T cell proliferation?

29 The interaction of T cells with macrophages requires antigen catabolism Listeria-specific T cells T NO T CELLS BIND Listeria coated plastic Listeria i NO T CELLS BIND NO T CELLS BIND NO T CELLS BIND T CELLS BIND M M M M 0mins 60mins T cell do not bind stably to antigen presenting cells unless the antigen is catabolised

30 Only metabolically active cells can process antigen Listeriaspecific T cells T M M M Fix with paraformaldehyde or poison with sodium azide Pulse with Listeria for 60min & wash cells Add Listeria specific T cells NO T CELLS BIND catabolic activity is dependent upon the viability of macrophages Antigen presenting cells must be viable to PROCESS antigen APCs?

31

32 Phenotype and location of DC subsets

33 A general model for interaction between DC Subsets and T cells during infection.

34

35 Stages of endogenous and exogenous antigen processing UPTAKE Access of native antigens and pathogens to intracellular pathways of degradation DEGRADATION Limited proteolysis of antigens to peptides ANTIGEN-MHC COMPLEX FORMATION Loading of peptides onto MHC molecules l ANTIGEN PRESENTATION Transport and expression of peptide-mhc complexes on the surface of cells for recognition by T cells

36 Uptake of exogenous( g ( 外源的 )antigensg Membrane Ig receptor mediated uptake Y Phagocytosis Complement receptor mediated phagocytosis Pinocytosisi Y Fc receptor mediated phagocytosis Uptake mechanisms direct antigen into intracellular vesicles for exogenous antigen processing

37 Exogenous pathway Cell surface Uptake Protein antigens In endosome Endosomes Increase in acidity To lysosomes Cathepsin B, D and L proteases are activated by the decrease in ph Proteases produce ~24 amino acid long peptides from antigens Drugs that raise the ph of endosomes inhibit antigen processing

38 Surface expression of MHC class IIpeptide complexes Exported to the cell surface Sent to lysosomes for degradation MIIC compartment sorts peptide-mhc complexes for surface expression or lysosomal degradation

39

40 Non-lysosomal antigen processing Inactive virus raises a weak CTL response The processing of antigens from inactive viruses is sensitive to lysosomotrophic drugs ANTIGENS FROM INACTIVE VIRUSES ARE PROCESSED VIA THE EXOGENOUS PATHWAY Infectious virus raises a strong CTL response The processing of antigens from infectious viruses is NOT sensitive to lyosomotrophic drugs Most CTL recognise antigens generated via a non-lysosomal pathway Protein synthesis is required for non-lysosomal antigen processing ANTIGENS FROM INFECTIOUS VIRUSES ARE PROCESSED VIA THE ENDOGENOUS PATHWAY Do the two pathways generate the same type of T cell receptor ligand?

41 Degradation in the proteasome Cytoplasmic cellular proteins, including non-self proteins are degraded continuously by a multicatalytic protease of 28 subunits The components of the proteasome include MECL-1, LMP2, LMP7 These components are induced by IFN- and replace constitutive components to confer proteolytic properties. LMP2 & 7 encoded in the MHC Proteasome cleaves proteins after hydrophobic and basic amino acids and releases peptides into the cytoplasm

42 Peptide antigens produced in the cytoplasm are physically separated from newly formed MHC class I ENDOPLASMIC RETICULUM Newly synthesised MHC class I molecules CYTOSOL Peptides need access to the ER in order to be loaded onto MHC class I molecules

43 Transporters associated with antigen processing (TAP1 & 2) Lumen of ER ER membrane Peptide Hydrophobic transmembrane domain Cytosol Peptide Peptide antigens from proteasome ATP-binding cassette (ABC) domain Transporter has preference for >8 amino acid peptides with hydrophobic C termini.

44 Maturation and loading of MHC class I Peptide Peptide Peptide Endoplasmic reticulum Calnexin binds B2-M Tapasin, calreticulin, lin TAP Cytoplasmic peptides to nascent class I chain until 2-M M binds binds and stabilises floppy MHC 1 & 2 form a complex with the floppy MHC are loaded onto the MHC molecule and the structure becomes compact

45 Fate of MHC class I Exported to the cell surface Sent to lysosomes for degradation d

46

47 The site of pathogen replication or mechanism of antigen uptake determines the antigen processing pathway used Y EXTRACELLULAR OR ENDOSOMAL REPLICATION Vesicular Compartment Contiguous with extracellular fluid Exogenous processing (Streptococcal, t Mycobacterial antigens) INTRACELLULAR REPLICATION Cytosolic compartment Endogenous processing (Viral antigens) Distinct mechanisms of antigen generation are used to raise Distinct mechanisms of antigen generation are used to raise T cells suited to the elimination of endogenous or exogenous pathogens

48 Three pathways of antigen presentation How DCs activate T cells?

49 Intravital two-photon imaging g of T-cell DC interactions a b

50 c Intravital two-photon imaging of T-cell DC interactions

51 c

52 Activation of CD8+ T cells by DCs in the lymph node high velocities 7.3 new T cells 1 DC/ minute rapid shape changes T cell migration promotes very efficient scanning of the T cell repertoire by an individual DC. NATURE IMMUNOLOGY 2003,4:579

53 Priming of CD8+ T cells by DCs occurs as long-lasting lasting interactions free engaged with DCs 42 T cell-dc interactions Average duration-11 minutes P14 TCR T cells Q: DC density? Green-P14 TCR T cells red -DCs pulsed with 1 μm of gp33 peptide Slow crawling of the T cells on the DC surface; passive movement of the T cell owing to shape changes of the DCs. NATURE IMMUNOLOGY 2003,4:579

54 Impact of DC density on T cell-dc contacts DCs was virtually saturated with P14 T cells One DC NATURE IMMUNOLOGY 2003,4:579

55 Low-avidity interactions result in inefficient recruitment of peptide-specific T cells by antigen bearing DCs 75 individual P14 TCR T cells DCs-high densities of peptide: marked by green arrows; DCs-low densities of peptide: marked kdby red arrows. NATURE IMMUNOLOGY 2003,4:579

56 T cell cluster formation

57 T cell-dc contacts antigen absence : DCs different T cells/hour; antigen-bearing: i DCs T cell simultaneously; l interaction: hours, not minutes, low DCs density, high peptide density.

58 Rapid Formation of Stable CD8+ T Cell-DC Contacts in the Lymph Nodes Immunity 2010, 33:412

59 The Two-Signal Model of T-cell Activation DC T cell CD4 or CD8 1 MHC TCR 2 COSTIMULATION An important costimulator - CD28

60 Costimulation signaling T cell 3

61 IFN- IL-4 IL-2 YYYYYY YYYYY B cells

62 Effector Th cell differentiation

63 The discovery of T FH cell

64

65 Spleen

66 Human TFH in a lymph node from a patient with angio-immunoblastic T cell Lymphoma ( 血管原始免疫细胞性 T 细胞淋巴瘤 ). Note the interactions between PD-1+ (in green) and CD4+ (in blue) Tfh cells and CD20 (in red) B cells (confocal microscopy x500). haematologica 2010; 95(3):356

67

68

69 Q: Tfh-cytokines?

70 TFH cells express distinct genes from TH1, TH2 and TH17 cells KLH( 昆虫血蓝蛋白 )/ CFA; CD4+CD44hiCXCR5+BTLA+ (TFH) cells were sorted and restimulated with anti-cd3 for 4 hours for gene profiling analysis Immunity. 2008, 29(1): 138

71 TFH cells express distinct genes from TH1, TH2 and TH17 cells real-time PCR analysis OT-II cells-anti-cd3 Immunity. 2008, 29(1): 138

72 ELISA Th2 Th1 Intracellular staining Th17 Immunity. 2008, 29(1): 138

73 Generation of TFH cells is independent of TH1 and TH2 lineages CD4+ T cells from CD45.2/OT-II mice were transferred into C57BL/6 (CD45.1) mice OVA/CFA KLH/CFA Immunity. 2008, 29(1): 138

74 IL-21 is necessary for TFH cell development Q: Tfh-costimulator-B7H? Immunity. 2008, 29(1): 138

75 B7H expressed on B cells is required for generation of TFH cells ELISA B7h BKO:B7h B-cell conditional knockout Q: Tfh-cytokines? Immunity. 2008, 29(1): 138

76 Generation of TFH cells requires IL-6 and STAT3 Q: Tfh-Bcl-6? Immunity. 2008, 29(1): 138

77 Bcl-6 Is Required for Tfh Cell Formation In Vivo SRBC (sheep red blood cells) immunization group A: Bcl6 +/+ CD45.1:Bcl6 +/+ CD45.2 group B: Bcl6 +/+ CD45.1:Bcl6 -/- CD45.2 fetal liver chimeric mice Immunity 2009, 31:457

78 Bcl-6 Is Required for Tfh Cell Formation In Vivo C mixed bone marrow chimera mice SRBC (sheep red blood cells) immunization group A: Bcl6 +/+ CD45.1:Bcl6 +/+ CD45.2 group B: Bcl6 +/+ CD45.1:Bcl6 -/- CD45.2 fetal liver chimeric mice Immunity 2009, 31:457

79 Important tmolecules l for Tfh cell llfunction. Annu. Rev. Immunol :741

80 Extrafollicular and Follicular pathways to humoral immunity

81 Pre-Tfh can either enter the follicle to become GC Tfh or interact with plasmablasts outside the follicle.

82 signaling lymphocyte activation molecule (SLAM) lymphoid tissue inducer (LTi) cells: CD4+CD3- Accessory cells localised at the T/B border and within the follicles Cellular interactions required for Tfh formation and maintenance

83 The signaling pathways in TFH cells J Immunol 2010, 184: 6563

84 References 1. Philippe Bousso. T-cell activation by dendritic cells in the lymph node: lessons from the movies. Nature Reviews Immunology 2008,8: Philippe Bousso, Ellen Robey. Dynamics of CD8+ T cell priming by dendritic cells in intact lymph nodes. Nature Immunology 2003,4: He le`ne Beuneu, et al. Visualizing the Functional Diversification of CD8+ T Cell Responses in Lymph Nodes.Immunity 2010, 33: Camille Laurent, et al. A novel subset of T-helper cells: follicular T- helper cells and their markers.haematologica 2010; 95: Julia Rolf, et al. Signaling Pathways in T Follicular Helper Cells. J Immunol 2010, 184: Cecile King, et al. T Follicular Helper (TFH) cells in Normal and Dysregulated Immune Responses. Annu. Rev. Immunol : Di Yu, et al. The Transcriptional Repressor Bcl-6 Directs T Follicular Helper Cell Lineage Commitment. Immunity,2009,31: Roza I. Nurieva, et al. Generation of follicular helper T cells is mediated by IL-21 but independent of TH1, TH2 or TH17 lineages. Immunity. 2008, 29: 138

85