T-cells Monika Raulf T-cell-mediated immunity T-cell regulation T-cell development Lecture 02.05.2018
Stimulation of the T-cells by an antigenpresenting cell Antigen 1. Signal T-Lymphocyte TCR MHC+ Peptide APC CD28/ CTLA-4 CD 80/86 2. Signal Monika Raulf 2
Different features of the MHC-molecules Expression MHC class I on all nucleated cells of the body MHC class II on professional antigenpresenting cells Activation of CD8 + T-cells of CD4 + T-cells Genloci HLA-A, HLA-B, HLA-C HLA-DR, HLA-DP, HLA-DQ Structure transmembrane, α-chain associated with β2- microglobulins transmembrane, heterodimer of α- and β-chain Peptide max. 8-10 amino acids long at least 13 amino acids long Loading in endoplasmatic reticulum in intracellular vesicle Monika Raulf 3
MHC class I- and class IImolecules extracellular domain *2 Structure of the MHC class I- molecule Structure of the MHC class IImolecule consists of α-chain + β2- microglobulin *1 *1 12 kd; not polymorph *2 belongs to the immunoglobulin superfamily Monika Raulf 4
Genetic organisation of the main histocompatibility complex in humans HLA-Locus (human leucocyte antigen) in humans on chromosome 6 z.b. TAP 1, 2 MHC-molecules are polymorph transmembrane glycoproteins. β2-microglobulin (is part of the MHC-class I-molecule, but not located on chromosome 6) Monika Raulf 5
MHC-II Way of presentation Antigen MHC-II Invariant chain with CLIP-fragment (red) proteolytic enzymes Receptormediated Phagocytosis Endosome FE Antigen-presenting cell IE ER MIIC Golgi FE = early endosomes IE = intermediate endosomes ER = endoplasmatic reticulum MIIC = MHC-loaded compartment Monika Raulf 6
Antigens, which are detected of T-cells, possess two different interaction areas Agretope interacts with the MHC-molecule Epitope Interacts with the TCR Class II-MHC Agretope TCR Epitope Monika Raulf 7
Tasks of the T-cells killing (killer cells) somatic cells that are affected by a virus or malignant degenerated (e.g. tumour cells) release messengers (cytokines) Subgroups of T-cells due to gene expression patterns Surface molecules γδ-t-cells αβ-t-cells = Main players of the cellular immune defence CD4-cells CD8-cells Th1 Th2 Monika Raulf 8
Modell of TCR and the associated CD3-complex TCR: αβ-heterodimer extracellular domain Homologous to Ig constant and variable region TCR = defines the antigen specificity CD3 = is necessary for the transport of the whole complex to the cell surface as well as for the signal transduction after cell activation Monika Raulf 9
TCR rearrangement TCR located on chromosome 14 (in humans) Locus: 70 Va + 61 Ja genes + 1 Ca-Gen more than 100 Kb Monika Raulf 10
Destiny of the thymocytes γ:δ TCR Prä-TCR γ:δ TCR γ:δ TCR γ δ β pta Double negative T-cells rearrange their γ-, δ- and β- genes Prä-TCR The γ:δ-t-cell receptor sends out signals, which switch off the β- chain-gene and allocate the cell to the γ:δ-cell line γ:δ TCR Prä-TCR The pre-t-receptor sends out signals, which switch off the γ- and δ-chain-genes and allocate the cell to the α:β-cell line The γ:δ-t-zelle maturates and moves in the periphery α:β TCR Based on the gene rearrangement of the α- chains of the T-cell receptor the mature α:β-t-cell receptor arise Monika Raulf 11
T-cell development in the thymus Origin: hematopoietic progenitor cell -multipotent- DN1 Final aim: T-cell DN2 DN3 DN4 γδ Leave the thymus without repertoire-selection γδ are CD4 CD8 multipotent flexible TCR-genes of the δ-, γ- and β-loci are restored complete restored TCRgenes but only 1/3 of all rearrangements are productive (+), i.e. β + γδ β - γδ β + γδ β - γδ DN4 in proteins adapted β-chain + invariant pre T cell α-molecule + CD3-signal complex mature to CD4 + CD8 + CD4 + CD8 + TCR α-genes restore and express the mature αβ-tcr exists the thymus Th1 Th2 peripheral lymphatic organ Monika Raulf 12
T-cell-mediated immunity naive T-cells primary immune response can act on the target cell Development of the T-cells in the thymus completed mature T-cells in blood circulating arrive at the peripheral lymph organs/ lymph tissues until they detect their specific antigen on APC-cell proliferation and differentiation of the naive T-cell Daughter cells = armed T-effector cells contribute to the disposal of the antigens Monika Raulf 13
Movement, activation and effector function of the lymphocytes depend on the adherence molecules Cell contact with non-antigen specific interaction Requirement: complementary disposal of adherence molecules Selectins, integrins and members of the immunoglobulin superfamily are important (see also movement of the monocytes/neutrophils) Monika Raulf 14
Selectins: important for the homing (e.g. leukocytes can reach their destination by moving to specific tissues); e.g. on naive T-cells: expression of L-selectin (CD62 L) The interaction of L-selectin with vascular adressins (e.g. CD34), which are expressed on endothelium, is responsible for the specific homing of naive T-cells to the lymphatic organs; but this does not mean, that the endothelial barrier to the lymphatic tissue can be break down; therefore the integrins and proteins of the Immunglobulin-superfamily are necessary Cell surface molecules of the Ig-superfamily are important for the interaction of lymphocytes with APC Monika Raulf 15
Stabilisation of the connection between T-cell and APC via specific antigen recognition LFA-1 = lymphocyte function-associated antigen-1 Monika Raulf 16
The activation of T-cells modifies the expression of some cell surface molecules Cell surface molecules CD4- T-cell L-selectin (CD62L) VLA-4 LFA-1 CD2 CD4 T-cell receptor CD44 CD45RA CD45RO inactive + - + + + + + + - active - + ++ ++ + + ++ - + from: Immunologie, Janeway et al. Monika Raulf 17
Co-stimulatory interaction between T-cell and APC T-cell B-cell immunological zip CD80 /CD86 belong to the B7-molecules; interact with CD28 and effect the clonal proliferation of the T-cells Monika Raulf 18
MHC-II CD4 T-helper interaction co-stimulation (naive T-cells) 1. T-cell receptor 2. CD4 3. CD28 4. CD40 ligand 5. Others (CD2/integrins) 6. Cytokines - MHC-II peptide complex - MHC class II - B7 (B7-1=CD80/B7-2=CD80) - CD40 - Others (LFA-3/adhesins) - Cytokine receptors Monika Raulf 19
Anergy antigen recognition without co-stimulation Monika Raulf 20
Microbial substances can cause a co-stimulating activity in macrophages from: Immunologie, Janeway et al. Monika Raulf 21
CD4 & CD8 bind on MHC Helper T-cell Cytotoxic T-cell APC The immunological zip target cell Monika Raulf 22
Helper T-cell APC Cell-cell adherence molecule - binds on MHC class II and stabilizes the TCR/MHC complex - binds on the β2 domain of the MHC protein CD4 transduces signals in the T-cell CD4 is a receptor for HIV Monika Raulf 23
Cytotoxic T-cell Exists of two α-chains or of αβ-chains CD8 is an cell-cell adherence molecule CD8 transduces signals in the T-cell target cell Monika Raulf 24
The three most important T-effector cells synthesize different effector molecules Monika Raulf 25
T-cell mediated cytotoxicity The Fas-ligand (CD95L) is the most important membrane bound and with TNF-related molecule, expressed by cytotoxic T-cells. It is able in cells expressing the receptor Fas (CD95*), to trigger the programmed cell death (= Apoptosis). How does apoptosis look like? Nucleus comes apart Cell morphology changes DNA is digested Fragments with 200 Bp (Activation by endogenous nuclease) Rejection of membrane-bound vesicle During the apoptosis program the host cell is killed and also the pathogen in the cytoplasm; meaning that the nucleases don t digest just the cellular DNA, but also the viral DNA *Fas belongs to the cytoplasmic end of a death domain, which is able to trigger an activation cascade of cellular proteases (caspases) Monika Raulf 26
The different stages of the activation of CD4-T-cells Naive CD4-T-cell (uncommitted) Activated proliferating T-cell Activated T-cell not determined (T H 0) T H 1-cell T H 2-cell Activation of macrophages; B- cells produce antibodies of the isotype IgG1 Activation of B-cells, they produce antibodies of IgE, IgG4; activation of eosinophilic granulocytes from: Immunologie, Janeway et al. Monika Raulf 27
At least four different groups of CD4 + regulatory T-cells play, e.g. for asthma bronchial, a role Naturally occurring Treg Adaptive Treg Monika Raulf 28
Differentiation and regulation of T-helper cells T H 1 T-bet STAT-4 γ-ifn, TNF T H IL-12 IL-4 TGF-β IL-23 TNF IL-27 T H 2 GATA-3 STAT-6 T H 17 RORγT IL-4 IL-17 IL-6 T reg Foxp3 TGF-β Monika Raulf 29
Functionally T-cell population Monika Raulf 30
Example how the Th1-/Th2-difference has an effect on the course of an infection Lepra tuberculoid lepra lepromatous lepra Monika Raulf 31
Example how the Th1-/Th2-difference has an effect on the course of an infection Lepra Mycobacterium leprae-infection tuberculoid lepra M leprae grows in macrophage vesicles; macrophages are activated by Th1-cells; just a few bacteria measurable, just a few antibodies; inflammation damages skin and peripheral nerves; patient survives mostly lepromatous lepra Antibody-development by humorale reactions, activated by Th2-Zellen; antibodies cannot reach bacteria in the macrophages, can breed unimpeded; Result: widespread, most lethal tissue destruction Monika Raulf 32
Cytokines Cytokinereceptor are the hormones of the immune system they exert their effect through cytokine receptors they are pleiotropic, meaning one cytokine is able to induce different effects; has different features they mediate the most different processes in the immune system Cytokine Monika Raulf 33
Production site of the cytokines and chemokines APZ T-cells IFN-α, TNF-α, TGF-β, IL-1, IL-6, IL-8, IL-10, IL-12, MCP-1, MIP-1, GM-CSF, M-CSF IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-15, GM-CSF, IFN-γ, TNF-β, MIP-1β, RANTES, TGF-β B-cells TNF-β, MIP-1β IL-12 Mast cell IL-4, IL-5, CD40-ligand Monika Raulf 34
Functional classification of cytokines Natural immunity Activation, growth, differentiation lymphocytes APZ T-cell B-cell IFN-α, TNF-α, IL-1, IL-6, IL-8 Activation inflammation cells IL-2, IL-4, TGF-β, IL-10 Activation hematopoiesis Eos Neut Native cell IFN-γ, IL-5, IL-9, MIF IL-3, GM-CSF, M-CSF, IL-7 Monika Raulf 35
Cytokines, which are build in the early phases of an infection, influence the functional differentiation of CD4-T-cells CD4/Th1 CD40- ligand In presence of IFNγ and IL-12 Th1-cells develop cytokines IFN- γ GM-CSF TNF-α CD40-ligand Fas-ligand others IL-3 TNF-β (IL-2) one reason: IFN-γ inhibits the proliferation of Th2-cells Monika Raulf 36
Development of Th2-cells In the presence of IL-4* and also IL-6 active CD4-cells develop to Th2-cells CD4/Th2 CD40- ligand cytokines IL-4 IL-5 CD40-ligand others IL-3 GM-CSF IL-10 TGF-β IL-10, IL-4 and TGF-β inhibit the activation and proliferation of Th1-cells * IL-4 originate potentially from NK1.1+-T-cells (subgroup of the CD4-positives) CD4/Tr1** ** T regulatory 1 cells Monika Raulf 37
Th2-cells activate, especially at primary reactions, highly effective B-cells. Th1-cells are in contrast crucial for the macrophage activation. Is a specific subgroup of the CD4-T-cells in the course of the immune response primarily or preferential activated, it can eliminate the development of each other; meaning at specific immune responses prevails therefore either the humoral (Th2) or the cellular (Th1) defence. In vivo are however often situations, in which both defence reactions occur (all initially researches on a mouse model); influence of the balance by cytokines. Also at CD8-T-effector cells there are respective subpopulations (Tc1 or Tc2). Monika Raulf 38
Species and amount of the antigen peptides can also influence the differentiation of CD4-T-cells naive T-cell Th2 Low affinity Minor density of peptides on the surface of APC induce Th2-response, also peptides, which bind just weak on the TCR Monika Raulf 39
naive T-cell Th1 High affinity High density of peptides on the surface of APC induce Th1-response, also peptides, which interact intensive with the TCR. Monika Raulf 40
Nomenclature and functions of well characterised T-cell cytokines I Cytokine T-cells (source) B-cells T-cells Effect on Effect of the gene-knockout Macrophages Haematopoietic cells Other somatic cells Interleukin-2 (IL-2) T H 0, T H 1, some CTL stimulates growth and synthesis of the J-chain Growth stimulates growth of the NK-cells T-cellresponses, IBD* Interferon-γ (IFN-γ) T H 1, CTL Differentiation; IgG2a-synthesis inhibits the growth of T H 2-cells Activation, MHC-class I and MHC-class II activates NK-cells anti viral; MHC-class I and MHC-class II susceptible to mycobacteria Lymphotoxin (LT, TNF-β) T H 1, some CTL inhibits kills activates, induces NOproduction activates neutrophils kills fibroblasts and tumour cells Lymph nodes are missing, spleen structure abnormal Interleukin-4 (IL-4) T H 2 Activation, growth, IgG1, IgE, induction of the MHC-class II Growth, survival inhibits macrophageactivation Growth of mast cells no T H 2 Interleukin-5 (IL-5) T H 2 Differentiation, IgA-synthesis Growth and differentiation Interleukin-10 (IL-10) T H 2 MHC-class II inhibits T H 1 Inhibits release of cytokines co-stimulates the growth of mast cells IBD from: Immunologie, Janeway et al. *IBD = inflammatory bowl disease Monika Raulf 41
Nomenclature and functions of well characterised T-cell cytokines II Effect on Cytokine T-cells (source) B-cells T-cells Macrophages Effect of the gene-knockout Haematopoietic cells Other somatic cells Interleukin-3 (IL-3) T H 1, T H 2, some CTL Growth factor for precursor haematopoietic cells (multi-csf) Tumour necrosis-factorα (TNF-α ) T H 1, some T H 2 and CTL activates, induces NO-production activates microvascular endothelia Resistance against gramnegative sepsis pathogens Granulocytemacrophagecolony stimulating factor (GM- CSF) T H 1, some T H 2 and CTL Differentiation inhibits growth Activation, differentiation to dendritic cells Development of granulocytes and macrophages (myelopoiesis) and dendritic cells Transformation of the growth factor β (TGF-β ) CD4-Tcells inhibits growth; factor for the IgAclass switching inhibits activation activates neutrophils inhibits/ stimulates cell growth Death after approximately ten weeks from: Immunologie, Janeway et al. Monika Raulf 42
Cytokine receptors belong to several families of receptor proteins, which have each different structures Receptors for erythropoietin, growth hormone and IL-3 Cytokine receptors of class I (family of the erythropoietin receptors) Cytokine receptors of class II Family of the TNFreceptors Family of the chemokine receptors Receptors for IL-3, IL-5 and GM-CSF have the same chain, CD131 or β c (same β-chain) Receptors for IL-2, IL-4, IL-7, IL-9 and IL-15 have the same CD132- or γ c -chain (same γ-chain); IL-2-receptors have besides a third chain, a high affinity IL-2Ra-(CD25-) subunit Interferon-α, -β- and -γ-receptors, IL-10-receptor Receptors I and II for the tumour necrosis factor (TNF); CD40, Fas (Apo1), CD30, CD27, receptor for the nerve growth factor CCR1-5, CXCR1-4 Monika Raulf 43
Infections Allergens Mast/Baso IL-4 + Th2 IL-3, IL-4, IL-5 IL-13, GM-CSF TGF-β Th0 - IL-12 / IFN-γ IL-4 / IL-10 Lectine Genes IL-12 Monocyte + IFN-γ Th1 IL-2, IFN-γ, TNF-α, GM-CSF Monika Raulf 44
The immune response against intracellular bacteria is coordinated by activated T H 1-cells activated T H 1-cell IFN-γ and CD40- ligand Fas-ligand or TNF-β IL-2 IL-3 + GM- CSF TNF-α + TNF-β MCP-I activates macrophages to eliminate absorbed bacteria kills chronic infected cells; bacteria are released to be eliminated by new macrophages Induces a proliferation of T-cells, whereby the amount of effector cells increases induces in bone marrow the differentiation of macrophages activates the endothelia that macrophages bind on it and leave the blood vessel at the site of infection Motivates macrophages to accumulate at the site of infection Monika Raulf 45
T-effector cells regulate effectively all known effector mechanisms of the acquired immune response Monika Raulf 46
The course of a typical acute infection from: Immunologie, Janeway et al. Monika Raulf 47
Immunological processes of an infection Adhesion to the epithelia Local infection, transition of the epithelia Local infection of the tissue Proliferation in the lymph system Adaptive immune response Normal flora Local chemical factors Phagocytosis (especially in the lung) Wound healing Anti bacterial proteins and peptides Phagocyte γ-δ T-cells Complement (alternative way), Phagocytes, Cytokines, NK-cells, Activation of macrophages Phagocytes, Capture of antigens, NK-cells Specific antibodies, T-cell-dependent activation of the macrophages, cytotoxic T-cells Monika Raulf 48
The wide range of different pathogens has lead to the fact, that in the course of the evolution two essential features of the adaptive immunity have been established: A) Development of a still larger variety of B- and T-cellreceptors B) According to the different living environments and lifecycles of pathogens a whole range of different effector mechanisms has developed If every host would quickly be killed after the infection by a pathogen, this would in the long term hardly be advantageous for the survival of the pathogen as its rapid demolition by the immune system, just before it could breed (Modus Vivendi). Monika Raulf 49
Disease agents can damage tissues in different ways Monika Raulf 50
For the immunity provide as well already available reactants as also the immunological memory T-cells and antibodies First immune reaction Protective immunity Immunological memory Day 1 to 42 Year 1 to 4 First infection Symptomless re-infection Easily proceeding or symptomless reinfection Monika Raulf 51
After the removal of the infection most of the effector cells die off (the antibody levels decrease in parallel) (negative feedback) and memory cells occur. Apoptosis of most of the effector cells. Nevertheless, some cells survive and deliver the raw material for memory cells and the reactions of the B-cells Immunological memory = Ability of the immune system, to react quickly and effectively on disease agents, which it met before already (u.a. vaccine protection) Monika Raulf 52
Immunological memory Is most probable maintained by long-lasting antigen specific lymphocytes, which are activated by the first contact and remain alive, until they meet the pathogen for a second time. It is assumed that most of the memory cells are in an inactive stage, but a small percentage on particular dates undergoes a division; IL-15 could be a stimulus. T-memory cells have different surface proteins than armed T-effector cells (e.g. they don t express CD69, but abundances of the protein Bcl-2, which facilitates the survival of the cell, the concentration of CD44 on the surface increases) CD4-cells can differ into two sorts of memory cells: a) Effector-memory cell (CCR7-neg.), b) Central memory cell (CCR7-pos) Monika Raulf 53