T1 L14 regulating immunological responses - role of cytokines and chemokines 28.4.23 DT (1).pptx

Regulating immune responses: the role of cytokines (and chemokines) BSMS Module 204 Daniela Teixeira 28-04-2023 Your learning outcomes: Be able to: • explain the basic classification and terminology, role and functions of cytokines and their sub-family, called chemokines, in coordinating immune re...

Regulating immune responses: the role of cytokines (and chemokines) BSMS Module 204 Daniela Teixeira 28-04-2023 Your learning outcomes: Be able to: • explain the basic classification and terminology, role and functions of cytokines and their sub-family, called chemokines, in coordinating immune responses • give examples with respect to some mechanisms • • • • • Cell differentiation and haematopoiesis Inflammation/wound healing Host defence Hypersensitivity Diagnostic/therapeutic use Cytokines – general information Cytokines: secreted proteins responsible for the interaction between cells of the immune system with one another and with other host cells • Interactions are essential during both the innate and adaptive immune responses • Promotion of growth and differentiation of immune cells • Activation of lymphocytes and phagocytes to eliminate microbes • Stimulation of movement of immune cells from blood into tissues and within tissues • Chemokines: large subset of structurally related cytokines regulation of cell adhesion and migration • They can be manufactured in the laboratory and used as medicines to help the body fight cancer, infections, and other diseases • Immunological diseases: the most effective drugs target cytokines Cytokines – general information Cytokines: secreted proteins responsible for the interaction between cells of the immune system with one another and with other host cells • Examples are interleukins, interferons, and colony-stimulating factors • Some cytokines stimulate the immune system and others slow it down • They may be pro- and anti-inflammatory • They may be made by many or only by a few cell-types • They may be also made by non-immune cells (endothelial and epithelial cells) • They may have effects on many or just a few cell-types/tissues Cytokine action mode: autocrine, paracrine, endocrine Autocrine (same cell) Endocrine (distant) Via circulation Secreted cytokine Paracrine (close by) Cytokine action mode: autocrine, paracrine, endocrine Example: biologic actions of IL-2 • Autocrine: stimulates the survival, proliferation and differentiation of T lymphocytes • Paracrine: promotes the survival and proliferation of regulatory T cells Cellular And Molecular Immunology, Tenth Edition Cytokine ‘pleiotropy’ and ‘redundancy’ Cytokines may act on a few or many tissues, may have unique or redundant effects • Cytokine pleiotropy – the higher pleiotropy the more cell types or tissues are targeted • Cytokine redundancy – the fact that different cytokines may have the same effects This is also true for their receptors • Cytokine receptor pleiotropy – various cell types and tissues express the same receptor • Cytokine receptor redundancy – different cytokines receptors may mediate the same effects in response to some cytokines Actions: pleiotropy e higher pleiotropy, the more cell types or tissues are targeted IL-4 B-cell -> class switch to IgE T-cell -> Th2 differentiation CD4 Th cell Actions: synergy fferent cytokines have the same effects on the same cell or tissue ytokines produced by the same cell or by different cells) IL-4 B-cell -> class switch to IgE Induced by IL-4 and IL-13 CD4 Th cell Mast cell IL-13 Both make IL-4 and IL-13 T-cell -> Th2 differentiation Actions: antagonism nt cytokines have the opposite effect on the same cell or tissue nes produced by different cells, or by the same cell in different moments => modulation of resp CD4 Th cell IL4 CD4 Th cell IFN-g B-cell -> class switch to IgE B-cell -> class switch to IgG1 Cytokines and their receptors • Act on their target cells by binding to specific membrane receptors • Receptors mediate the effect of the cytokine into the cell • The distribution of cytokine receptors determines whether or not cytokines have an effect on other cell types and tissues • Receptors are classified in different families based on conserved extracellular cytokine-binding domains and shared intracellular signalling mechanisms Representative cytokines or other ligands that bind to each receptor family are listed below the schematic drawings. Picture extracted from Cellular And Molecular Immunology, Tenth Edition. Cytokines and their receptors Cytokine receptors often have several chains, or ‘subunits’: generally 1 – 3 subunits Some chains are shared between different receptors: ‘common chains’ Groups of cytokine receptors share identical or highly homologous subunit chains. Picture extracted from Cellular And Molecular Immunology, Tenth Edition. Cytokine receptors: shared receptor chains Diversity of shared receptor-receptor interactions: Shared cytokine receptor γ chain and its various receptor partners are depicted These complexes are formed by the combination of ligand-specific α and/or β receptors with shared cytokine receptors (Abbreviations: TSLPR, thymic stromal-derived lymphopoietin receptor.) Annu Rev Immunol. 2009 ; 27: 29–60. Cytokine signalling Engagement of signal transduction pathways • Type I and type II receptor families signalling pathway • Tyrosine kinases: Janus kinases (JAKs), attached to the cytoplasmic domains of the receptor • Transcription factors: signal transducers and activators of transcription (STATs) • Binding of cytokine: receptor molecules are brought together • Activation of JAKs: tyrosine phosphorylation of signalling proteins, such as cytosolic STATs. • STATs form dimers that migrate to the nucleus and bind to specific DNA sequences • Activation of transcription of cytokineresponsive genes Negative regulation by other ligands or cytokines themselves: • Induction of suppressors of cytokine signalling Cytokine and the generation of Th1 CD4 Th2 effector T cells Cytokines: Th17 Antigen presenting cells: produce cytokines, which induce differentiation of naïve CD4 T cells into subsets of helper T cells Other cells: NK, mast cells Effector CD4 T cells: Action through secreted cytokines Cytokines increase its own development and inhibit the development of other subsets Differentiation: Governed by transcription factors that promote gene expression in the T cells with stable commitment to a particular subset Pictures extracted from Cellular And Molecular Immunology, Th1 cytokines and their roles Stimulated mainly by pathogens ingested by phagocytosis, intracellular pathogens Induced by IL-12 and IFNg from DC, macrophages and NK (innate immunity) Main function: eliminate intracellular infections, mainly through activation of macrophages Signature cytokines: IFNg IFNg: Induction of more Th1 differentiation: activation of APCs to produce IL-12 Amplification of inflammation: Activation of macrophages, DCs and other cells to produce TNF, IL-1 and chemokines Inhibition of differentiation of naïve T cell into Th2 and Th17 subsets Activation of macrophages to kill phagocytosed pathogens Enhancement of antigen presentation process (costimulatory molecules on APCs) TNF: Mediator of the acute inflammatory response to bacteria and other infectious pathogens Activation of endothelial cells and neutrophils Pathologic role: Tissue injury caused by activated macrophages and neutrophils (chronic inflammatory diseases, autoimmune diseases) Picture extracted from Cellular And Molecular Immunology, Tenth Edition. Th2 cytokines and their roles Response to helminths and allergens Induced by IL-4 (activated T cells, mast cells) Induced by cytokines produced by damaged epithelium (IL-25, IL-33) Main function: Eradicate helminthic infections: stimulation of reactions mediated by IgE, mast cells and eosinophils Promote tissue repair: alternative macrophage activation Inhibited by IFNg Signature cytokines: IL-4, IL-5 and IL-13 IL-13 IL-4 Stimulates differentiation of T naïve to Th2 Increases mucus secretion from airway and gut epithelial cells (+ IL-13) Class switching to IgE: activation of mast cells (+ IL-13) Alternative activation of macrophages (+ IL-13) Stimulates intestinal peristalsis IL-5 Stimulate growth and differentiation of eosinophils Activates mature eosinophils: release their granules (+ IL-13) Stimulates the recruitment of eosinophilscontents Pathologic role: central to the development of atopic diseases (allergy, asthma) Picture extracted from Cellular And Molecular Immunology, Tenth Edition. Th17 cytokines and their roles Stimulated mainly by extracellular bacteria and fungi Induced by IL-1, IL-6 and IL-23 from DC and macrophages (innate immunity) Main function: eliminate pathogens recruiting neutrophils, and repair injured epithelial layers Inhibited by IFNg and IL-4 Signature cytokines: IL-17 and IL-22 IL-17 Induces neutrophil-rich inflammation by stimulating the production of proinflammatory cytokines (TNF, IL-1, IL-6) and chemokines Neutrophils phagocyte and destroy bacteria and fungi Stimulates the production of antimicrobial substances (defensis) IL-22 Produced by Th17 cells in epithelial tissues (skin and gastrointestinal tract) Maintains epithelial integrity: Stimulates the production of antimicrobial substances Stimulates repair reactions: promotes barrier function of epithelia Pathologic role: significant contribution to tissue damage in autoimmune diseases Picture extracted from Cellular And Molecular Immunology, Tenth Edition. IL-2: Produced by conventional T cells responding to self or foreign antigens Acts on regulatory T cells Promotes the survival and function of the Tregs Cytokines and their roles IL-2: Proliferating CD4 cell Naive CD4 TGF-beta + IL-1 and IL-6: Promotes the development of the Th17 subset => Opposing actions depending on the context: ability to suppress immune and inflammatory responses (Tregs) or ability to promote the development of proinflammatory Th17 cells IL-1, IL-6, TGF-beta Th0 Tregs produce IL-10 and TGF-beta: control the responses of the conventional T cells => Immune regulation IL-2, TGF-beta Treg Th17 IFN-g, IL-12 IL-4 IL-17 IL-22 Th1 TNF IFN-g Th2 IL-4, IL-5, IL-13 TGF-beta IL-10 TGF-beta: Stimulates the development of peripheral Tregs Inhibits the proliferation and effector functions of T cells: Th1 and Th2 subsets Inhibits classical activation of macrophages IL-10: Inhibits the production of IL-12 by activated DCs and macrophages: inhibition of IFN-γ production. Inhibits the expression of costimulatory molecules on DCs and macrophages: termination of cell-mediated immune Cytokines and their roles Different stimuli activate tissue macrophages to develop into functionally distinct populations: Classic macrophage activation: • Induced by microbial products and IFNg • Results in potent microbicidal functions and inflammation Alternative macrophage activation: • Induced by IL-4 and IL-13 (Th2 cells) • Macrophages produce IL-10 and TGF-beta • IL-10: termination of cell-mediated immune reactions • TGF-beta: control of inflammation • Induction of tissue repair and fibrosis (stimulation of collagen synthesis and angiogenesis) • Pathologic role: diseases in which fibrosis is an important component (pulmonary fibrosis and systemic sclerosis) Th2 cytokines also suppress classical macrophage activation Classical and alternative macrophage activation. NO, Nitric oxide; ROS, reactive oxygen species. Picture extracted from Cellular And Molecular Immunology, Tenth Edition. Chemokines – general information Chemokines: a sub-family of cytokines - chemotactic cytokines. • A large family of small, secreted (sometimes immobilised) proteins that signal through cell surface G protein-coupled chemokine receptors • Stimulate the migration of cells, most notably white blood cells (leukocytes) • Play a central role in the development and homeostasis of the immune system (e.g. homing, anatomic immune cell distribution) • May act inducing Chemotaxis (migration following a gradient of increasing concentration of chemokines) Haptotaxis (migration following a gradient of increasing concentration of immobilised molecules) Chemokine: structure-based names • Small size (8-14 kDA) • Produced in large amounts (to create concentration gradients) • Contains usually 4 cysteines in conserved positions (provide tertiary structure) • Spacing between the first and second determines the type/name: C, CC, CXC, CX3C Chemokines and receptors Chemokine: + L (ligand) Chemokine receptors: + R (receptor) C Family (XCL1) C Family (XCR1) CC Family (CCL1) CC Family (CCR7) CXC Family (CXCL) CXC Family (CXCR4) CX3C Family (CX3C1) CX3C Family (CX3CR1) G protein-coupled chemokine receptors Note: respective Ligand and Receptor usually do not correspond to the same identifier Examples: CCL25 interacts with CCR9 CCL21 interacts with CCR7 CXCL13 interacts with CXCR5 Chemokine actions Steps mediating leukocyte recruitment into tissues 1. Production of cytokines at site of infection and tissue injury Macrophages (or DCs and other cells) encounter microbes in extravascular tissue: activation and secretion of cytokines (TNF and IL-1) and chemokines Cytokines stimulate endothelial cells to express adhesion molecules (selectins) 2. Selectin-mediated rolling of leukocytes Blood vessels dilate and blood flow slows Leukocytes move closer to the vessel lining Interaction of selectin ligands expressed by leukocytes to selectins induced on endothelial cells Rolling: process due to the low affinity of these molecules 3. Increase in integrin affinity Chemokines displayed on endothelial cells bind to their receptors on the rolling leukocytes Integrin (on leukocytes) change to a high-affinity state Endothelial cells lining postcapillary venules at the site of infection. Leukocyte-endothelial interactions mediating leukocyte recruitment into tissues. Picture extracted from Cellular And Molecular Immunology, Tenth Edition. 4. Integrin-mediated firm attachment of leukocyte to endothelium 5. Transmigration of leukocytes through endothelium (diapedesis) 6. Migration of leukocytes to site of infection and tissue injury Movement into the tissue towards the cytokine gradient Chemokine actions Chemokines are involved in the anatomic organization of lymphoid organs and regulate the traffic of leukocytes through different regions of secondary lymphoid tissues • Constitutive expression to maintain normal tissue architecture • Expression induced under inflammatory conditions: leukocyte migration out of blood vessels into tissues Distinct areas of B and T lymphocytes in the node • T cell zone • B cell zone (follicle) Specialized cells located in each area secrete the chemokines • T cell zone: fibroblastic reticular cells (FRCs) • B cell zone: FRCs and follicular dendritic cells (FDCs) The schematic diagram illustrates the path by which naive T and B lymphocytes migrate to different areas of a lymph node. Picture extracted from Cellular And Molecular Immunology, Chemokine actions Naïve lymphocytes enter the node through an artery, leave the circulation, and migrate to different zones Naïve T cells express CCR7 that binds CCL19 and CCL21 produced by T cell zone FRCs: Chemokines promote the movement of T cells from blood into the T cell zone Naïve B cells express low levels of CCR7, but high levels of CXCR5, that binds CXCL13 produced by B cell zone FRCs and FDCs: DCs (activated by microbes) express CCR7 and lymphatic endothelial cells express CCL21: Circulating naïve B cells enter lymph nodes and are attracted into the follicles (FDC: appropriate APC for B cell) DCs enter the node through afferent lymphatic vessels and migrate to the same area as do naïve T cells (DC: appropriate APC for T cell) The schematic diagram illustrates the path by which naive T and B lymphocytes migrate to different areas of a lymph node. Picture extracted from Cellular And Molecular Immunology, FRCs = fibroblastic reticular cells FDCs = and follicular dendritic cells (FDCs) Cytokine storm Cytokines may act on cells or tissues and induce • The production of the same or other cytokines, triggering a cascade • The up- or downregulation of receptors for other cytokines • Many stromal cells can produce cytokines: endothelial cells can produce IL-6, causing inflammatory cells to be activated, fever and acute phase protein production in the liver • Severe infections caused by influenza virus (H1N1 and H5N1): hyperactive resistance of the host against the virus, resulting in an excessive inflammatory reaction called cytokine storm Image: Liu, Q., Zhou, Yh. & Yang, Zq. The cytokine storm of severe influenza and development of immunomodulatory therapy. Cell Mol Immunol 13, 3–10 (2016). Cytokine storm 1. Infection of respiratory epithelial cells (primary target for influenza virus): • • • • Recruitment of inflammatory cells Increase of tissue damage, inflammatory and antiviral stimuli => Amplification of cytokine storm Death of cells: tissue damage Infection of other cells as alveolar macrophages => acute inflammatory response: tissue damage and activation of pro-inflammatory cytokines or chemokines 2. Cytokine/chemokine-activated macrophages and infected dendritic cells: • 3. Acute inflammation enhanced by cytokines/chemokines: Release of more cytokines and chemokines => Enhancement of the acute inflammation: start of cytokine storm Virus clearance and Initiation of regenerative processes and resolution of the damage OR Severe inflammation associated with cytokine storm => Persistent organ dysfunction (diffuse alveolar damage) Systemic cytokine storms: Cytokines/chemokines into the circulation => Multi-organ dysfunction Image: Liu, Q., Zhou, Yh. & Yang, Zq. The cytokine storm of severe influenza and development of immunomodulatory therapy. Cell Mol Immunol 13, 3–10 (2016). https://doi.org/10.1038/cmi.2015.74 Considerations: Host susceptibility Virus Cytokine in therapeutic use: Therapeutic use of cytokines IL-10: Psoriasis IFN-alpha: viral hepatitis Cytokine antagonists in therapeutic use: Anti-TNF: rheumatoid arthritis Offer higher clinical response rates and improved chances of achieving clinical remission RA, Crohn’s disease RA Psoriasis Hypereosinophil ic syndrome RA Asthma RA, Crohn’s disease, psoriasis, psoriatic arthritis Kopf, M., Bachmann, M. & Marsland, B. Averting inflammation by targeting the cytokine environment. Nat Rev Drug Discov 9, 703–718 (2010). https://doi.org/10.1038/nrd2805 Summary • Cytokines are a family of protein molecules made by certain immune and non-immune cells. • They have effects on the immune system and on many other cells and tissues. • Cytokines may act in an autocrine, paracrine and endocrine fashion • Cytokines may act in synergy, or antagonise each other • They act through specific receptors constituted by of 1 – 3 subunits, and receptor subunits may be shared • The action of cytokines are mediated through engagement of signal transduction pathways, with the involvement of tyrosine kinases (JAKs) and transcription factors (STATs) • The action of cytokines can cause significant pathology: cytokine storm, autoimmune diseases, allergic diseases • Cytokines are therapeutics as well as therapeutic targets Summary • Chemokines are a sub-family of cytokines. • They are small, secreted proteins that signal through cell surface G protein-coupled chemokine receptors. • Four main families: C, CC, CXC, and CX3C (CXXXC) • They induce chemotaxis when soluble, and haptotaxis when immobilised • They are often made in large amounts to provide concentration gradients • They stimulate the migration of mostly white blood cells to tissues • They are important for the development of the immune system, ‘homing’ and anatomic organization of lymphoid organs • Like cytokines they are involved in both protective and destructive processes Thank you! 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