MIID 2024 Lecture 10: Inflammation and the Immune System PDF

MIID 2024 Lecture 10 Inflammation and the immune system Andrea Bottaro  CMSRU Disclosure In accordance with the ACCME Essentials and Standards, everyone involved in planning and presenting this CMSRU educational lecture has no relevant commercial relatio...

MIID 2024 Lecture 10 Inflammation and the immune system Andrea Bottaro  CMSRU Disclosure In accordance with the ACCME Essentials and Standards, everyone involved in planning and presenting this CMSRU educational lecture has no relevant commercial relationships or conflicts of interest. There is no commercial support for this program. 1 Instructional materials contained in this slide set may include copyrighted material. The copyright law of the U.S. (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Please do not reproduce, or transmit, any portion of this content. This session will cover: General properties of acute inflammation (functions, cell types involved, onset and resolution) from an immunological standpoint Details of the process of immune cell recruitment to inflamed tissues Key inflammatory factors and their functions: - inflammasomes; - major inflammatory cytokines (IL1β, IL6, TNF); - histamine; - eicosanoids; - ROS and NO. An introduction to immunological hypersensitivities The mechanisms of resolution of inflammatory reactions 3 Functions of acute inflammation: - Destroy (invading organisms) - Dispose (of dead tissue/cells, dead pathogens) - Dilute (toxins, pro-inflammatory mediators and toxic inflammatory effector molecules) - Develop (prepare tissue for repair and healing) - Deter (prime the immune response) The immune system is the primary effector of the onset, regulation and resolution of inflammatory processes, and inflammation is essential for the development of normal immune responses 4 Inflammation has an extended cast of characters: - Vascular endothelial cells and the vascular basement membrane (collagen, proteoglycans, laminin) - Tissue and organ cells: specialized tissue cells (eg, epithelial clels, osteoblasts, hepatocytes) and connective tissue cells (fibroblasts, other stromal cells), and the extracellular matrix (collagen, fibronectin, elastin) - Tissue-resident immune system cells (mast cells, macrophages and their various subsets, dendritic cells, lymphocytes) - Circulating leukocytes (neutrophils, monocytes, lymphocytes, eosinophils, basophils, platelets) (and possibly, based on recent evidence – erythrocytes) - Inflammatory mediators: cytokines, neuropeptides, chemical mediators (lipid mediators, histamine, ROS, complement, clotting factors) 5  Sequential regulation of the onset, progression and resolution of acute inflammation Prostaglandins Pro-resolution factors: Leukotrienes TGFβ, IL10, eicosanoids PAF (eg, resolvins, maresins) Growth factors Resident cells: Neutrophils Induced M2 macrophages, macrophages, DCs, macrophages (T-regs) mast cells, (NK, ILCs) (from monocytes) Lawrence T, Nat Rev Immunol 2, 787, 2002 (adapted) Cain JA, Nat Rev Immunol 17, 233, 2017 (adapted) 6 What types of signals can initiate an inflammatory response? 7 Pathogen Innate immunity and the acute inflammatory response fib. V Y V MΦ DC Mast Cell  Pathogen Innate immunity and the acute WBC production inflammatory (GM-CSF, TNF…) response V To lymph Y V fib. nodes Y MΦ DC IL4 MΦ IL13 Mast Phagocytosis, Cell Antimicrobials, IL12 ROS, NETs, Infl. Cytokines, IFNγ mediators Histamine Chemokines (ROS, Cytokines Enzymes… PGs, NO) (IL1,TNF, Th1 IL8 IL6 …) Chemokines Ly Repair factors (PDGF, TGFβ) Ly  Early signals determine type of innate cells recruited, DC maturation pathways, and ultimately adaptive responses Prototypical adaptive Pathogen and early response immune signals Responses to viruses, intracellular bacteria “Type 1 inflammation” Regulatory, tolerogenic responses Anti-inflammatory Responses to parasites “Type 2 inflammation” IL4 Kapsenberg, Nat Rev IL6, TGFβ Responses to Immunol 3, 984, 2003 Type 17 PAMPS and TFs extracellular IL22 (modified) IL23 TH17 bacteria, fungi IL17 IL17 IL23 “Type3 IL23 inflammation” Leukocytes extravasation into inflamed tissues is a highly regulated, stepwise process Eg: VLA4 LFA1 (Diapedesis) Eg: PECAM1 ICAM1 (eg: ICAM1 VCAM1 VCAM1) 11  Leukocyte adhesion and extravasation require induction of conformational changes in surface integrins Adapted from Salmi M and Tohka S, Essential Cell Biology, 3rd Ed, Garland. Leukocyte adhesion deficiencies are associated with defects in the extravasation process, leading to immune deficiency and extremely high WBC counts: LAD1: lack of LFA1 integrin β chain (CD18) expression. LAD2: glycosylation defect - absence of selectin ligands. LAD3: defect of induction of high-affinity integrins 12 Main classes of inflammatory mediators Neurotransmitters and neuropeptides Histamine (NPY, SP, serotonin, ACh…) Cytokines (IL1, NO TNF, IL6, IFNs, ROS INFLAMMATION IL17, etc); chemokines Lipid mediators Activated complement and (prostaglandins, clotting cascade components leukotrienes, and related plasma proteins thromboxanes, PAF) (eg, C3a, C5a , bradykinin, thrombin, …) 13 The early acute inflammation cytokine triad: IL1β, TNF, IL6 - local and systemic effects Fever (hypothalamus) Endothelial IL1β cell activation (edema, extravasation) TNF Neutrophil production, mobilization IL6 (bone marrow) Acute phase protein production (liver) Leukocyte activation, differentiation ? 14 Name some acute phase proteins that you have already learned about. 15 The cytokine triad in early acute inflammation: IL1β, TNF, IL6 - Local and systemic effects Fever IL6 IFNγ (hypothalamus) TNF IL8 IL1β Endothelial IL1β cell activation (edema, IL10 IL2 extravasation) TNF Dysregulated amplification: Neutrophil production, “cytokine storm” mobilization reaction, a form of IL6 (bone marrow) systemic inflammatory reaction syndrome Acute phase protein (SIRS) production (liver) Leukocyte activation, differentiation 16 IL1β production is driven by “inflammasomes” : cytosolic inducible complexes in immune system cells, epithelial cells (+ others) Components: a PRR (eg, NLRs, AIM2, pyrin), adaptor proteins, caspase 1 integrate signals from PAMPs, DAMPs and certain environmental inducers, as well as other PRRs activate inflammatory cascades (IL1β, IL18 secretion, inflammatory cell death - pyroptosis) NOD-like receptors (NLR) involved in common diseases (a type of PRR) DAMPs and chemical PAMPs signals atherosclerosis gout, pseudo-gout Urea, CaPP crystals Type 2 diabetes Adapted from: Davis, Annu Rev Alzheimer’s Immunol 29, 707, 2011 Pulmonary disease 2. processing by 1. pro-cytokine synthesis caspase 1 TLR signals pro-IL1β Casp-1 IL1β 3. Secretion of (+ others) pro-IL18 IL18 functional cytokines 17 Mutations in inflammasome components/regulators -> hereditary autoinflammatory syndromes Recurrent spontaneous episodes of sterile inflammation: Fever, arthritis, skin rashes, sterile peritonitis/pleuritis, etc. FMF (familial Mediterranean fever): AR Pyrin gene mutations: Most common in patients of Armenian/Turkish/Jewish descent CAPS (cryopyrin-associated periodic syndromes) – AD NLRP3 gene defects: several diseases, diverse clinical manifestations of variable severity, depending on mutations Familial Mediterranean Fever Familial Cold Auto-inflammatory Syndrome, Muckle-Wells Syndrome Neonatal Onset Multisystem 18 Inflammatory Disease  Non-hereditary forms of inflammasome-linked diseases: adult-onset Still’s disease and systemic juvenile idiopathic arthritis Similar presentation: fever, myalgia, inflammatory arthritis, pleuritis/ pericarditis, organomegaly Spoiler: she has AOSD! Jung JY, Front Immunol 11:583513, 2020 Probably due to TLR triggering by DAMPs -> inflammasome activation -> IL1β Canakinumab (anti-IL1β) approved by FDA in 2020 for AOSD treatment. 19  Which of the following PAMPs is a ligand for the TLR4 receptor? A. Flagellin B. dsRNA C. CpG DNA D. LPS E. ssRNA 20  Toll-like receptors (TLRs) - prototypical PRRs Membrane receptors; 9 different activating types (+ 1 “suppressor” receptor) Widely expressed (innate immune system, but also adaptive immune system and other cell types) Some on the cell surface, others on intracellular vesicles (endosomes). Recognize a wide array of PAMPs, some DAMPs. TLR4 bound to LPS and co-receptors -> Abbas, Cellular & Molecular Immunology, 10th Ed Tumor necrosis factor (TNF): secreted by macrophages, Th1 cells, others highly pleiotropic (many activities on many cell types) Key cytokine in chronic inflammatory autoimmune diseases: RA, Crohn’s, psoriasis, 8 months etc Dysregulated expression of TNF in transgenic mice is sufficient to induce chronic, progressive inflammatory-erosive arthritis similar to human RA (Keffer, 1991) TNF is part of a large family (TNF superfamily) of proteins that can be mounted on the cell membrane or secreted by enzymatic “shedding”. Important biological functions in health and disease. Equally large number of receptors (TNFR superfamily). 23  IL6: many functions in normal immunity Secreted by: monocytes/MΦs, and disease T cells, other cell types Signaling “in trans” (many cell types): via Classical shed receptor (eg, by signaling neutrophils) -> “ Rose-John S, Nat Rev Rheum 13, 399, 2017 (adapted) Role in acute and chronic inflammatory responses: cytokine storms/systemic inflammatory response syndrome; acute phase response; autoimmune diseases (RA, Crohn’s disease,…); adaptive immune responses; cancer/ lymphoproliferative disorders (eg, Castleman disease), etc. 24  Cytokine antagonists are commonly used as therapeutic agents, eg: - TNF inhibitors: several types, eg: etanercept (soluble TNF receptor), infliximab and adalimumab (anti-TNF antibodies) - widely used for many autoimmune/inflammatory diseases (RA, psoriasis, IBD, etc…) - Anti-IL1 agents (eg, canakinumab and anakinra, a recombinant antagonist, IL1RA): autoinflammatory syndromes, refractory moderate to severe RA - IL6 antagonists (eg, tocilizumab, anti-IL6 receptor; others): RA, some forms of vasculitis, “cytokine storm”-like reactions Anti-TNF agents have revolutionized treatment of inflammatory autoimmune diseases in the last ~20 years Chaudhari K, Nat Rev Drug Disc 15, 305–306 (2016) 25 Neurotransmitters Histamine: related to the aa Histidine decarboxylase histidine, recognized by G-protein-coupled receptors (H1-4), with both peripheral and CNS activity. Sleep-wake cycles Hypothalamus Vasodilation, vascular regulation permeability, Appetite control Pain modulation bronchoconstriction, pain/itching. Serotonin: tryptophan derivative. Role in inflammation mainly in pain response, vascular permeability. Bradykinin: product of “contact activation cascade” (side branch of intrinsic coagulation pathway). Vasodilation, vascular permeability, pain, bronchoconstriction (in asthma). 26  H1 antagonists: allergy meds, Peripheral: pain, itching “antihistamines” (1st gen: drowsiness Central: nausea, from CNS effects) headache… H2 blockers: stomach acid secretion Vascular inhibitors (acid reducers) permeability, Gastric Stomach edema, Nervous parietal acid congestion system cells secretion H1-4 H2 Endothel Histamine & H1 Lymphocyt ia H1,2 (2,4) es inflammatio n Mucus H1 H1(-4) secretion, Mucosa H1,2 Inflammatory Other congestio e Smoot mediator immune n h production, syst. muscle chemotaxis, cells (H1) B/T cell (H1,2) function, Bronchoconstriction Vasodilation hematopoiesis (capillaries) 27 Lipid mediators (eicosanoids): major biosynthetic pathways and key enzymes (phospholipase A2, cyclooxygenases, 5-lipoxygenase) (Review your notes from lectures on lipids for details on eicosanoid biosynthesis) Resolvins acCOX-2 Maresins PAF omega-3 FA 5-LOX Protectins P450 pathway acCOX-2 5-LOX Lipoxins Prostaglandins TXB2 Wang D, Nat Thromboxanes Rev Cancer 10, 181, 2010 (modified) Leukotrienes acCOX-2 = acetylated COX2 (eg, by aspirin) Pro-inflammatory (mostly): prostaglandins, leukotrienes, thromboxanes; PAF Anti-inflammatory: resolvins, maresins, protectins, lipoxins 28  Nitric oxide as a mediator of inflammatory responses Inflammatory signals (TNF, Constitutive IL1β, IFNγ, IL6, etc), PAMPs, … nNOS - neural eNOS - endothelial iNOS - inducible NFκB nNOS - neural: Vascular tone (many cell types, including neurotransmission Smooth muscle cell proliferation MΦs, neutrophils and other pain signals Inhibits platelet aggregation phagocytes, T cells, fibroblasts, endothelial cells, etc): Antimicrobial activity Cytotoxicity NOS Vasodilation NO Vascular permeability Pro-inflamm. cytokine induction but also L-Arginine L-Citrulline Tissue repair, healing (M2 MΦs) Anti-inflammatory cytokine regulation 29  ROS in innate immunity and inflammation Phagocytes (cell membrane, Cell damage (eg, phagosomes) NADPH oxidase necrosis) mitochondrial 5-LO OXPHOS Injury inducible nitric Inflammation oxide synthase (iNOS) superoxide detox enzymes H2O peroxynitrite hydrogen O2 peroxide MP O+ Protein Cl - nitration Signaling (gene Oxidative expression) HOCl- stress Injury hypochlorous Injury Inflammation radical Inflammation CAT: catalase Antimicrobial SOD: superoxide dismutase activity MPO: myeloperoxidase 30 GPX: Glutathione peroxidase  Acute inflammation factors and functions Mechanism Mediators Vascular permeability, edema Histamine; LT-C4/D4/E4 (“cysteinyl-LTs”); (“tumor”) complement (C3a, C5a); NO; Serotonin; VEGF; TNF Vasodilation (“rubor”, “calor”) PGE2/D2; Histamine; NO; VEGF Vasoconstriction TxA2; LT-C4/-D4 Bronchoconstriction (asthma) Cysteinyl-LTs; TxA2; PGD2; Histamine Endothelial activation; leukocyte IL1; TNF; C5a; IL8/chemokines; LT-B4; adhesion, chemotaxis, extravasation Histamine Pain (“dolor”) Bradykinin; PGE2; Substance P; Histamine; TNF; serotonin Fever IL1; IL6; TNF; PGE2 Tissue damage (“functio laesa”) ROS; Leukocyte-secreted enzymes (collagenase, elastase, other proteases…) Acute phase response (liver) IL6, TNF, IL1 31  Inflammation leads to “reactive” draining lymph nodes (lymphadenopathy) enlargement, expansion of lymphatic sinusoids, increased recruitment/ retention of lymphocytes (for immune response). Formation of secondary follicles and germinal centers Adapted from Drayton, Nat Immunol Non-lymphoid 7:344-53. 2006 tissues (pancreas, joints, liver, etc) 32 Inflammatory reactions can also be initiated by adaptive immune responses to specific antigens - Typically memory responses (require prior antigen exposure, or “sensitization”) - Can be mediated by antibodies, or by T cells - Exaggerated, pathological responses directed toward harmless or self antigens are called “immunological hypersensitivity reactions” - Associated with many immunopathological conditions: allergies, autoimmune diseases, drug and transfusion reactions, transplant rejection,… allergens autoantigens microbial antigens 33 Inflammatory reactions in response to harmless antigens are immunological hypersensitivities (Gell-Coombs classification) Antibody-mediated (Types 1-3) T cell-mediated (Type 4) 34 Resolution of inflammation occurs via removal of initiating signals, as well as active mechanisms Apoptotic neutrophils recruit and promote differentiation of pro-resolution (M2) MΦs, -> clearance of Removal of dead cells (“efferocytosis”) dead cells and tissue, generation of resolvins, maresins, lipoxins and other anti-inflammatory mediators (TGFβ, IL10, NO…). “Resolving exudate”: pus bonum et laudabile 35 Soehnlein O Nat Rev Immunol 10, 427-439, 2010  “Appropriate” “Inappropriate” activation (eg, Inflammatory stimulus activation (e.g. pathogens, autoinflammation, trauma) Innate immune autoimmunity, response allergy) Adaptive immune response Self-amplifyin g Acute inflammation dysregulated feedback Clearance of loop Failure to clear inflammatory stimulus inflammatory stimulus, dead Clearance of damaged/dead cells cells/tissues (efferocytosis) SIRS, “Cytokine Failure of Active resolution storm” resolution mechanisms mechanisms (anti-inflammatory cytokines, resolvins, Chronic lipoxins, etc) inflammation Resolution 36 After this session, you should be able to: -Outline the physiological functions of inflammation and its integration with innate and adaptive immune responses -Describe the general process of acute inflammatory reactions, highlighting key cellular/molecular factors -Explain the mechanism of leukocyte recruitment and extravasation to inflamed sites, including the role of chemotaxis and key adhesion molecules (selectins, integrins); describe leukocyte adhesion deficiencies and their basis -Outline the general properties of the inflammasomes, and their link to hereditary autoinflammatory syndromes -List major types of inflammatory mediators and summarize their general functions and basic biosynthetic pathways. Focus on cytokines (IL1β, TNF, IL6); histamine; eicosanoids; nitric oxide; ROS. 37 - Link major inflammatory mediators to their specific effects on local and systemic manifestations of inflammation: edema, endothelial activation and leukocyte recruitment, vasodilation, vasoconstriction, bronchoconstriction, fever, and the acute phase response - Contrast the triggering mechanisms of inflammatory reactions initiated by innate signals to those initiated by antigens, and summarize how the latter can be categorized under the immunological hypersensitivity reactions classification. - Explain the significance of active resolution mechanisms of inflammation, including the role of signals like pro-resolution eicosanoids (lipoxins, resolvins) and regulatory cytokines (IL10, TGFβ), and of specialized cell populations (eg, M2 macrophages and T-reg cells) 38 Read more! Robbins and Cotran, Pathologic Basis of Disease, 8th Ed, Chapter 2, on ClinicalKey Abbas AM et al, Cellular and Molecular Immunology, 10th Ed, Elsevier, Ch. 4, 19 (selections), on ClinicalKey Dinarello CA, Anti-inflammatory Agents: Present and Future. Cell 140, 935-950, 2010 Kastner DL, et al, Autoinflammatory Disease Reloaded: A Clinical perspective. Cell 140, 784-790, 2010 39 Term suggestions for concept mapping: TNF Leukemoid Granulomas reaction Integrins Endothelium LADs ROS Macrophage CGD Neutrophil Chemokines Extravasation 40