INFLAMMATION ENTZUNDUNGEN ΔΕΙΤΕΕΠΙΣΗΣ 炎症えん- しょう 병리학교실조남훈
General Features of Inflammation Definition: A complex reaction to injurious agents ( microbes, necrotic cells ) in the vascularized tissue: vascular response, migration, activation of leukocytes and systemic reaction The inflammatory response is closely interwined with the process of repair regeneration / scarring Inflammation is fundamentally a protective response the ultimate goal of which is to rid the organism of both the initial cause of injury(eg.microbes, toxins) and the consequences of such injury(eg.necrotic cells and tissues)
TWO MAIN COMPONENTS OF INFLAMMATORY RESPONSE Vascular reaction & vs. Cellular reaction
Acute Inflammation (1) Def : Immediate and early response to an injurious agent rapid onset, short duration - exudation of fluid and plasma proteins - emigration of leukocytes (neutrophils) Stimuli for acute inflammation : Infection & microbial toxins / trauma / physical and chemical agents / tissue necrosis / foreign body / immune reactions Three major components of acute inflammation 1. Alterations in vascular caliber an increase in blood flow 2. Structural changes in the microvasculature the plasma proteins and leukocytes to leave the circulation 3. Emigration of the leukocytes from the microcirculation/ accumulation in the focus of injury, and their activation to eliminate the offending agents
Acute Inflammation (2) Exudation: escape of fluid, proteins and blood cells from the vascular system into interstitium or body cavity Exudate: inflammatory extravascular fluid with high protein concentration, cellular debris, specific gravity >1.020 due to increased permeability of small blood vessels Transudate: fluid with low protein content, sg <1.012 (mostly albumin) due to osmotic/hydrostatic imbalance without increase in vascular permeability Edema: excess fluid in the interstitial or serous cavity, whether exudate or transudate Pus: inflammatory exudate rich in leukocytes(mostly neutrophils), debris, and microbes
Formation of transudates and exudates 32mmHg in arteriolar end 12mmHg in venular end 25mmHg in mean tissue OP
Vascular Changes Changes in vascular flow and caliber 1. Vasodilation of the arterioles by histamine, NO effects on vascular smooth muscle blood flow heat, redness Earliest manifestation 2. Permeability of the microvasculature (vascular leakage) affecting venule with unaffected arteriole and capillary mediator receptor concentrated in venule most leukocytes around venules histamine, bradykinin, leukotrine. transient and short-lived 3. Exudation with vascular stasis 4. Leukocytes accumulate along the endothelium.
Mechanisms of Increased vascular permeability (Vascular leakage) 1. Formation of endothelial gaps in venules a. Immediate transient response-histamin-induced endothelial contraction (15-30 min) b. cytoskeleton skeletal reorganization of ec by IL-1, TNF, IFN-γ - delayed (2-12h) and long-lived (>1d) - endothelial contraction and separation of intercellular junction 2. Direct endothelial injury --- endothelial necrosis, detachment neutrophil adhere to endothelium immediate sustained response (immediately ~ several hrs until thrombosed or repaired) all levels of microcirculation affected
3. Delayed prolonged leakage : sunburn, UV, X-radiation - 2-12 hrs or more than 1d delayed - venule, capillaries - delayed e.c. damage (apoptosis) or cytokine 4. Increased transcytosis across channels-vegf-induced vesicovacuolar organelle 5. Leukocyte-mediated endothelial injury - leukocyte activation to release ROS, proteolytic enzymes - pulmonary/glomerular venule injury in ac inflammation 6. Leakage from new blood vessels: angiogenesis during repair
Principal mechanisms of increased vascular permeability in inflammation, New edition
Cellular Events: Leukocyte Extravasation Extravasation of leukocytes -sequential events in the journey of leukocytes from the lumen to the interstitial tissue 1. Margination ( 변연화 ), rolling ( 구르기 )and adhesion ( 유착 ) 2. Transmigration ( 유출 ) across the endothelium (diapedesis) 3. Migration in the interstitial tissues toward chemotactic stimuli
Adhesion and Transmigration (1) Endothelial/leukocyte adhesion molecules 1. Selectin: E-selectin in endothelium P-selectin in endothelium and platelets L-selectin in leukocyte types -GlyCAM-1, CD34 2. Immunoglobulin family molecules ICAM-1 (intercellular adhesion molecule 1) VCAM-1 (vascular cell adhesion molecule 1) PECAM (CD31) -interact with integrin on leukocytes 3. Integrin : transmembrane-adhesive heterodimeric glycoproteins, - bind to ICAM-1, VCAM-1 4. Mucin-like glycoprotein heparan sulfate binding to CD44
Selectins All function in adhesion of leukocytes to endothelial cells 3 family in different location Fast-on rate, fast off rate, low affinity binding Initial attachement and subsequent rolling of leukocytes L-selctin/CD62L 3 endothelial ligands - glycan-bearing CAM-1 (LN) - MadCAM-1 (gut) - CD34 (endothelial cell or BM) E-selectin/CD63E/ELAM-1: Lewis X/A family ligand P-selectin/CD62P: secretory granule of plt, Weibel-Palade body of ec
Integrins Heterodimeric (18α and 8β) cell surface proteins, about consisting of 30 homologous proteins in vertebrates Cell-ECM interaction and adhesion (fibronectin, laminin)-rgd (Arg-Gly-Asp) binding Cytoplasmic domain interacting to cytoskeleton Cell-cell interaction-complement components or surface proteins β1 /CD49a-h (α1-8)cd29 (common β 1 ): VLA (very late activation) VLA-4 (α 4 β 1 ) only on leukocytes-adhesion to endothelium via VCAM-1 interaction β2/ CD11a-cCD18:LFA (leukocyte function associated antigen) LFA-1 (CD11aCD18/α1 β2)-adhesion of lymphocytes to APC MΦ Mac-1 (CD11bCD18/CR3) extravasation, fibrinogen, complement receptor on MΦ opsonization CD11cCD18 (CR4)-extravasation
Adhesion and Transmigration (2) Mechanisms to induce leukocyte adhesion 1. Redistribution of adhesion molecules to the cell surface; P-selectin by histamine, thrombin, plt-activating factor (PAF) 2. Induction of adhesion molecules on endothelium by cytokine (IL-1/TNF) - E-selectin expression w/i 1-2 h - carbohydrate ligand on neutrophil 3. Increased avidity of Integrin binding : LFA-1/ ICAM-1 VLA4 / VCAM-1 high affinity
Chemotaxis After extravasation, leukocytes emigrate in tissue toward the site of injury. Locomotion oriented along a chemical gradient. - exogenous agents(mc); bacterial products peptide and lipid - endogenous chemoattractants 1. Components of the complement system, C5a 2. Products of the lipoxygenase pathway, mainly leukotriene B4 (LTB4) 3. Cytokines: chemokine family (IL-8) - Attaching to G-protein receptor on the surface of leukocytes - 2 nd messanger activation - Rho/Rac/cdc42 GTPase activation - Actin polymerizaton in the leading edge (filopodium)
filopodium Leukocyte Activation Responses induced on Leukocyte activation 1. Production of arachidonic acid metabolites 2. Degranulation and secretion of lysosomal enzymes and activation of the oxidative burst 3. Secretion of cytokines 4. Modulation of leukocyte adhesion molecule
Cytokines and Chemokines Cytokine: produced by Ta, MΦ, endothelium.. and modulating the function of other cell type Major cytokine to mediate inflamm: TNF, IL-1 Produced by mainly amφ Systemic acute phase response Chemokine: chemoattractant for specific types of leukocytes 40 chemokines and 20 receptors 1. C-X-C chemokine (α)-il-8, acting on neutrophil 2. C-C chemokine ( β) MCP-1, RANTES, eotaxin: attract eosinophil, basophil, monocyte and lymphocyte except neutrophil 3. C chemokine (γ) lymphotactin: lymphocyte 4. CX 3 C chemokine- fractalkine- monocyte, T-lymphocyte
Nature of leukocytes infiltration Neutrophil (6-24 h) Short-lived Apoptosis after 24-48 h (exception; pseudomonasneutrophil recruited for several days, hypersensitivityeosinophil) 1. More numerous in number 1. More numerous in number 2. Respond more rapidly to chemokines 3. Attach more firmly to the adhesion molecule on endothelial cell, such as P-selectin and E-selectin Monocyte (24-48 h) Replaced by monocytes and cumulate during the chronic inflammation (exception; viral infection-initially monocytes) Longer survive and proliferate in the tissue
Mechanism of leukocytes activation
Mechanism of leukocytes activation -Surface receptor in leukocyte activation 1. Toll-like receptors 2. Seven-transmembrane G-protein-coupled receptors 3. Phagocytes express receptors for cytokines ; IFN-γ (NK cell) major macrophage activating cytokine 4. Receptors for opsonins ( Mannose receptors) opsonization : process of coating a microbe to target it for phagocytosis opsonin ; the substance of opsonization - Antibodies : IgG - Complement proteins : C3b - Lectin : MBL ( mannose binding lectin ), fibronectin, fibrinogen, C-reactive protein
Phagocytosis 3 distinct but interrelated steps of phagocytosis 1. Recognition and attachment of the particle to be ingested by the leukocytes : require opsonization 2. Engulfment, with subsequent formation of a phagocytic vacuole 3. Killing or degranulation of the ingested material: oxygen-dependent mechanisms (ROI) and NO (from Arginine) In 1880, Metchnikoff (Russia)-phargocytosis discovery (ingestion of rose thorn by starfish larvae)-nobel prize (1908) with immunity
Activated macrophages Classically activated macrophages are induced by microbial products and cytokines, particularly IFN-γ, and are microbicidal and involved in potentially harmful inflammation. Alternatively activated macrophages are induced by other cytokines and in response to helminths, and are important in tissue repair and the resolution of inflammation. New Edition
O2-dependent killing O2-independent killing: BPI (bacteriocidal permeability increasing protein), lysozyme, lactoferrin, MBP (eosinophil in parasite), defensin (arg-rich), elastin (neutrophil)
Defects in Leukocyte Function Genetic Defects in leukocyte adhesion (LAD) LAD type 1: deficiency of β2 integrin (CD18) abnormal neutrophil adhesion, spreading, phagocytosis, and generation of the oxidative burst. LAD type 2: absence of a sialyl-lewis X, the ligand on neutrophilrequired for binding to the selectins expressed by cytokine-activated endothelium Defects in phagocytosis Chediak-Higashi syndrome : autosomal recessive condition-membrane docking and fusion defect- neutropenia, defective degranulation, and delayed microbial killing Defect of NADPH oxidase: Chronic granulomatous disease: Acquired DM- chemotaxis, adhesion, phargocytosis, microbicidal activity defect
Chemical Mediators of Inflammation Mediators origin from plasma or cell plasma; precursor forms that must be activated by proteolytic cleavages, e.q. complement, kinin. cell; sequestered in intracellular granules (histamine) or newly synthesized (prostaglandin, cytokine.) Most mediators: initially binding to specific receptors on target cells. One mediator can stimulate the release of other mediators by target cells. Mediators can act on one or few target cell types, have widespread target, or may even have differing effects, depending on cell and tissue types. potentially cause harmful effects.
Vasoactive Amines (1) Histamine Sequestered in granules of mast cells, basophils, platelets - preformed histamine is present in mast cell granule - released by mast cell degranulation in response to a variety of stimuli physical injury ( trauma, cold, heat) immune reactions anaphylatoxins (C3a, C5a) histamine-releasing proteins from leukocytes neutropeptidases (e.g., substance P) cytokines (IL-1, IL-8) - principal mediator of the immediate phase of increased vascular permeability, causing vascular gap Sir Thomas Lewis-histamine discovery
Vasoactive Amines (2) Serotonin Serotonin (5-hydroxytryptamine) a second preformed vasoactive mediator actions : similar to those of histamine in platelets and enterochromaffin cells but, not in human mast cell Serotonin inducer: PAF from mast cells platelet aggregate after contact with collagen, thrombin, ADP, and antigen-antibody complexes
Plasma Proteins Complement system Kinin system Clotting system
Complement System (1) permeability, chemotaxis, and opsonization The most critical step in the elaboration of the biologic functions is the activation of the C3 Classic pathway: triggered by fixation of C1 to antibody (IgG or IgM) combined with antigen Alternative pathway: triggered by microbial surfaces (e.g., endotoxin), aggregated Ig s, complex polysaccharides, cobra venom Lectin pathway: plasma mannose-binding lectin binds to the carbohydrate of microbes
Early step Late step
Complement System (2) 20 component proteins including cleavage forms C3 and C5 : most important inflammatory mediator Biologic function of complement system : 1. Cell lysis by MAC (membrane attack complex): C5b + C6-9 (=C5-9) 2. Biologic effect of proteolytic fragments vascular phenomena: Anaphylatoxin [C3a, C5a, > C4a] increased vascular permeability, vasodilation from histamine leukocyte adhesion, chemotaxis, and activation: C5a phagocytosis: C3b- as opsonin then, C5 convertase formation Regulatory mechanisms for preventing normal cell damage regulation of C3 and C5 convertase; DAF, factor I (C3b cleavage) binding of active C components by specific proteins in the plasma C1 inhibitor (C1INH)-C1-Ig complex CD59 (membrane inhibitor of reactive lysis)-mac inhibition
Kinin System Factor XII (Hageman factor) XIIa (activated HF) Prekallikrein kallikreins : 1. Kinin system 2. Clotting system-thrombin, fibrinopeptide, factor X 3. Fibrinolytic system plasmin 4. Complement system 1. potent Hageman activator 2. chemotactic activity 3. C5 convertase kininogen Bradykinin (vasoactive peptides) increases vascular permeability contraction of smooth muscle dilation of blood vessels pain when injected into the skin similar to histamine quickly inactivated by kininase residual kinin inactivated by angiotensin- converting enz. in lung
P-selectin mobilization Chemokine production Cox-2 induction Prostaglandin production PAF, NO production Endothelial cell shape change (PAR-1 on plt, e.c)
Sequential Events in Acute Inflammation 1) Vasodilation 2) Vascular leakage 3) Extravasation 4) Chemotaxis 5) Phargocytosis 6) Tissue Injury
Outcome of acute inflammation * Lymphatics * phargocytes
MORPHOLOGIC PATTERNS OF ACUTE INFLAMMATION Serous inflammation Fibrinous inflammation Suppurative or purulent inflammation Ulcer
SEROUS INFLAMMATION Marked by outpouring of a thin fluid Derived from either the plasma or secretions of mesothelial cells lining the body cavities (effusion)
FIBRINOUS INFLAMMATION Fibrinogen pass across vascular barrier, fibrin formed and deposted in extracellular space large vascular leak or procoagulant stimuli (Ca) lining of body cavity-meninges, pericardium, pleura When not removed, ingrowth of fibroblasts and blood vs scarring
Fibrinous pericarditis
SUPPURATIVE OR PURULENT INFLAMMATION Production of large amounts of pus or purulent exudate-pyogenic bacteria Abscess: localized collection of purulent inflammatory tissues-central necrosis with surrounding preserved neutrophils and outer vascular dilation and fibroblastic proliferation Caused by pyogenic (pus-producing) bacteria Abscess = localized collections of pus
ULCERS Local defect of the surface of an organ or tissue that is produced by the sloughing of inflammatory necrotic tissue Acute and chronic inflammation coexist Most common peptic ulcer, others in the mucosa of the mouth, GIT, or GUT and skin (sore in lower limb)
ESSENTIAL MACROSCOPIC APPEARANCES OF ACUTE INFLAMMATION 1. Reddness (rubor: rosea, purpureus) 2. Heat (calor: ardor, vapor) 3. Swelling (tumor: torus, panicula) Increased blood flow: histamine 4. Pain (dolor: vulnero, morsus)- prostaglandin, bradykinin 5. Loss of function (functio laesa)- O2 metabolite by Virchow Celsus 4 cardinal sign (BC 3,000)
CHRONIC INFLAMMATION Inflammation of prolonged duration active inflammation, tissue destruction, and attempt at repair are proceeding simultaneously frequently begins insidiously, as a low-grade, smoldering, often asymptomatic response
CAUSES OF CHRONIC INFLAMMATION Persistent infections by certain microbes (Tb bacilli, T. pallidum & certain viruses, fungi, and parasite) - organisms with low toxicity delayed type hypersensitivity (granulomatous inflammation in some) Prolonged exposure to potentially toxic agents, either exogenous or endogenous - silica (silicosis), toxic plasma lipid (atherosclerosis) Autoimmunity - autoantigens evoke a self perpetuating immune reaction that results in chronic tissue damage and inflammation - rheumatoid arthritis and lupus erythematosus
MONONUCLEAR CELL INFILTRATION Macrophages may be activated by: cytokines (IFN-γ) secreted by immune activated T cells; bacterial endotoxins and other chemical mediators Activation results in cell size, levels of lysosomal enzymes, more active metabolism, and greater ability to phagocytose and kill ingested microbes Activated macrophages secrete biologically active products that result in the tissue injury and fibrosis
THE PRODUCTS AND ROLES OF ACTIVATED MACROPHAGES IN CHRONIC INFLAMMATION
MACROPHAGE-LYMPHOCYTE INTERACTIONS IN CHRONIC INFLAMMATION
GRANULOMATOUS INFLAMMATION aggregation of macrophages (epithelioid cells) surrounded by a collar of mononuclear leukocytes tuberculosis, sarcoidosis, leprosy, brucellosis, syphilis, some mycotic infections, berylliosis, and reactions of irritant lipids Langhans-type (immune) or foreign body-type giant cells