Experimental induced anaphylactic response in lab. animal Part 1 Aim of practical •Introduction to hypersensitive reactions •Immediate hypersensitivity • • •Counting of blood elements - eosinophils, WBC and platelets • Hypersensitivity •Positive or negative? • •The term hypersensitivity is used to describe immune responses that are damaging rather than helpful to the host. • •Why? Hypersensitivity •Gell and Coombs clasification –Type I - immediate hypersensitivity –Type II - is caused by specific antibody binding to cells or tissue antigens –Type III - is mediated by immune complexes –Type IV - is the only class of hypersensitive reactions to be triggered by antigen-specific T cells Immediate hypersensitivity: Type I IgE antibody Mast cells and their mediators (vasoactive amines, lipid mediators, cytokines) Antibody mediated: Type II IgM, IgG antibodies against cell surface or extracellular matrix antigens Opsonization and phagocytosis of cells Complement-and Fc receptor-mediated recruitment and activation of leukocytes (neutrophils, macrophages) Abnormalities in cellular functions, e.g., hormone receptor signaling Immune complex mediated: Type III Immune complexes of circulating antigens and IgM or IgG antibodies Complement-and Fc receptor-mediated recruitment and activation of leukocytes T cell mediated: Type IV 1. CD4+ T cells (delayed-type hypersensitivity) 2. CD8+ CTLs (T cell-mediated cytolysis) 1. Macrophage activation, cytokine-mediated inflammation 2. Direct target cell killing, cytokine-mediated inflammation Type of hypersensitivity Pathologic immune mechanisms Mechanisms of tissue injury and disease In 1906 C.Pirquet and B.Schick observed unwanted reactivity in chlildren after repeated application of diphteric serum – they called the reaction serum illness – term „allergy“ 􀃊 In 1911 Ch.Richet and P.Portier studied influence of extract of sea animals (jelly-fish) in dogs. Rapid shock reaction which followed they termed as anaphylactic – unwanted (in contrast with prophylaxis) 1920 A.F.Coca atopy vs. genetically predisposition History Allergy vs. anaphylaxis vs. atopy • Allergy - Allergy is a disorder of the immune system that is often called atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. • Anaphylaxis Anaphylaxis is an acute systemic (multi-system) and severe Type I Hypersensitivity allergic reaction in humans and other mammals. The term comes from the Greek words ανα ana (against) and φύλαξις phylaxis (protection). • Atopy Atopy (Greek ατοπία - placelessness) or atopic syndrome is an allergic hypersensitivity affecting parts of the body not in direct contact with the allergen. It may involve eczema (atopic dermatitis), allergic conjunctivitis, allergic rhinitis and asthma. There appears to be a strong hereditary component Immediate hypersensitivity •The typical sequence of events in immediate hypersensitivity consists of: • exposure to an antigen • activation of TH2 cells specific for the antigen, • production of IgE antibody • binding of the antibody to Fce receptors of mast cells • triggering of the mast cells by re-exposure to the antigen, resulting in the release of mediators from the mast cells and the subsequent pathologic reaction showimage Mast cell mediators. Upon activation, mast cells release various classes of mediators that are responsible for the immediate and late-phase reactions. ECF, eosinophil chemotactic factor; NCF, neutrophil chemotactic factor (neither of these has been biochemically defined); PAF, platelet-activating factor. IMG_011 IMG_012 Mast cell, intact (left) and degranulated (right) Immediate hypersensitivity •The clinical and pathologic manifestations of immediate hypersensitivity consist of the: • • vascular and smooth muscle reaction that develops rapidly after repeated exposure to the allergen (the immediate reaction) • • and a delayed late-phase reaction consisting mainly of inflammation •Immediate hypersensitivity reactions are manifested in different ways, including: • • skin and mucosal allergies, • food allergies • asthma • systemic anaphylaxis The immediate and late-phase reactions The immediate vascular and smooth muscle reaction to allergen develops within minutes after challenge Morphology of basophils and eosinophils Eosinofily C:\Dokumenty\Histologie\VYUKA\krev\005.jpg Basofily C:\Dokumenty\Histologie\VYUKA\krev\008.jpg Mast cell • •Respiratory and gastrointestinal system, derm •Population of mast cells differ by type and amount od mediators •Mast cells produce various cytokines: IL-1, IL-3, IL-4, IL-5, IL-6, GM-CSF, TGF-β, TNF-α • Obrázek6 Mast cell activation •Mast cells are activated by cross-linking of FcεRI molecules, which occurs by binding of multivalent antigens to the attached IgE molecules • •Activation of mast cells results in three types of biologic response: –secretion of the preformed contents of their granules by a regulated process of exocytosis, –synthesis and secretion of lipid mediators, –and synthesis and secretion of cytokines Activation of mast cells Mast cell degranulation mast cell degranulation Mediators derived from Mast Cells •The effector functions of mast cells are mediated by soluble molecules released from the cells on activation • •These mediators may be divided into preformed mediators, which include biogenic amines and granule macromolecules, and newly synthesized mediators, which include lipid-derived mediators and cytokines •Biogenic amines –histamine •Granule proteins and proteoglycans (Enzymes) –Serine proteases •Lipid mediators –Prostaglandins, leukotrienes •Cytokines –TNF, IL Mediators derived from Mast Cells Biological effect of mediators Biological effect of histamine •H1 receptor • - bronchoconstriction • - vascular leak • - vasodilatation •H2 receptor • - secretion of HCl • - release of histamine • - regulation on immune response •H3 receptor obr12 Types of histamine receptors •H1- receptors –Constriction of smooth muscle –Increased vascular leak –Irritation of sensitive nerves –Hypersecretion in salivary gland •H2-receptors –Stimulation of HCl secretion –Positive chronotropic and ionotropic effect –Anaphylaxis – •H3-receptors (nerve cells). –Regulatory function – after activation – decrease of histamine and other mediators production in CNS •H4-receptory - eosinophils, bone marrow, lung –Regulation of immune system Hypersensitive reaction – type I •Systemic (anaphylactic reaction) • - generalized, endangering life, shock • - anaphylactoid reaction •Localized reaction §Asthma bronchiale §Nasal allergy §Atopic dermatitis §Food allergy • Úloha žírných buněk u anafylaxe Anafylaxe antigen IgE Anafylaktoidní reakce neimunologická komplement C5a C3a Mastocyt granula Histamin Kallikrein ECF-A NCF-A syntéza proteinů cytokiny TNFα, TGFβ, IL5, IL6 novotvorba PAF, prostaglandiny, leukotrieny Clinical picture and manifestation •Mucous membrane, derm –Erythema, exanthema, pruritus, edema •Respiratory system – Acute rhinitis, nasal obstruction, sneezing, irritation to cough, breething problems •GIT – vomitus, colic, diarrhoea Symptoms depend on: •Sesibilization level of patient •Place of allergen entry •Allergen type Symptoms Cardiovascular system: Palpitation, tachycardia, hypotension, arrhytmia Urogenital system: Picture of renal colic General symptoms: Cognition disorders, spsms !!Reason of death!! Respiratory failure, cardiovascular failure Treatment Adrenaline i.v. Corticosteroids i.v. - Inhibition of leucotrien synthesis -Inhibition of inflammatory cells infilration in place of allergy reaction - Inhibition in cytokine production Antihistaminics Antihistaminics Inhibition of H1 and H2 receptors in terminal cells Theophylin Prolongation of increasing level of cAMP in mast cells Adrenaline Stimulation of cAMP production due to binding to b-receptors in mast cells Corticosteroids Inhibition of leucotrien and cytokine synthesis Practical part