5-Hypersensitivity Reactions Year 4 Internal Medicine Notes

5-Hypersensitivity Reactions Year 4 · Internal Medicine Collection: 4TH YEAR ALL NOTES / IMED / I MED BEAUTIFUL NOTES / HEMAT -- Hypersensitivity \nReactions \nLecture 5\n\nImmunology433@gmail.com 11/22/13 1 \n\n Objectives Hypersensitivity reactions are over and excessive\nimmune responses that can be harmful to body in four\ndifferent ways. Be familiar with all four types.\n\nImmuno Hypersensitivity Reactions http://www.youtube.com/watch?v=E935RDEA5Qg\n\n FOUNDATION BLOCK 2 \n\nFOUNDATION BLOCK 3 \n\n What is Hypersensitivity? \n\nFOUNDATION BLOCK 4 \n\nFOUNDATION BLOCK 5 \n\nType I: Immediate Hypersensitivity n Most people will not react to these allergens but some individuals\n“atopic” respond by producing large amounts of IgE. n Non-allergic individuals respond to these allergens by producing\nIgG antibodies. Also termed as: Immediate hypersensitivity Anaphylactic reactions Allergic reactions (occurs with mins - hrs) Features: Antibody type: IgE Cellular components: mast cells, basophils, eosinophils. Antigens (Allergens): antigens with low molecular weight & high\nsolubility.\n\n FOUNDATION BLOCK 6 \n\nAntigens: Pollens • Nuts Dust mites • Shellfish Animal Dander • Various drugs\n\nReactions occur in 2 phases: 1. Sensitization phase\nFirst contact with allergens (antigens). 2. Challenge phase\nSubsequent contact with allergens.\n\n FOUNDATION BLOCK 7 \n\n Sensitization Challenge \n\nFOUNDATION BLOCK 8 \n\nPrimary & Secondary Mediators: Important\n\n FOUNDATION BLOCK 9 \n\nAllergy is a systemic disorder: Respiratory System:\nAllergic rhinitis\nAsthma Digestive System: Nose \nPharynx \nFood allergy Skin: Lungs \nEsophagus \nEczema\nUrticaria\nAllergic dermatitis Stomach \n\n Skin \n\n FOUNDATION BLOCK 10 \n\nInjected allergens: Bee sting venom enters the blood stream Systemic inflammation Anaphylactic shock (life - threatening) Anaphylactoid reactions: Are non - IgE mediated May result from contrast media or Local anesthetics Diagnosis of Allergy Skin Prick test 1. Skin prick test (SPT) 2. Specific IgE measurement (RAST) 3. Elimination / Provocation test (Food allergy) \nFOUNDATION BLOCK 11 \n\nType II: Hypersensitivity Reactions Features: IgG (or IgM) Antigens: bound to cell membranes (Self antigens) Exogenous antigens (microbial) Complement activation (Invariable) Clinical examples: Glomerulonephritis (anti-glomerular basement membrane) Mis-matched blood transfusion Diagnosis: Detection of antibodies and antigens by Immunofluorescence in tissue biopsy specimens e.g. kidney, skin.\n\n FOUNDATION BLOCK 12 \n\nType III: Immune complex hypersensitivity \n• When an antigen reacts with an antibody the product they form is\ncalled an immune complex which is capable of inducing an\ninflammatory response.\n• Immune complexes are deposited in tissues like kidneys (nephritis),\njoints (arthritis) or blood vessels (vasculitis).\n\n Type III Hypersensitivity\n(immune–complex mediated):\n\n Antibody Immune – Attraction of\n(IgG/ or IgM) Complement\n+ Antigen Complex inflammatory\nactivation \n(soluble) formation cells \n\n FOUNDATION BLOCK 13 \n\nType III H/S: Clinical examples Diagnosis \nGlomerulonephritis: Rheumatoid Demonstration of specific immune \narthritis, SLE complexes in the blood or tissues by: \nImmunofluorescence \n\n FOUNDATION BLOCK 14 \n\nType IV hypersensitivity reactions \n(Delayed Hypersensitivity) Features: Cell mediated immune response Antigen dependent T cell (CD4 generally and CD8 occasionally)\nactivation via MHC Class I or II Activated macrophages Delayed onset (2-4 days) Abnormal cellular response (Granuloma formation)\n\n FOUNDATION BLOCK 15 \n\n Mediators released by TDTH\ncells\n\n FOUNDATION BLOCK 16 \n\nDevelopment of DTH Response: Sensitization phase: (1-2\nweek period) Effector phase: (24-72 hours) Effector cells\n(activated macs)\nact non-specifically\n\n FOUNDATION BLOCK 17 \n\nPathophysiology of allergic contact dermatitis\n\nFOUNDATION BLOCK 18 \n\nType IV clinical examples: Allergic contact dermatitis TB granuloma (persistent antigen) Diagnosis (Type IV) Delayed skin test (Mantoux test) Patch test (Contact dermatitis) Lymphocyte transformation test Allergy Skin Patch Test:\n\n FOUNDATION BLOCK 19 \n\n Remember 1. Type I (IgE), II (IgG) and III (IgG) hypersensitivity\nreactions are mediated by antibodies. 2. Type IV hypersensitivity reaction is a cell\nmediated immune response. 3. Hypersensitivity reactions are undesirable,\nexcessive, and aberrant immune responses\nassociated with disorders such as allergy,\nautoimmunity and chronic inflammation.\n\n FOUNDATION BLOCK 20