7015972
Description
Flashcards by Rachael Jones, updated more than 1 year ago
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Created by Rachael Jones
about 8 years ago
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| Question | Answer |
| What is hypersensitvity? | An individual who has been sensitised to a particular antigen by repeated exposure over time is susceptible to developing an excessive immune response (hypersensitivity reaction) on subsequent exposure to the antigen |
| What causes hypersensitivity? | Antigens (allergens) involved are generally ubiquitous environmental substances to which only genetically susceptible individuals react inappropriately |
| Is there only one cause for allergy? | No - multifactorial |
| What does the hypersensitivity response result in? | Cellular and tissue changes and clinical signs of allergic disease |
| Is the same hypersensitivity mechanism used for useful purpose and for foreign antigen? | Yes |
| What is another name for 'hypersensitivity mechanisms'? | Immunopathological mechanisms |
| What are the 4 classifications of hypersensitivity? | 1. Type I - immediate 2. Type II (antibody dependent: - cytotoxic type, - anti-receptor type) 3. Type III- immune complex 4. Type IV - cell mediated/ delayed type hypersensitivity (DTH) |
| What are the 2 stages of a hypersensitivity reaction? | 1. Sensitisation 2. Hypersensitivity |
| What is the process of sensitisation in type 1 hypersensitivity? | 1. Allergen is recognised by dendritic cell 2. Allergen grabbed and internalised by DC which then migrates to lymph tissue 3. Th2 produce specific cytokines 4. Cytokines act on allergen specific B cells 5. B cell produce allergen specific IgE |
| What is the hypersensitivity stage of type I? | 1. The allergen is recognised by the IgE which coats mast cells 2. Cross-linking of allergen by IgE causes degranulation of mast cell 3. Cuasing bronchoconstriction, vasodilation, pruritus within 5-60 mins (usually 15) |
| What is related to mast cell degranulation between 4-24 hours after? | Late phase recruitment of eosinophils and macrophages - inflammatory cells |
| What does the allergen cross link? | IgE bound to FCER |
| What leads to the degranulation of the mast cells? | Intracellular signalling pathway |
| What may also coat mast cells (reagenic antibody)? | IgG (of a particular subclass) |
| Give 3 other substances that can degranulate mast cells. | 1. C3a 2. C5a 3. Neuropeptide |
| Give 3 localised type 1 hypersensitivity disease. | 1. Cutaneous (eg flea allergy) 2. Respiratory (eg asthma) 3. Intestinal (eg food allergy) |
| Give 3 systemic type 1 hypersensitivity disease. | 1. Anaphylaxis (eg bee sting, penicillin reaction) 2. Severe and life threatening 3. Bronchoconstriction, laryngeal oedema, vasodilation |
| How is type 1 hypersensitivity regulated? | The lack of Tregulatory activity causes there to be an increase in Th2 |
| What does an increase in Th2 cause? | - IgE production - Eosinophil attraction (IL-5, eotaxin) - Mast cell attraction (IL-4) |
| What 2 cell types will be found in a histological section of a canine asthma-like disease? | 1. Bronchial mast cells 2. Bronchial CD4+ T cells |
| Give 7 factors that cause allergy. | 1. Age 2. Parasitism? 3. Microbial infection 4. Stress 5. Immune dysregulation 6. Allergen exposure 7. Genetic |
| What are the 2 things that have influenced the cause of the hygiene hypothesis? | The way we live How we bring up kids |
| Give 7 factors that influence the hygiene hypothesis. | 1. Isolation 2. Cleanliness 3. Processes foods 4. Vaccination 5. Antibiotic usage 6. Allergy 7. Autoimmunity |
| Is the allergic incidence increasing or decreasing? | Increasing |
| What does repeated infection cause with relation to the hygiene hypothesis? | - Induces Tregulatory cells - Causing 'bystander suppression' and non microbe-specific - No Th1 or Th2 induced - Controls autoimmunity/ allergy |
| What does lack of microbial exposure cause with relation to the hygiene hypothesis? | - Reduces expansion - Increases autoimmunity and allergy - Th1 and Th2 produced |
| What are the 3 ways an antibody can kill a target cell? | 1. Opsonisation 2. Complement mediated lysis 3. ADCC through the binding of FcR of a natural killer cell to target cell |
| Give 3 examples of when there is type II hypersensitivity. | 1. Blood transfusion reactions 2. Antibody-mediated autoimmune diseases 3. Graft rejection |
| Why might a type II hypersensitivity reaction occur in dogs with transfusion reactions? | DEA1- dog given DEA1+ blood on two occasions (induced alloantibody) - make antibody on the first occasion and then will hypersensitivity on second time due to antibody attacking 'foreign' antigen |
| Why might a type II hypersensitivity reaction occur in cats with transfusion reactions? | Transfuse type B cat with type A or AB blood (naturally occurring alloantibody against type A) |
| Give 2 outcomes of blood transfusion reactions. | 1. Acute angioedema 2. Chronic haemolytic |
| Give an autoimmune disease which is a type II hypersensitivity reaction to the antibody. | Autoimmune haemolytic anaemia (AIHA) |
| What happens in AIHA? | Attack own red blood cells due to marcophages with FcR and C3bR |
| What is the anti-receptor antibodies (subtype of type II hypersensitivity) also referred to as? | Type V hypersensitivity |
| Give an example of a receptor stimulating antibody disease in type II hypersensitivity. | Grave's disease |
| How does Grave's disease work? | Anti-TSHR (thyroid stimulating hormone receptor) antibody binds to TSHR to cause prolonged stimulation of the pituitary and therefore excess hormone is produced |
| Give a disease that involves receptor blocking antibodies in type II hypersensitivity. | Myasthenia Gravis |
| What happens in Myasthenia Gravis? | The antibody blocks the Ach receptor and therefore Ach can't bind resulting in the muscle motor end plate not working due to no stimulation (neuromuscular junction) |
| What are the clinical signs of Myasthenia Gravis? | Episodic walking and collapsing due to the AchR being blocked/destroyed |
| What are the 2 sub types of type III hypersensitivity? | 1. Antibody 2. Antigen |
| What happens in type III when there is antibody in excess? | - Sensitisation leads to IgG response - Local exposure to antigen - Local immune complex formation - Local inflammation - The 'Arthus Reaction' |
| What can the antigen entering where the antibody is in excess cause? | 1. Complement activation ( causes neutrophil degranulation, mast cell degranulation, platelet aggregation microthrombi- inflammation) 2. Macrophage activation ( IL-1, TNF - Inflammation) |
| Give 3 human arthus reactions (occupational diseases). | 1. Farmer's lung (fungal spores) 2. Pigeon Fancier's lung 3. Cheesemaker's lung |
| What happens in type III when there is antigen in excess? | - Sensitisation leads to circulating antibody - Exposure to high concentration antigen - Small soluble immune complexes in antigen excess - Circulating immune complexes - Systemic disease |
| What is the effect of antibody-antigen complex sitting in the wall of a blood vessel when there is excess antigen? | - Complement activation - Neutrophil degranulation - Basophils - Platelet aggregation microthrombi - Vasodilation - Vasculitis - Inflammation |
| Why do immune complexes fall out of blood vessels? | Turbulent blood flow |
| Give 4 places where it is common to get localisation of circulating immune complexes. | 1. Renal glomerulus 2. Eye 3. Skin between epidermis and dermis 4. Synovium of joints |
| Give 6 factors that determine the immune complex deposition. | 1. Size of complex 2. Overwhelmed IC clearance mechanisms 3. Nature of antigen 4. Nature of antibody 5. High blood pressure and turbulent flow 6. Endothelial lesions |
| What is another term used to describe type IV hypersensitivity? | Delayed type hypersensitivity (DTH) |
| What is involved in type IV hypersensitivity? | Mononuclear cells and cytokines due to contacting the allergen |
| How long does it take for the DTH to occur? | 24-72 hours |
| What is stimulated in a DTH? | Sensitised memory Th1 which release IFN-gamma which recruits other cells to the tissue and producing a localised immune tissue response |
| What cells are recruited by the IFN-gamma? | Macrophae (IL-1, TNF, IL-6) Th1 CD8 NK |
| What is an example of a DTH in human medicine? | Heaves test for the BCG injection against TB - larger response means the body is more sensitised and therefore higher level exposure has been had |
| What everyday compounds can cause a DHT? | Sensitization by metal |
| How has veterinary medicine been seen to cause a DTH? | Reaction to neomycin containing topical - use of an ear infection cream as topical to an infection on the snout |
| What was the initial purpose of hypersensitivity reactions? | Defend the body from infection |
| What does a type 1 hypersensitivity reaction help to protect against? | Anti-parasitic |
| What does a type IV hypersensitivity reaction help to protect against? | Tuberculosis |
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