Allergy Flashcards
What is hypersensitivity ?
Harmful overreaction of the immunne system to non self but harmless antigens
What are the coombs and gel classification of hypersensitivity?
Type1: ige mediated- immediate
Type 2 : cytotoxic (IgG or IgM mediated )
Type3 : immune complex mediated
type lV : t cell mediated (delayed type)
What is the mechanism of type 1 hypersensitivity ?
allergen binds to ige - mast cell degranulation - histamine release
What are the organ manifestations of type 1 hypersensitivity
Skin mucosa -45 %
Respiratory tract- 25%
Gastrointestinal tract -20%
Cardiovascular system -10%
Name common allergens in type 1 hypersensitivity
Small soluble proteins
proteases
What are diseases caused by type 1 hypersensitivity
Allergic rhinitis
Asthma
Anaphalaxsis
What is the mechanism of type 2 hypersensitivity ?
IgG or IgM bind to cell surface antigens - complement activation - cell lysis
Examples of type 2 hypersensistivity
Graves disease -autoantibodies against thyroid receptors
Myasthenia gravis - autoantibodies against act receptors
Hemolytic disease of the new born- maternal antibodies against fetal rbc
What is the mechanism of type 3 hypersensitivity
Immune complexes deposit in tissues - complement activation- neutrophil activation an inflammation
Examples of type 3
Serum sickness - immune complexes form after exposure to foreign products
Vasculitis - inflammation of blood vessels due to immune complex deposits
What is type 4 hypersensitivity?
Antigen presentation - t cell activation - delayed inflammation
what are examples of type 4
Contact dermatitis - triggered by haptens
Coeliac disease - immune response to gliadin in genetically predisposed individuals
what is the hygeine hypothesis in relation to allergies ?
Lack of exposure towards the th2 pathways increasing allergy risk
What are the main stategies for managing allergic disease :?
Avoidance of allergens
Medications - antihistamines , steriods , epinephrine
Immunotherapy
