Anaphylaxis Tutorial Flashcards
What is anaphylaxis?
Acute type I hypersensitivity reaction to an allergen
What are 3 sources of allergens?
- Foods - peanuts
- Drugs - penicillin (IV), anaesthetics
- Venom - bee/wasp stings
What type of cell causes anaphylaxis?
Mast cells
What are the symptoms of anaphylaxis?
- Wheezing
- Urticaria (hives)
- Rhinorrhea (runny nose) and sneezing
- Conjunctivitis
What is the signalling molecule involved in anaphylaxis?
Histamine
Where are mast cells in the body? (2)
- Connective tissue (under skin)
- Epithelia mucosae (respiratory and GI tract)
What is contained in mast cell granules? (2)
Inflammatory mediators
1. Histamine
2. Leukotrienes
What does histamine release stimulate in connective tissue vs around mucosae?
- Connective —> vasodilation
- Mucosae —> airway constriction and smooth muscle contraction
What are the 3 results of histamine action?
- Vasodilation
- Airway constriction
- Smooth muscle contraction
How are mast cells stimulated by allergens?
Binds to pre-bound IgE on mast cell FcεR1 receptors
How are histamines release stimulated?
- Allergen specific IgE pre-bound to FcεR1on mast cell
- Circulating allergen binds to IgE —> receptor cross linking
- Stimulates mast cell degranulation
What is are acute vs chronic allergic reactions referred to?
Wheal (acute) and flare (chronic)
What antibody is involved in anaphylaxis and why?
IgE
- Th2 cells activation
What causes the rashes and puffy skin in anaphylaxis?
Connective tissue mast cells stimulate vasodilation via histamine —> red and inflamed (urticaria)
How are allergies tested for?
Wheal-and-flare tests
