immunopathology: hypersensitivities Flashcards
What is the definition of an allergy?
an abnormal response to an antigen, hypersensitivity
What is the definition of atopy?
hereditable susceptability to allergic reactivity
What is the definition of anaphylaxis?
systemic allergic reaction that produces shock
What is the definition of an allergen?
an antigen that causes an allergic reaction
What are the two phases in hypersensitivity?
The sensitisation phase and the effector phase
What is the sensitisation phase in hypersensitivity?
initial exposure to the antigen that ‘primes’ the response
What is the effector phase in hypersensitivity?
The subsequent exposure associated with pathology
How does Hypersensitivity I occur?
IgE antibdodies bind to mast cells
When these mast cells then come into contact with an antigen then granules are released such as histamine
eosinophils are attracted which then causes the allergic reaction
What released from mast cells mediates the anaphylaxis?
IL-6 and TNF- alpha
What released from mast cells is chemotactic for eosinophils?
IL-5
What are some of the clinical manifestations of type 1 hypersensitivity?
Usually involves the epithelial surface
Chronic dermatitis
hyperpigmentation, lichenification
What cells are consistent with late phase type I hypersensitivity?
Eosinophils and their constituent tissues
How may you test for type I hypersensitivity?
- Skin Testing
- Testing for igE antibodies
What are some of the localised reactions for type I hypersensitivity?
- Urticaria
- Flea allergy dermatitis
- Food allergies
- Atopy
