Hypersensitivity 1 Flashcards
What are the 4 types of hypersensitivity disorders?
I- Immediate hypersensitivity
II- Direct cell killing
III- Immune complex mediated
IV- Delayed hypersensitivity
Allergic responses are Type _ disease.
I
An allergic reaction is an _ mediated response to an allergen.
IgE
Examples of some common allergies. (4)
- Allergic triad- asthma, eczema, rhinitis
- Urticaria
- Angioedema
- Food, drugs
Why is the prevalence of allergic disease on the rise?
DONT Memorise
Westernised countries- improved sanitation & vaccination, children have lower exposure to common pathogens.
More likely to develop allergic disease
What is the pathophysiology of allergic reactions? (4)
- Production of specific IgE directed against allergen
- IgE-allergen complex binds to mast cells via Fc receptors
- Degranulation of mast cells
- Release of pre-formed and newly synthesised inflammatory molecules eg histamine and leukotrienes
Allergic reactions occur within minutes to a couple of hours. T/F?
True
Clinical presentation of allergic diseases? (8)
- Asthma
- Urticaria
- Hay fever
- Angioedema
- Anaphylaxis
- Rhinits
- Conjuctivitis
- Diarrhoea vomiting
Some common allergens? (6)
- Pollen
- Dust mite
- Animal dander
- Nuts
- Drugs
- Venom
Upon activation, what do mast cells release?
- Preformed- Histaimen, tryptase, heparin
2. Synthesised on demand- leukotrienes, cytokines (IL4, TNF), prostaglandins
IgE antibodies bind to mast cells via _ receptors.
Fc
Mast cell release is primarily seen in the first exposure to the allergen. T/F?
False- Re-exposure triggers mast cell release
What is angioedema?
Self limiting localised swelling of tissue under submucosal membrane
What are the two types of oedema useful in clinical examination?
Pitting and non pitting
Pitting- indentation of an area remains after releasing applied pressure
Spontaneous mast cell degranulation is an example of an IgE mediated allergic reaction. T/F?
False- non IgE mediated
What are some examples of non IgE allergic reactions?
- Drugs
- Thyroid disease
- Physical urticaria (response to heat & pressure)
A common drug that can induce asthma in a a fifth of asthmatics is _.
Aspirin & other NSAIDS like ibuprofen
What specific investigations are useful for allergic diseases?
- Skin prick test. (gold standard)
- Quantitate specific IgE to specific allergen
- Challenge test- supervised exposure to putative allergen.
If acute anaphylactic reaction- check serum mast cell tryptase levels
What is quantitive IgE test?
Measures amount of IgE in serum directed against a specific allergen
Rise in tryptase levels occur in both anaphylactic and local reactions. T/F?
False- only anaphylaxis
What are the different management options for IgE mediated allergies?
- Targeted avoidance
- Block mast cell activation
- Prevent effects of mast cell activation
- Anti-inflammatories
- Anaphylaxis management
- Immunotherapy
Sodium cromoglycate is an exampe of?
Mast cell stabiliser- blocks its activation.
Used as a spray
What are the two drug classes that prevent the effects of mast cell activation?
- Anti-histamines
- Luekotriene receptor antagonist- blocks effects of leukotrienes produced by mast cells after activation. Eg Montelukast
Example of anti-inflammatories?
Corticosteroids
