Hypersensitvity and the skin Flashcards
1
Q
What is an Allergy?
A
A reaction of the immune system to a harmless substance in the environment.
2
Q
What is the timescale of a Type 1 Allergy?
A
minutes to 2 hours
3
Q
Describe the pathophysiological progression of Type 1 allergic response.
A
- Allergen uptake by dendritic cells
- activation of allergen-sepcific T cells to Th2 cells
- B cell activation
- Allergen-specific IgE is produced in excess. It coats Mast cells
- Binding of allergen to IgE on mast cell surface triggers release of:
- hstamines
- leukotrienes
- cytokines
- prostaglandins
4
Q
What is the clinical presentation of Type 1 hypersenistivity (allergy)?
A
- Utricaria (hives)
- Angioedema
- Wheezing/asthma
- Anaphylaxis
5
Q
What investigations are used for Type I allergies?
A
- history
- specific IgE test
- skin prick test
- challenge test
- serum mast cell tryptase level (durig anaphylaxis)
6
Q
Type I allergy management?
A
- anti-histamines
- anti-inflammatories (corticosteroids)
- adrenaline autoinjector (for anaphylaxis)
7
Q
Timescale of Type IV Allergy?
A
24-48 hours onset
8
Q
Type IV Allergy/hypersensiticity is mediated by ____
A
T cells
9
Q
What is the pathophysiology of Type IV allergy?
A
- Dendritic cells present allergen to T cells, activating them. These migrate to tissues (also skin)
- Repeat exposure to allergen activates CD8+ cytotoxic T cells, which cause apoptosis and release cytokines/chemokines.
10
Q
What are the causes of Irritant contact dermatitis?
A
Contact with agents that irritate the skin directly
-NOT allergic
11
Q
How are Type IV allergies managed?
A
Emollients
Topical steroids
UV phototherapy
Immunosuppressants
