Allergy and hypersensitivity

Question 1

What is a type 1 hypersensitivity reaction?

Answer 1

an immediate reaction to environmental antigens mediated via IgE

Question 2

What is an allergen?

Answer 2

antigens that trigger allergic reactions

Question 3

Describe the process of sensitisation

Answer 3

1. Body exposed to allergen, mostly skin, GI tract, lungs
2. Allergens that make it through physical barrier taken up by APC, processed by the cell, expressed on MHC class 2 receptor, where they are presented to naive T cells
3. Naive T cell polarised to Th2 phenotype, dictated by cytokines produced
4. Th2 produce Interleukin 4, 13, induces B cells
5. B cell class switch to IgE which can bind to allergy
6. Binds to high affinity receptors, particularly on mast cells on tissues on our body

Question 4

Does sensitisation show clinical manifestation?

Answer 4

No

Question 5

What determines the difference between Ig’s?

Answer 5

• All Ig’s have same basic structure
• What determines difference in class is a change in constant region

Question 6

Describe mast cell degranulation

Answer 6

1. Encounter with antigen leads to cross linkage of receptors through IgE’s that are bound
2. Leads to degranulation of mast cell
3. Stimulus to produce new cytokines

Question 7

What are the 2 types of receptors for IgE’s?

Answer 7

• High affinity receptor (FCER1)
• Low affinity receptor (FCER2)

Question 8

Where are high affinity IgE receptors commonly expressed?

Answer 8

On basophils, eosinophils, mast cells

Question 9

What effects does histamine have on the body?

Answer 9

vasodilation, increased capillary permeability (facilitates leakage of fluid), stimulates nerve endings, bronchoconstriction

Question 10

What is a systemic clinical syndrome in allergy?

Answer 10

Anaphylaxis

Question 11

What are clinical syndromes relating to the airways in allergy?

Answer 11

Asthma
Rhinitis

Question 12

What is a clinical syndrome relating to the eyes in allergy?

Answer 12

Allergic conjunctivitis

Question 13

What are clinical syndromes relating to the skin in allergy?

Answer 13

Urticaria
Angioedema
Atopic eczema

Question 14

What is the late phase response?

Answer 14

Initial response, return to normal, then without further exposure to allergen get late response

Question 15

What is the late phase response caused by?

Answer 15

• Because of the recruitment of other cells to lungs
  
  • Prolongs inflammatory response

Question 16

What 3 characteristics make certain proteins allergenic?

Answer 16

• Protease activity: ability to break down proteins
• Surface features of protein
• Glycosylation pattern of protein