Type 1 Hypersensitivity

Question 1

What is the defining factor of Type 1

Answer 1

Increased IgE

Question 2

What are the phases in type 1?

Answer 2

Sensitisation
Allergen reintroduction

Question 3

Phase 1

Answer 3

Sensitisation phase
* Allergen exposure via respiratory or epidermis
* APCs capture antigens
* Causes naive CD4 T cells to differentiate into T helper 2 cells - stimulates humoral response
* Release of cytokines causing B cell proliferation
* Causes class switch for B cells from IgM to IgE production
* IgE binds to mast cells and basophils - relocate to site of allergen introduction
* No clinical signs present

Question 4

Cells involved in Type 1

Answer 4

CD4 T cells - differentiate into T helper 2 cells
Mast cells
Basophils

Question 5

Phase 2

Answer 5

Allergen reintroduction
Primed IgE coated mast cells bind to antigen of allergen
Release of cytoplasmic granules from mast cells
All occurs within 15 minutes

Question 6

What do mast cells release?

Answer 6

Histamine
Heparin
Serotonin
Pro-inflammatory cytokines

Question 7

What does release of mast cell granules lead to?

Answer 7

Oedema
Broncho-constriction
Pruritus

Question 8

Anaphylaxis

Answer 8

Acute systemic manifestation of antigen or allergen binding to IgE on mast cells
Anaphylactic shock occurs within seconds to minutes in sensitised animals after exposure to allergen
Lung are primary target organs (liver in dogs)

Question 9

Treatment of anaphylaxis

Answer 9

Epinephrine to relax muscles
IV fluids
Corticosteroids

Question 10

Other example of Type 1 hypersensitivity

Answer 10

Atopic dermatitis