L4 Hypersensitivity

Question 1

Which type of hypersensitivity is associated with a weal and flare reaction?

Answer 1

Type 1

Question 2

What mediates a type 1 hypersensitivity response?

Answer 2

IgE antibodies

Question 3

True or false: Eosinophils are part of the early phase response in type 1 hypersensitivity

Answer 3

False. Eosinophils are part of the late phase response.

Question 4

What term is used to describe ‘a reaction produced by the normal immune system (directed against innocuous antigens) in a pre-sensitised host’?

Answer 4

Hypersensitivity

Question 5

What is the commonest type of hypersensitivity reaction?

Answer 5

Type 1 (anaphylactic)

Question 6

What is the immunopathogenesis for Hypersensitivity Type 1 reactions?

Answer 6

IgE-mediated degranulation of mast cells and basophils.

IgE is bound to the surface of mast cells. Upon meeting the offending antigen, IgE crosslinks with Fc receptors, creating a cascade of intracellular messaging to degranulate the mast cell. Releases histamine, proteases and chemotactic factors.

Question 7

What are the clinical features of Type 1 Hypersensitivity?

Answer 7

Fast onset (15-30min)
Weal and flare

Question 8

What is the late phase response of a Type 1 Hypersensitivity reaction?

Answer 8

Eosinophils
Th2 T cells

Release prostaglandin and leukotrienes

Question 9

What are the effects of histamine?

Answer 9

Tachycardia

Blood clots

Gastric acid secretion (vomiting + diarrhoea

Vasodilation (hypotension)

Bronchoconstriction (wheeze)

Angioedema

Adrenaline

Swelling + inflammation

Question 10

What medical emergency is an acute IgE-mediated systemic hypersensitivity reaction?

Answer 10

Anaphylaxis