allergy

Question 1

Outline early phase allergic reaction

Answer 1

the reaction, takes seconds or mins of exposure to the allergen, to develop

This is a result of the allergen binding to pre-formed IgE antibodies on the surface of mast cells and basophils

Question 2

What happens after the mast cell and IgE ligation

Answer 2

The cross-linking of IgE antibodies to the allergen causes the intracellular portion of the receptor to become phosphorylated which results in an intracellular cascade that leads to cellular activation,

mast cells degranulate which release histamine, tryptase and other pre-formed mediators

Question 3

what are the clinical features of anaphylaxis

Answer 3

systemic release of histamines causes generalised vasodilation and fluid loss from circulation to tissues

cutaneous: hives, angioedema
gut histamine release: vomiting and diarrhoea
mucosal histamine release: laryngeal oedema, bronchoconstriction
circulation: vasodilation. hypotension

Question 4

What is oral allergy syndrome

Answer 4

The most common type of food allergy,
oral itching upon exposure to raw fruit, nuts and veg.
IgE directed against pollen proteins cross-reacts with homologous proteins in plant-derived foods.

Question 5

Lis T-cell subsets and the interleukins they produce

Answer 5

Naive CD4 cells

• -> Th1: IFN-g
• ->Th2: IL-4,5,9 &13- consistently associated with allergic disease
• ->Th17: IL-17
• ->Treg: IL-10

Question 6

Why is Th2 response important in allergy

Answer 6

IL-4 is required for B cell class switching to IgE
IL-4 and Il-13 promote mucus hypersecretion
IL-5 is required for eosinophil survival
IL-9 recruits mast cells

Question 7

What are some treatments for allergy

Answer 7

Nasal decongestants e.g. act on a1 adrenoreceptors to cause vasoconstriction, only for short term use

B2 agonists- e.g. salbutamol, acts on lung B2 adrenoreceptors cause smooth muscle relaxation

Epinephrine- systemic adrenergic effects oppose vasodilation and bronchoconstriction

Question 8

What is a treatment of allergy that acts on the early phase mediators

Answer 8

H1 antihistamines block histamines and leukotriene receptor antagonist blocks leukotrienes

mast cells stabilizers also used, decrease degranulation
e.g. sodium cromoglycate, topical use only, short 1/2 life
poor efficacy

Question 9

Outline H1 antihistamines

Answer 9

Inverse agonists at H1 histamine receptor
best used before exposure to the allergen
1st gen e.g. chlorpheniramine e.g. piriton (sedative asf)
2nd gen e.g. loratidine (minimal sedation)

Question 10

Outline Leukotriene receptor antagonists

Answer 10

Only UK drug is montelukast

effective in reducing early allergic responses but inferior to H1 antihistamines.