10 Allergy

Question 1

What is the body’s response to parasitic disease?

Answer 1

Increased IgE levels.
Tissue inflammation with eosinophils, basophils and mastocytosis.
Presence of CD4+ T cells secreting IL4, IL5, IL13.

Question 2

What is the hygiene hypothesis?

Proposed mechanism?

Answer 2

Stimulation by microbes is protective against autoimmunity.

Th1 Th2 deviation - if Th1 (infection) has nothing to work on Th2 increases.

Question 3

Which genes have influences on the ‘allergic’ immune response? (5).

Answer 3

Cytokine gene cluster IL3,5,9,13
IL12R, IL4R.
FcεRI.
IFNγ.
TNF.

Question 4

Beginning with a Th2 cell, how is mast cell degranulation achieved>

Answer 4

Th2 cell uses IL4 and IL13 to stimulate B cell into proliferating and producing IgE. IgE binds to sensitised mast cells which degranulate.

Question 5

Mast cells have initial and late phase responses, which chemicals characterise both?

Answer 5

Initial: histamine, proteases, chemotactic factors (ECF, NCF).
Late: Arachidonic acid derivatives - leukotrienes, prostaglandin.

Question 6

What is the atopic triad diseases?

Answer 6

Asthma, rhinitis, eczema.

Question 7

What is rhinitis? What are the common allergens?

Answer 7

Allergic response in upper respiratory tract and eyes.

Animal dander, pollen, house dust mite.

Question 8

Rx for rhinitis?

Answer 8

Antihistamines and nasal steroids.

Question 9

What is allergic asthma?

Answer 9

IgE mediated allergy. Late phase response causes away damage. Damaged tissue becomes hyper-reactive to other stimuli e.g. fumes.

Question 10

What is atopic dermatitis? Rx?

Answer 10

Allergy resulting in blistering, itching, cracking of skin. Major trigger is dust mite.
Rx: topical steroids and moisturisers.

Question 11

What is the trinity of interplaying factors in atopic dermatitis?

Answer 11

Barrier disruption.
Parities/itch.
Development of AD (Th2).

Question 12

Which tests are available to diagnose anaphylactic reactions? (6).

Answer 12

Specific IgE (>0.35KuA/L)
Skin prick test (>3mm wheal).
Intra-dermal test.
Oral challenge (gold standard).
Basophil activation test (research, not clinical).
Component resolved diagnostics.

Question 13

How is a skin prick test carried out?

Which drugs common affect this test?

Answer 13

-ve control (saline), +ve control (histamine), exposure.

Anti-histamines and tri-cyclic antidepressants.

Question 14

What are the symptomatic therapies for anaphylactic reactions? (3).

Answer 14

Anti-histamines.
Steroids.
Adrenaline.

Question 15

What are the indications for immunotherapy for anaphylactic allergies? (3).

Answer 15

Life-threatening reaction to wasp/bee sting.
Severe hay fever.
Animal dander allergy.

Question 16

What is the mechanism behind immunotherapy?

Answer 16

Purposeful exposure to allergen at increasing doses. Try to divert Th2 to Th1 response. Induce Treg cells and stimulate B cells to increased antibody competition.

Question 17

What are the clinical manifestations of a food allergy? (5).

Answer 17

D+V.
Bronchospasm.
Urticaria.
Angiodema.
Anaphylaxis.