Immunology - Allergy

Question 1

What is the difference in CD4 T cell response between microbial recognition and allergen recognition?

Answer 1

Microbe: PAMP is recognised –> Th1 and Th17 response

Allergen/Helminth/Worms: functional change is recognised (eg tissue damage) –> Th2 response

Question 2

How does Th2 activation cause mast cell degranulation?

Answer 2

Th2 secretes IL4
IL4 activates B cells to produce IgE
IgE causes mast cells to degranulate and secrete:
- prostaglandins
- leukotrienes
- histamines

Question 3

Why does atopic dermatitis predispose to allergic sensitisation?

Answer 3

Skin exposure more likely to lead to IgE response than oral exposure (oral promotes immune tolerance)

Question 4

Which interleukin is most important in Th2 cell responses?

Answer 4

IL4

Question 5

Why do filagrin mutations increase risk of allergic disease?

Answer 5

Increase risk of atopic dermatitis which increases allergen exposure

Question 6

What represents a positive result in a skin-prick allergy test?

Answer 6

Wheal >3mm bigger than control

Question 7

Recall 2 limitations of skin prick allergy testing

Answer 7

1. risk of anaphylaxis (1 in 3000)
2. poor positive predictive value

Question 8

What can component resolved diagnostc testing be useful for?

Answer 8

For nuts, detection of storage protein is indicative of a stronger reaction

For wheat, detection of omega-5-gliadin is indicative of a stronger reaction

Question 9

What is a measurement of mast cell tryptase used for?

Answer 9

Biomarker for anaphylaxis that peaks 1-2 hours following a reaction
Useful if diagnosis of anaphylaxis is not clear

Question 10

What is the gold standard method of allergy testing/diagnosis?

Answer 10

Challenge tests

Question 11

How should an allergy challenge test be performed?

Answer 11

Increase volume of allergen and measure response - it is the gold standard for food allergy diagnosis (done as a double blind)

Question 12

Describe the symptoms of the oral allergy syndrome

Answer 12

Symptoms of allergy limited to mouth
Common allergens = birch pollen + rosacea fruit + ragweed + melons + mugwort + celery (due to cross reactivity)

Question 13

Recall some foods that may trigger the Latex Food Syndrome?

Answer 13

Chestnut
Avocado
Banana
Potato
Tomato
Papaya
Kiwi
Aubergine
Mango
Wheat
Melon
Latex

Question 14

What are the positive and negative controls used in skin prick testing?

Answer 14

Positive: histamine
Negative: diluent

Question 15

Recall the management of anaphylaxis in adults

Answer 15

Elevate legs
100% oxygen
IM adrenaline 500 mcg
Inhaled bronchodilators
Hydrocortisone 200mg IV
Chlorphenamine 20mg IV
IV fluids
Seek help

Question 16

allergic disorder is what type of hypersensitivity disorder

Answer 16

type 1

Question 17

allergens trigger release of what Ig

Answer 17

IgE

Question 18

what is the sensor in the TH2 immune memory response? what is released subsequently

Answer 18

mast cell = sensor
allergen causes cross linking of IgE
releasing histamine, prostaglandin and leukotriene

Question 19

diagnosis of allergic disease requires what

Answer 19

history - occurs minutes to 3 hours after exposure, usually 2 organ systems involved
examination
allergic specific IgE (sensitisation) test

Question 20

give 5 indications of an IgE RAST blood test

Answer 20

if patient can’t stop antihistamunes
patient has dermatogrophism
extensive eczema
history of anaphylaxis
borderline skin prick result

Question 21

What cells and mediators in the IgE mechanism

Answer 21

masts cells and basophils
histamine and platelet activating factor

Question 22

What cells and mediators in the IgG mechanism

Answer 22

macrophages and neutrophils
histamine and PAF

Question 23

What cells and mediators in the complement mechanism

Answer 23

mast cells and macrophages
histamine and PAF

Question 24

What cells and mediators in the pharmacological mechanism

Answer 24

mast cells
histamine and leukotriene

Question 25

4 examples of IgE allergens

Answer 25

food, insect venom, ticks, penicillin

Question 26

3 examples of IgG allergens

Answer 26

biologicals, blood and IgG transfusions

Question 27

4 examples of complement allergens

Answer 27

lipid excipients, liposomes, dialysis membranes and polyethylene glycol

Question 28

4 examples of pharmacological allergens

Answer 28

NSAIDS - aspirin opiates neuromuscular drugs quinolone

Question 29

give 2 conditions that mimic anaphylaxis but will not respond to IM adrenaline

Answer 29

C1 inhibitor deficiency - throat swelling chronic urticaria and angiodema- ace inhibitors

Question 30

how do you diagnose anaphylaxis

Answer 30

measurement of serum tryptase (specific marker for mast cell degranulation ) taken at 1, 3 and 24 hours post episode usually peaks around 3 hours and declines persistent rise 24 hours after is suggestive of systemic mast cell disease suc as mastocytosis not anaphylaxis

Question 31

treatment of anaphylaxis

Answer 31

IM dose of (0.5ml of adrenaline 1/1000).

Question 32

what does the emergency community anaphylaxis kit containing

Answer 32

epic pen with 300 micrograms or half if child prednisolone 20mg OD cetirizine 10mg 0D (antihistamine)

Question 33

outline the supportive treatment of anaphylaxis

Answer 33

100% oxygen fluid replacement IV hydrocortisone 100mg IV chloramphenamine (for itch) inhaled bronchodilators

Question 34

alpha 1 mechanism in anaphylaxis

Answer 34

peripheral vasoconstriction

Question 35

beta 1 mechanism in anaphylaxis

Answer 35

increases heart rate, contractility and BP

Question 36

beta 2 mechanism anaphylaxis

Answer 36

relaxes bronchial smooth muscle and reduces release of inflammatory mediators

Question 37

distinguish between food allergy and intolerance

Answer 37

``` allergy = immune response intolerance = non-immune ```

Question 38

state a non IgE mediated disease

Answer 38

coeliac

Question 40

state a cell mediated disease

Answer 40

contact dermatitis

Question 41

what type of reaction is anaphylaxis

Answer 41

IgE mediated

Question 42

what 3 tests are sensitisation tests be used first line

Answer 42

gold - skin prick (intardermal) - exclude allergy high NPV RAST IgE blood test - exclude allergy high NPV CRD - detects IgE to single protein components (e.g peanut and hazelnut)

Question 43

what 3 tests are diagnostic

Answer 43

serum mast cell tyrptase - diagnose anaphylaxis basophil activation - food and drug allergy gold- allergen challenge - food and drug allergy

Question 44

in what IgE mediated food allergy syndrome do cooked allergens cause no symptoms

Answer 44

OAS

Question 45

IgE against alpga-gal (a1, 3-galactose) occur in what food allergy syndrome

Answer 45

delayed food induced anaphylaxis to beef, pork, lamb

Question 46

exercise 4-6 hours after ingestion of allergen causes anaphylaxis in what syndrome

Answer 46

food associated exercise induced anaphylaxis

Question 47

in skin prick what are the positive and negative controls

Answer 47

Histamine is injected as a positive control, saline as a negative. Antihistamines must be stopped 48 hours prior to the test to allow for an accurate result.

Question 48

whats latex food synfrome and oas

Answer 48

Latex food syndrome is an IgE mediated type 1 hypersensitivity reaction to fruits and seeds, that is caused by cross-reactivity to latex antigens. To have latex food syndrome, someone must also be allergic to latex. Common fruits that may cause symptoms include: Banana, pineapple or avocado. It is diagnosed via skin prick testing, demonstrating an allergy to latex and other foods. Oral allergy syndrome refers to a collection of mild symptoms that occur when a patient eats typically stony fruit or some vegetables.