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Path Y > Immunology - Allergy > Flashcards

Immunology - Allergy Flashcards

1
Q

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

A

Microbe: PAMP is recognised –> Th1 and Th17 response

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

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2
Q

How does Th2 activation cause mast cell degranulation?

A

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

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3
Q

Why does atopic dermatitis predispose to allergic sensitisation?

A

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

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4
Q

Which interleukin is most important in Th2 cell responses?

A

IL4

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5
Q

Why do filagrin mutations increase risk of allergic disease?

A

Increase risk of atopic dermatitis which increases allergen exposure

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6
Q

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

A

Wheal >3mm bigger than control

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7
Q

Recall 2 limitations of skin prick allergy testing

A
  1. risk of anaphylaxis (1 in 3000)
  2. poor positive predictive value
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8
Q

What can component resolved diagnostc testing be useful for?

A

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

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9
Q

What is a measurement of mast cell tryptase used for?

A

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

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10
Q

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

A

Challenge tests

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11
Q

How should an allergy challenge test be performed?

A

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

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12
Q

Describe the symptoms of the oral allergy syndrome

A

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

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13
Q

Recall some foods that may trigger the Latex Food Syndrome?

A

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

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14
Q

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

A

Positive: histamine
Negative: diluent

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15
Q

Recall the management of anaphylaxis in adults

A

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

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16
Q

allergic disorder is what type of hypersensitivity disorder

A

type 1

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17
Q

allergens trigger release of what Ig

A

IgE

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18
Q

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

A

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

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19
Q

diagnosis of allergic disease requires what

A

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

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20
Q

give 5 indications of an IgE RAST blood test

A

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

21
Q

What cells and mediators in the IgE mechanism

A

masts cells and basophils
histamine and platelet activating factor

22
Q

What cells and mediators in the IgG mechanism

A

macrophages and neutrophils
histamine and PAF

23
Q

What cells and mediators in the complement mechanism

A

mast cells and macrophages
histamine and PAF

24
Q

What cells and mediators in the pharmacological mechanism

A

mast cells
histamine and leukotriene

25
Q

4 examples of IgE allergens

A

food, insect venom, ticks, penicillin

26
Q

3 examples of IgG allergens

A

biologicals, blood and IgG transfusions

27
Q

4 examples of complement allergens

A

lipid excipients, liposomes, dialysis membranes and polyethylene glycol

28
Q

4 examples of pharmacological allergens

A

NSAIDS - aspirin
opiates
neuromuscular drugs
quinolone

29
Q

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

A

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

30
Q

how do you diagnose anaphylaxis

A

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

31
Q

treatment of anaphylaxis

A

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

32
Q

what does the emergency community anaphylaxis kit containing

A

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

33
Q

outline the supportive treatment of anaphylaxis

A

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

34
Q

alpha 1 mechanism in anaphylaxis

A

peripheral vasoconstriction

35
Q

beta 1 mechanism in anaphylaxis

A

increases heart rate, contractility and BP

36
Q

beta 2 mechanism anaphylaxis

A

relaxes bronchial smooth muscle and reduces release of inflammatory mediators

37
Q

distinguish between food allergy and intolerance

A 
allergy = immune response 
intolerance = non-immune
38
Q

state a non IgE mediated disease

A

coeliac

39
Q
A
40
Q

state a cell mediated disease

A

contact dermatitis

41
Q

what type of reaction is anaphylaxis

A

IgE mediated

42
Q

what 3 tests are sensitisation tests be used first line

A

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)

43
Q

what 3 tests are diagnostic

A

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

44
Q

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

A

OAS

45
Q

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

A

delayed food induced anaphylaxis to beef, pork, lamb

46
Q

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

A

food associated exercise induced anaphylaxis

47
Q

in skin prick what are the positive and negative controls

A

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.

48
Q

whats latex food synfrome and oas

A

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.

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