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302 Scientific basis of medicine > Immunity 2) Food allergy > Flashcards

Immunity 2) Food allergy Flashcards

1
Q

What are the classes of non-immunological adverse reactions to foods?

A 
Enzyme deficiency
 - lactase deficiency
 - alcohol dehydrogenase deficiency
Histamine reactions
Toxic
Food-sensitive migraine
Flushing in acne rosacea
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2
Q

What is a food intolerance?

A

All detrimental reactions to foods that are non-IgE mediated

Explains variety of symptoms in terms of food sensitivities

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3
Q

What is an early phase allergic reaction?

A

Exposure to allergens leads to rapid development of symptoms
Reaction develops within seconds or minutes of exposure due to binding of allergens to pre-formed IgE antibodies on surface of mast cells and basophils

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4
Q

What happens following IgE ligation?

A

IgE binds to specific allergen
Cross-linking of IgE antibodies by allergen
Clustering of FceR1 receptors
Intracellular portion of receptor becomes phosphorylated
Intracellular cascade leads to cellular activation
Mast cell degranulates releasing histamine, tryptase and other pre-formed mediators

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5
Q

What are the pharmacological effects of histamine?

A 
Capillaries dilate --> fluid leaking
Wheal and flare, swelling
Sneezing
Conjunctivitis
Oral allergy, vomiting, diarrhoea
Wheeze
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6
Q

What are the GI symptoms of an IgE mediated food allergy?

A

Oral allergy - itching, tingling, irritation

Nausea, vomiting, diarrhoea

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7
Q

What are the cutaneous symptoms of an IgE mediated food allergy?

A

Hives

Angioedema

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8
Q

What are the respiratory symptoms of an IgE mediated food allergy?

A

Upper airway symptoms

Lower airway symptoms

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9
Q

What are the cardiovascular symptoms of an IgE mediated food allergy?

A

Dizziness

Collapse due to hypotension

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10
Q

What are the general features of an IgE mediated food allergy?

A

Rapidly follows exposure
Generally multi-system
Recedes rapidly
Reproducible

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11
Q

What is skin testing used for?

A

Detect allergen-specific IgE in vivo

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12
Q

How is skin testing performed?

A

Allergen extracts applied as drops
Top layers of epidermis are punctured with lancet to allow allergen contact with cutaneous mast cells
If mast cells are sensitised, degranulation produces an itchy wheal and flare response within 15min
Requires positive and negative controls

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13
Q

What are the steps of ELISA?

A
  1. Plastics coated with purified allergen of interest
  2. Incubate with patient serum
  3. IgE antibodies in sera of sensitised patient bind to allergens
  4. Immobilised IgE antibodies detected with polyclonal anti-IgE detection antibody
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14
Q

What are the benefits of skin prick test?

A

Results on same day

Costs of single vs multiple tests are similar

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15
Q

What are the disadvantages of skin prick test?

A 
Smaller range of allergens available
Affected by medication
Need normal skin for testing
Multiple tests requires multiple punctures
Operator dependent
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16
Q

What are the advantages of serology?

A 
Available to all users via laboratory
>600 individual allergens available
Unaffected by medication
Unaffected by skin conditions
Multiple tests can be performed from a single sample
17
Q

What are the disadvantages of serology?

A

Turnaround is days to weeks
Multiple tests are expensive
Lap-dependent

18
Q

What are the disadvantages of food allergy testing?

A

Native allergens used for testing are natural products and contain a mix of different allergens
Sensitisation to different molecules produces different risk profiles and sometimes false positive or negative results

19
Q

What are primary allergens in food allergy testing?

A

Unique to allergen source
Sensitisation has a risk of severe reactions
Don’t produce false positives for other allergens
Positive by serology and skin test

20
Q

What are pan allergens in food allergy testing?

A

Found in multiple allergen sources
Usually milder reactions or no reactions
Skin tests are less sensitive compared to serology

21
Q

What are the components of peanuts?

A 
Storage proteins 
 - Ara h1
 - Ara h2
 - Ara h3
Ara h8
Ara h5
Ara h9
CCD
22
Q

What is birch oral allergy syndrome?

A

IgE directed against major birch pollen allergen cross reacts with homologous proteins in plant-derived foods

302 Scientific basis of medicine (28 decks)

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