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ESA3 > Infection 9 - Allergies > Flashcards

Infection 9 - Allergies Flashcards

1
Q

What is a hypersensitivity reaction?

A

Immune responses that are either inappropriate or excessive, and result in harm to the host

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2
Q

In which phase of a hypersensitivity response are there no clinical manifestations?

A

Sensitization phase (1st encounter with antigen)

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3
Q

What is the most common hypersensitivity reaction ‘allergies’?

A

Type I = IgE mediated

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4
Q

Which antibody mediates allergic reactions?

A

IgE

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5
Q

List some symptoms of a Type I ‘allergic’ hypersensitivity reaction:

A
  • Urticaria
  • Eczema
  • Rhinitis
  • Asthma
  • Gastroenteritis
  • Angioedema
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6
Q

List some common allergens which trigger a Type I hypersensitivity reaction:

A
  • House dust mite
  • Animals
  • Tree/grass pollen
  • Insect venom
  • Medicines
  • Chemicals (ie latex)
  • Foods (ie milk, eggs, peanuts, seafood)
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7
Q

What must happen for a mast cell to degrade when triggering a type I hypersensitivity reaction?

A

The antigen must cross-link 2 antigen-specific IgE expressed on the mast cell

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8
Q

What happens if an antigen cross-links 2 antigen-specific IgE expressed on a mast cell?

A

Mast cell begins degradation, triggering:

  • Release of Histamine and Chemokines
  • Synthesis of Leukotrienes and Prostaglandins

= Increased vascular permeability, vasodilation, bronchoconstriction

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9
Q

What complication occurs if an allergen causes the systemic activation of Mast cells?

A

Anaphylaxis

  • hypotension
  • angioedema
  • general urticaria
  • breathing problems
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10
Q

What are the main triggers of fatal anaphylaxis?

A
  • Stings
  • Food (particularly nuts)
  • Antibiotics
  • Anaesthetic drugs
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11
Q

What is the treatment for anaphylaxis?

A

Intramuscular Adrenaline

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12
Q

How many epipens do people usually need to stop and reverse an anaphylactic shock?

A

2 doses

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13
Q

What is a wheal and flare reaction?

A

A skin prick test which tests for allergies.

A wheal and flare > 3mm is indicative of an allergy

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14
Q

What is the management of a patient with an allergy?

A
  • Allergen avoidance
  • Patient (+ parent) education
  • Medic alert ID
  • Drugs (ie anti-histamines, corticosteroids, epipen)
  • Allergen desensitisation (if high risk of anaphylaxis)
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15
Q

How soon do symptoms appear after a Type I hypersensitivity reaction is triggered?

A

< 30 mins

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16
Q

How soon do symptoms appear after a Type II hypersensitivity reaction is triggered?

A

5 - 12 hrs

17
Q
  • Drug-induced haemolytic anaemia
  • Granulocytopenia
  • Thrombocytopenia

are all types of what kind of hypersensitivity reaction?

A

Type II (antibody mediated) hypersensitivity reaction

18
Q

How soon do symptoms appear after a Type III hypersensitivity reaction is triggered?

A

3 - 8 hrs

19
Q
  • Systemic lupus erythematosus (SLE)
  • Aspergillosis
  • Rheumatoid arthritis

are all types of what kind of hypersensitivity reaction?

A

Type III (immune-complex mediated) hypersensitivity reaction

20
Q

How soon do symptoms appear after a Type IV (cell mediated) hypersensitivity reaction is triggered?

A

24-48 hrs

21
Q

A Tuberculin Mantoux reaction is what kind of hypersensitivity reaction?

A

Type IV (cell mediated) hypersensitivity reaction

22
Q

Why do westernised countries have an increasing prevalence of allergic disorders?

A
  • Small families (exposed to less antigens)
  • Stable intestinal flora
  • Increased antibiotic use
  • Reduced helminth burden
  • good sanitation education
  • reduced orofaecal burden

= TH2 phenotype = IgE production

23
Q

What type of T helper cells are usually produced by people in developing countries, compared to those in westernised countries? How does this affect the prevalence of allergic disorders?

A

Developing countries = TH1 phenotype
Westernised countries = TH2 phenotype

TH2 = IgE production = Mast cell degranulation = increased prevalence of allergic disorders in westernised countries

24
Q

Define atopy:

A

Genetic tendency to be ‘ hyperallergenic’

ESA3 (48 decks)

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