Infection 9 - Allergies Flashcards Preview

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Flashcards in Infection 9 - Allergies Deck (24):
1

What is a hypersensitivity reaction?

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

2

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

Sensitization phase (1st encounter with antigen)

3

What is the most common hypersensitivity reaction 'allergies'?

Type I = IgE mediated

4

Which antibody mediates allergic reactions?

IgE

5

List some symptoms of a Type I 'allergic' hypersensitivity reaction:

- Urticaria
- Eczema
- Rhinitis
- Asthma
- Gastroenteritis
- Angioedema

6

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

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

7

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

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

8

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

Mast cell begins degradation, triggering:
- Release of Histamine and Chemokines
- Synthesis of Leukotrienes and Prostaglandins

= Increased vascular permeability, vasodilation, bronchoconstriction

9

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

Anaphylaxis
- hypotension
- angioedema
- general urticaria
- breathing problems

10

What are the main triggers of fatal anaphylaxis?

- Stings
- Food (particularly nuts)
- Antibiotics
- Anaesthetic drugs

11

What is the treatment for anaphylaxis?

Intramuscular Adrenaline

12

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

2 doses

13

What is a wheal and flare reaction?

A skin prick test which tests for allergies.
A wheal and flare > 3mm is indicative of an allergy

14

What is the management of a patient with an allergy?

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

15

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

< 30 mins

16

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

5 - 12 hrs

17

- Drug-induced haemolytic anaemia
- Granulocytopenia
- Thrombocytopenia

are all types of what kind of hypersensitivity reaction?

Type II (antibody mediated) hypersensitivity reaction

18

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

3 - 8 hrs

19

- Systemic lupus erythematosus (SLE)
- Aspergillosis
- Rheumatoid arthritis

are all types of what kind of hypersensitivity reaction?

Type III (immune-complex mediated) hypersensitivity reaction

20

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

24-48 hrs

21

A Tuberculin Mantoux reaction is what kind of hypersensitivity reaction?

Type IV (cell mediated) hypersensitivity reaction

22

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

- 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

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?

Developing countries = TH1 phenotype
Westernised countries = TH2 phenotype

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

24

Define atopy:

Genetic tendency to be ' hyperallergenic'