Allergies Flashcards Preview

[ ESA 3- Infection and Immunity > Allergies > Flashcards

Flashcards in Allergies Deck (95):
1

What does the term hypersensitivity describe?

The antigen specific responses that are either inappropriate or excessive, and result in harm to host

2

What mechanisms underlie the hypersensitivity immune responses?

Those employed by the host to fight infections

3

What are the common features of hypersensitivity responses?

Sensitisation phase
Effector phase

4

What happens in the sensitisation phase of a hypersensitivity response?

First encounter with antigen

5

What happens in the effector phase of a hypersensitivity response?

Clinical pathology upon re-exposure to same antigen

6

What are the types of hypersensitivity reactions?

Type I, or immediate
Type II, or antibody mediated
Type III, or immune complex mediated
Type IV, or cell mediated

7

How quick is the onset of type I hypersensitivity reactions?

<30 minutes

8

What are type I hypersensitivity reactions also known as?

Allergies

9

What are type I hypersensitivity reactions a response to?

Environmental non-infectious agents (allergens)

10

What molecule do type I hypersensitivity reactions involve?

IgE

11

When is the onset of type II hypersensitivity reactions?

5-12hrs

12

What are type II hypersensitivity reactions a response to?

Non-soluble tissue antigens

13

What molecule do type II hypersensitivity reactions involve?

IgG

14

When is the onset of type III hypersensitivity reactions?

3-8hrs

15

What are type III hypersensitivity reactions a response to?

Soluble antigens

16

When is the onset of type IV hypersensitivity reactions?

24-48hrs

17

What is a type IV hypersensitivity reaction a response to?

Environmental infectious agents and self antigens

18

What kind of diseases are type IV hypersensitivity reactions?

Autoimmune diseases

19

What is happening to the worldwide prevalence of allergies?

It is increasing

20

How does the incidence of allergy in the UK compare to other countries?

It is in the top 3 countries with the highest incidence of allergy

21

What % of children in the UK have an allergy?

>50%

22

How many <45 year olds have 2 or more allergies in the UK?

13 million

23

What proportion of children have a peanut allergy in the UK?

1 in 50

24

How much do allergies cost per year in primary care in the UK?

£900 million

25

What is the development of allergy thought to be affected by?

A mixture of genetics and environmental factors

26

What phenotype often present as non-allergic?

TH1

27

What phenotype often presents as allergic?

TH2

28

How is geographical location related to allergy?

Those from developing countries tend to have less allergies, and those from westernised countries tend to have more allergies

29

Why do people from developing countries tend to have less allergies?

Large family sizes
Rural homes, lifestock
Intestinal microflora variable/transient
Low antibiotic use
High helminths burden
Poor sanitation, high orofecal burden

30

Why do those from westernised countries tend to have more allergies?

Small family size
Affluent, urban homes
Intestinal microflora stable
High antibiotic use
Low or absent helminths burden
Good sanitation, low orofecal burden

31

What are the common allergies?

House dust mite, cockroaches
Animals
Tree and grass pollen
Insect venom
Medicines
Chemicals
Foods

32

What animals are people commonly allergic too?

Domestic pets such as cats and dogs

33

What insect venoms are people commonly allergic too?

Those contained in wasp and bee stings

34

Give an example of medicines people are commonly allergic too

The antibiotic penicillin

35

Give an example of a chemical people are often allergic too

Latex

36

What foods can people be allergic too?

Milk
Eggs
Wheat
Peanuts
Tree nuts
Seafood

37

What should be considered with people with allergies?

People with allergies can often have cross-reactions with other associated allergens

38

What are hypersensitivity reactions caused by?

Activation of mast cells through IgE dependant mechanisms

39

What is the result of activation of mast cells in hypersensitivity?

These activated mast cells then release chemical mediators

40

What is the most important chemical mediator in hypersensitivity reactions?

Histamine

41

What are the classes of chemical mediators in hypersensitivity reactions?

Enzymes
Toxic mediator
Cytokine
Chemokine
Lipid mediator

42

Give 4 examples of enzyme chemical mediators in hypersensitivity reactions

Tryptase
Chymase
Cathpepsin G
Carboxypeptidase

43

What are the biological effects of enzyme chemical mediators in hypersensitivity reactions?

Remodel connective tissue matrix

44

Give two examples of toxic mediators in hypersensitivity reactions

Histamine
Heparin

45

What are the biological effects of toxic mediators in hypersensitivity reactions

Toxic to parasites
Increase vascular permeability
Cause smooth muscle contraction

46

Give 6 cytokine chemical mediators in hypersensitivity reactions

IL-4
IL-13
IL-3
IL-5
GM-CSF
TNF-alpha

47

What are the biological effects of IL-4 and IL-13 in hypersensitivity reactions?

Stimulate and amplify TH2 cell response

48

What are the biological effects of IL-3, IL-5, and GM-CSF in hypersensitivity reactions?

Promote eosinophil production and activation

49

Where does the TNF-alpha in hypersensitivity reactions come from?

Some stored preformed in granules

50

What are the biological effects of TNF-alpha in hypersensitivity reactions?

Promotes inflammation
Stimulates cytokine production by many cell types
Activates endothelium

51

What chemokine chemical mediator is released in hypersensitivity reactions?

CCL3 (MIP-1alpha)

52

What are the biological effects of chemokines in hypersensitivity reactions?

Attracts monocytes, macrophages, and neutrophils

53

Give 4 lipid mediators in hypersensitivity reactions

Leukotrienes C4, D4, E4
Platelet-activating factor

54

What are the biological effects of leukotrienes in hypersensitivity reactions?

Cause smooth contraction
Increase vascular permeability
Stimulate mucus secretion

55

What are the biological effects of platelet-activating factor in hypersensitivity reactions?

Attracts leukocytes
Amplifies production of lipid mediators
Activates neutrophils, eosinophils, and platelets

56

What does an initial exposure to an allergen cause?

Plasma cells to create an antigen-specific IgE

57

What happens once an antigen-specific IgE has been produced?

It binds to mast cells to sensitise it to the specific antigen (allergen)

58

What does second exposure to an allergen cause?

Cross-linking of the IgE molecules on the surface of the mast cell

59

What does cross linking of IgE molecules on the mast cell trigger?

The release of granule contents, including histamine and chemokines, and synthesis of new mediators; leukotrienes and prostaglandins

60

What does the release of granule contents from mast cells result in?

A number of physiological changes, such as;
Increased vascular permeability
Vasodilation
Bronchoconstriction

61

How is an allergic reaction diagnosed?

Blood/serum levels of mast cell products

62

Where can the effects of an allergic reaction manifest?

The epidermis
Deep dermis

63

How can the effects of allergic reaction manifest in the epidermis?

Increased vascular permeability and vasodilation results in urticaria (hives)

64

How does urticaria present?

Creates a wheal and flare type marking on the skin

65

How can the effects of an allergic reaction manifest in the deep dermis?

Increased vascular permeability and vasodilation results in angiodema of the lips, eye, tongue, and upper respiratory tract

66

What is the problem with the manifestation of allergic reaction in the deep dermis?

It can carry the risk of suffocation if in the respiratory tract

67

What can systemic activation of mst cells result in?

Anaphylaxis

68

How serious is anaphylaxis?

Medical emergency- death if not treated

69

What happens in anaphylaxis?

Increased vascular permeability leads to hypotension and cardiovascular collapse
Generalised urticaria and angiodema
Bronchoconstriction leads to breathing problems

70

How many deaths did anaphylaxis result in between 1992 and 2001?

Over 200 but im pretty sure this isnt going to be in the exam so its a pointless fact

71

When should anaphylaxis be treated?

Immediately

72

How should anaphylaxis be treated?

Intramuscular adrenaline

73

What is the effect of intramuscular adrenaline in anaphylaxis?

Reverses peripheral vasodilation and reduces oedema
Alleviates hypotension
Reverses airway obstruction/bronchospasm
Increases force of myocardial contraction
Inhibits mast cell activation

74

Why is adrenaline said to be a time-saver rather than a life-saver in anaphylaxis?

Reactivation can re-occur in 20% of patients without re-exposure to the antigen

75

What may be required with adrenaline in anaphylaxis?

Multiple doses

76

What is required with adrenaline in anaphylaxis?

Proper use of the epipen

77

What is it important to do after treatment with adrenaline in anaphylaxis?

Continue to monitor pulse, BP, ECG, and O2 sats

78

What factors are considered in a diagnosis of allergy?

Clinical history
Blood tests
Skin prick tests
Challenge tests

79

What clinical history is considered in allergy?

Atopy
Allergens
Seasonalities
Route of exposure

80

What blood tests are done in diagnosis of allergy?

Serum allergen-specific IgE
Serum mast cell tryptase, histamine (systemic granulation)

81

What allergens are skin prick tests done for?

Range of allergens

82

What is being looked for in skin prick tests?

Wheat and flare reaction of >3mm

83

What do skin prick tests need?

Trained personnel

84

When is a challenge test done?

Food and drug allergy

85

What is the problem with challenge tests?

Slight risk of anaphylaxis on highly sensitised patients

86

How is an allergy managed?

Allergen avoidance/elimination
Education
Medic alert information
Drugs
Allergen desensitisation

87

How can allergens be avoided/eliminated?

Read food levels
House dust mite avoidance
Avoid high risk situations

88

What education is given in management of allergy?

Parents to recognise symptoms
Patients to use epipen
Call emegency devices when epipen is used
Schools and social activities

89

What drugs can be given in the management of allergy?

Antihistamines
Corticosteroids
Anti-IgE IgG
Anaphylaxis

90

What should be given in antihistamine prevention?

Alternating sedating/non-sedating forms

91

How can corticosteroids be administered in allergy management?

Topical
Systemic

92

Give an example of an anti-IgE IgG drug

Omalizumab

93

What does allergen desensitisation involve?

Administration of increasing doses of allergen extracts over a period of years

94

When is allergen desensitisation used?

In patients with high risk of systemic attack

95

Under what conditions must allergen desensitisation take place?

In a specialist hospital based unit with resuscitation equipment