1.2.1 Type I Hypersensitivity Reactions Flashcards

1
Q

What is a type 1 hypersensitivity reaction?

A

Allergy

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2
Q

What are the 3 features of type 1 HSRs?

A

Immunological basis for different diseases
-Different organs affected

Immediate reaction
-Local reaction: ingested or inhaled allergen
-Systemic reaction: insect sting or IV administration

Antigens
-Allergens, environmental, non-infectious antigens (proteins)

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3
Q

What are the 3 different types of allergen exposure?

A

Seasonal
Perennial
Accidental

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4
Q

Give an example of a seasonal allergen exposure

A

Tree and grass pollens

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5
Q

Give examples of perennial allergen exposures

A

House dust mite
Animal dander- cats and dogs
Fungal spores

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6
Q

Give examples of accidental exposure allergens

A

Insect venom- wasp and bee stings
Medicines- penicillin
Chemicals- latex
Foods- milk, peanuts, nuts, shellfish etc.

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7
Q

What is a cross reaction?

A

Foods/substances which have a similar structure to something that you are allergic to, which will cause you to have an allergic reaction

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8
Q

What are the two mechanisms of T1HSRs?

A

Abnormal adaptive immune response against the allergens

Mast cell activation

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9
Q

Outline the abnormal adaptive immune response against allergens mechanism

A

T helper 2 (TH2) response (IL,4,5 and 13)
IgE production

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10
Q

Outline the mast cell activation mechanism

A

Sensitised individuals
Different clinical allergic disorders depending on location of mast cell

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11
Q

Why are people with westernised lifestyles more susceptible to allergies?

A

Due to less exposure to allergens

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12
Q

What is the hygiene hypothesis?

A

Children exposed to animals, pets and microbes in the early postnatal period appear to be protected against certain allergic diseases

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13
Q

What is microbial dysbiosis?

A

Alteration of the symbiotic relationships with parasites and bacteria causing compositional and functional alterations of the microbiome

Associated with western lifestyle due to reduced exposure to bacteria

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14
Q

What is the impact of microbial dysbiosis on diseases?

A

Increased:
- Immune diseases
- Metabolic diseases
- Autism
- Colorectal cancer

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15
Q

What two ways can mast cells become activated?

A

IgE- dependent mechanism

Non-IgE dependent mechanism

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16
Q

What is the strategic location of mast cells?

A

Most mucosal and epithelial tissues

e.g. GI tract, skin, respiratory epithelium

Connective tissue surrounding blood cells

17
Q

What is the role of mast cells?

A
  • Activation of effector cells- T cells, neutrophils etc.
  • Direct antimicrobial effect
  • Recruitment of effector cells
  • Physiological tissue remodelling e.g. pregnancy
  • Angiogenesis regulation- formation of blood vessels
18
Q

What are the 4 main mast cell mediators?

A

Tryptase
-Enzyme

Histamine
-Toxic mediator

Leukotrienes C4,D4,E4
-Lipid mediator

Platelet-activating factor
-Lipid mediator

19
Q

What is the biological effect of tryptase?

A

Enzyme class

Remodels connective tissue matrix

20
Q

What is the biological effect of histamine?

A

Toxic mediator class

Toxic to parasites
Increases vascular permeability
Causes smooth muscle contraction

21
Q

What are the biological effects of leukotrienes C4,D4 and E4?

A

Lipid mediator class

Cause smooth muscle contraction
Increases vascular permeability
Stimulates mucus secretion

22
Q

What is the biological effect of platelet-activating factor?

A

Lipid mediator class

Cause smooth muscle contraction
Increases vascular permeability
Stimulates mucus secretion