Allergies Flashcards

1
Q

What is an allergy?

A
  • Exaggerated immune response to a non-microbial/ environmental antigen.
  • Over production of immunoglobulin E (IgE).
  • Involve cytokines IL-4,5 & 13 produced by Th2 cells, IgE, mast cells and eosinophils.
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2
Q

What is atopy?

A

Genetically determined, exaggerated IgE-mediated immune response
- Type 1 hypersensitivity disorders e.g. hay-fever, asthma

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3
Q

What are the types of allergic disease?

A

Asthma, rhinitis, urticaria & angioedema and eczema

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4
Q

What is asthma?

A

Chronic disorder of airways with variable airflow limitation.
- Recurrent episodes of wheezing, breathless, tight chest, cough.
- Inhaled allergen - most common

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5
Q

What is rhinitis?

A

Respiratory disease linked with asthma
- Nasal congestion ,itching and sneezing

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6
Q

What is urticaria and angioedema?

A

Raised, itchy nettle rash - like hives
- Triggers; food and drug allergens e.g. NSAIDs, ACEIs

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7
Q

What is eczema?

A

Local inflammation of the skin
- appears in early childhood induced by food e.g. eggs, milk

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8
Q

Describe anaphylaxis.

A

Severe allergic reaction - life threatening/ death
Systems involved; respiratory, blood, cardio and gastro
Allergen triggers; food, drugs - antibiotics, venoms latex

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9
Q

Describe genetic predisposition.

A
  • Influenced by inheritance of several genes/chromosomes.
  • Identification of susceptibility locus for atopy on chromosomes 5q, near site of gene cluster encoding cytokines IL-4,5,9 &13
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10
Q

What is the hygiene hypothesis?

A

Cleaner environment = less microbes

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11
Q

Describe the skin prick test.

A
  1. Gold standard method - drop of allergen on skin, small skin prick, skin reaction - local tissue swelling and degranulation.
  2. Test selection of allergens according to clinical history.
  3. Pt must not be taking antihistamines as it will diminish sensitivity of test - false negative.
  4. Controls; histamines (+ve), saline (-ve).
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12
Q

Describe allergen sensitisation.

A

Exposure to an allergen leads to IgE production which results in 2 events.
- Differentiation of Tcells to Th2
- Stimulate B cells to switch to IgE production - Th2 cells produce cytokines and provide CD40 ligand to lead antibody class switching.

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13
Q

What are the roles of mast cells and basophils?

A

Initiate acute inflammatory response
Basophils - reside in circulation
Mast cells - function as immune sentinel cells and produce cytokines.

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14
Q

Where are mast cells found?

A

In connective tissue surrounding blood vessels and mucosal surfaces.

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15
Q

What is the granule contents of mast cells?

A

Histamine
Leukotrienes
Inflammatory cytokines
Neutrophil and eosinophil attracting cytokines

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16
Q

What is the granule contents of eosinophils?

A
  • T and B cell attracting chemokines
  • Fibrotic cytokines
  • Matrix metalloproteinases and collagenases
17
Q

What is the early phase of allergic response?

A
  • Physiological mechanisms
  • Loss of organ function due to; mucus production, vasodilation and swelling, bronchoconstriction.
18
Q

What is the late phase response of allergic response?

A
  • Immunological mechanisms
  • Smooth muscle scarring
  • Recruitment of immune cells into peripheral tissues
19
Q

What is the immediate phase response of allergy?

A
  • Mast cell degranulation
  • Histamine release
20
Q

What is the late phase allergy response?

A
  • Immune response
  • Eosinophil migration