Asthma and Respiratory Immunology Flashcards

1
Q

How many people are currently receiving treatment for asthma?

A

5.4 million people in the UK

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2
Q

How many children are affected by asthma?

A

1.1 million children affected (approx. 3 in every class)

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3
Q

How many people die of an asthma attack every day in UK?

A

On average, 3 people die of an asthma attack every day in the UK

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4
Q

How much does the NHS spend on asthma?

A

NHS spends approx. £1billion annually treating asthma

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5
Q

What are the cardinal features of asthma?

A
  • Wheeze +/- Dry cough – on exertion, worse with colds, with allergen exposure: most important
  • Atopy / allergen sensitisation
  • Reversible airflow obstruction
  • Airway inflammation
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6
Q

What causes airway inflammation?

A
  • Eosinophilia

* Type 2 - lymphocytes

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7
Q

Why do only some people who are sensitized develop disease (asthma)? What are these manifestations of asthma?

A
  • genetic susceptibility and environmental exposures:
    1. Allergy
    2. Reversible airflow obstruction
    3. Inflammation
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8
Q

What can genetic susceptibility lead to?

A
  • Allergy
  • Allergic disease
  • Need genetic susceptibility for asthma not guaranteed with just an allergy
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9
Q

What are some environmental exposures?

A
  1. Allergen
  2. Infection that causes colds
  3. Pollution
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10
Q

What is the test for allergic sensitisation?

A
  1. Blood tests – for specific IgE antibodies to allergens of interest
  2. Total IgE alone not sufficient to define atopy - need specific IgE
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11
Q

What are the tests for eosinophilia?

A
  1. Blood eosinophil count when stable: >300 cells /mcl is abnormal during stable disease
  2. Induced sputum eosinophil count: >2.5% eosinophils is abnormal
  3. Exhaled nitric oxide
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12
Q

How is fractional concentration of exhaled nitric oxide (FeNO) used?

A
  1. quantitative
  2. non-invasive
  3. safe
  4. method of measuring airway inflammation
  5. an indirect marker of T2-high eosinophilic airway inflammation in asthma
    - So high NO then supportive of asthma provided not on treatment with steroids
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13
Q

How else is FeNO used?

A
  1. aiding asthma diagnosis
  2. predicting steroid responsiveness and assessing adherence to inhaled corticosteroids
    - So if started treatment but NO still sky high suggests not taking as NO very sensitive to steroids
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14
Q

What parts of clinical assessment is needed for asthma diagnosis?

A
  1. History & examination

2. Assess / confirm wheeze when acutely unwell

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15
Q

What are the objective tests for asthma diagnosis?

A
  1. Airway obstruction on spirometry - FEV1/FVC ration <0.7
  2. Reversible airway obstruction - Bronchodilator reversibility >12%
  3. Exhaled nitric oxide (FeNO) >35ppb (children), >40ppb (adults) - not on any treatment
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16
Q

What other condition other than symptoms suggestive of asthma to diagnose asthma in children and young people (aged 5to16)?

A
  1. FeNO level of 35ppb or more and positive peak flow variabilityor
  2. Obstructive spirometry and positive bronchodilator reversibility
    - need two tests!
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17
Q

How do you reduce airway eosinophilic inflammation in the management of asthma?

A
  1. Inhaled corticosteroids (ICS)

2. Leukotriene receptor antagonists - reduce T2 inflammation

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18
Q

How do you manage acute symptomatic relief in management of asthma?

A
  1. Beta-2 agonists (smooth muscle relaxation)

2. Anticholinergic therapies (smooth muscle relaxation)

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19
Q

How do you manage severe asthma (steroid sparring therapies) in the management of asthma?

A
  1. Biologic targeted to IgE
    - Anti-IgE antibody
  2. Biologics targeted to airway eosinophils
    - Anti-interleukin-5 antibody
    - Anti-interleukin-5 receptor antibody
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20
Q

Which structural cells do corticosteroids affect?

A
  1. Epithelial cell
  2. Endothelial cell
  3. Airway smooth muscle
  4. Mucus gland
21
Q

Which inflammatory cells do corticosteroids affect?

A
  1. Eosinophil
  2. T-lymphocyte
  3. Mast-cell
  4. Macrophage
  5. Dendritic cell
22
Q

What is the airway like in asthmatics?

A
  1. Laminar flow in normal person and with asthmatic even when well but not on treatment airway looks abnormal
  2. thickened airway wall (caused by inflammation) and baseline increase in airway smooth muscle, but if treated should look all normal
23
Q

Why do asthmatic wheeze?

A

due to narrowed airway lumen resulting in turbulent flow through airways

24
Q

What lung function test is carried out to see reversible airway obstruction?

A

Spirometry lung function test

25
Q

What is the pathogenesis of asthma?

A

If exposed to allergens and sensitised then will develop inflammation and airway remodelling

26
Q

What is examples of airway remodelling in pathogenesis of asthma?

A
  1. recruitment of inflammatory cells into airway (predominantly eosinophils)
  2. structural changes include changes in epithelium
    - increased goblet cells
    - amount of matrix increases
    - amount and size of smooth muscle increase
27
Q

How do we know about genetic susceptibility for asthma?

A
  • GWAS studies e.g. iL-33 gene increased in asthma and GSDMB
  • Manhattan plot looks at chromosome where gene is and p value tells how likely it is that gene increased normally and then look at disease
  • Log P value so has to be very high P value to be significant
28
Q

Is asthma a single gene disorder?

A

No - multigene and polyfactorial (so gene therapy can’t really be used, but looking for genes for novel therpaies)

29
Q

How does asthma manifest?

A
  1. In asthma exposed to inhaled allergen (antigen) which is presented to antigen presenting cells (APC) (dendritic cells for lungs)
  2. Which carry the antigen via MHC class II to lymph nodes in mediastinum where naive T helper cells (Th0) differentiate into Th2 cells
30
Q

What does the Th2 cells secrete?

A

Il-4, Il-5 and Il-13

31
Q

What does Il-4 do?

A

helps conversion of plasma cells (B cells0 to secrete Ig-E

32
Q

What does Il-5 do?

A

recruits eosnphil into airway and promotes eosinophil survival

33
Q

What does Il-13 do?

A

mucus secretion

34
Q

What happens when you are exposed to the same allergen again?

A

build an allergic immune response which means that allergen is recognised by IgE

35
Q

What does the IgE do?

A

binds to mast cells which release various growth factors, cytokines, chemokine when they degranulate which results in allergic reaction e.g. histamines and type 2 mediators are released so final allergic reaction

36
Q

What is a skin prick test for allergies?

A
  • Intradermal injection of positive control (histamine) which we all react to compared
  • to saline which is a negative control
  • compare that to allergens e.g. pollen, grass
37
Q

What will the skin prick show if the patient is sensitised?

A

develop and wheel and flare reaction (like stinging nettle reaction) and measure size of wheel to determine other they are sensitised to that allergen

38
Q

How do corticosteroids affect eosinophils?

A

Decrease numbers by apoptosis

39
Q

How do corticosteroids affect T-lymphocytes?

A

Decrease cytokines

40
Q

How do corticosteroids affect mast cells?

A

Decreased numbers

41
Q

How do corticosteroids affect macrophages?

A

Decrease cytokines

42
Q

How do corticosteroids affect dendritic cells?

A

Decrease numbers

43
Q

How do corticosteroids affect epithelial cells?

A

Decrease cytokines + mediators

44
Q

How do corticosteroids affect endothelial cells?

A

Decrease leak

45
Q

How do corticosteroids affect airway smooth muscle?

A

Increase Beta 2 receptors

Decrease cytokines

46
Q

How do corticosteroids affect mucus glands?

A

Decrease mucus secretion

47
Q

What is the main aim of using corticosteroids?

A

Target T2 inflammation and reduce that

48
Q

What is the most important aspect of asthma management?

A
  1. Optimal device and technique
  2. Clear asthma management plan
  3. Adherence to inhaled corticosteroids