Pathophysiology of Asthma

Question 1

Basic pathology can be divided into 2 related components

Answer 1

1) An inflammatory/immune system component, in which the individual develops a hypersensitivity to a specific stimulus, causing an inflammatory response upon subsequent exposures to that stimulus.
2) An airway component, where the allergen-induced inflammation release mediators that affect cellular function, produce limitations in tissue function, resulting in the generation of symptoms (dyspnoea, excess mucus, and cough).

Question 2

Hagen Poiseuille

Answer 2

Airway radius decreases, the resistance increases dramatically

Question 3

Pathological changes in asthma

Answer 3

Primarily airway smooth muscle contraction and mucus hypersecretion which reduce the size of the airway lumen and therefore increases airway resistance and decreases airflow.

Majority asthma patients this is reversible

Question 4

Allergic asthma involves 2 stages

Answer 4

1) Sensitisation - where the immune system first encounters the allergen and develops an adaptive (antibody- and lymphocyte-mediated) immune response.
2) The allergic response - where the allergen is subsequently re-encountered, triggering the adaptive response previous primed during sensitisation. This generates an inflammatory response within the airways, producing symptoms.

Question 5

Sensitisation

Answer 5

• Allergen is inhaled and enters the airway tissue
• Allergen encountered by APCs to present to the adaptive immune system
• After engulfing and processing the allergen, the antigen is displayed externally so APC encounters a helper T cell
• T cell is activated and matures in Th2 cell
• Th2 cell interacts with a B cell to initiate proliferation and production of IgE antibodies
• IgE antibodies circulate and bind to receptor on mast cells

Question 6

Airway remodelling

Answer 6

• long term, negative structural changes that are irreversible
• can occur in patients with severe, poorly-controlled asthma, which results from repeated inflammation-induced tissue injury.

Question 7

What does airway remodelling involve

Answer 7

• A progressive and irreversible decline in airway and respiratory function
• Increase obstruction. And decrease FEV1
• Occurs in patients with severe, poorly controlled asthma

Question 8

Role of mast cells in asthma pathophysiology

Answer 8

Allergen induces degranulation - release inflammatory mediators

Question 9

Role of eosinophils in asthma pathophysiology

Answer 9

Chemokine induced degranulation - release of inflammatory mediators

Question 10

Inflammatory mediators produced by mast cells

Answer 10

Leukotrienes, prostaglandis

Question 11

Inflammatory mediators produced eosinophils

Answer 11

Reactive oxygen species, proteolytic enzymes, leukotrienes