Lecture 12 - Asthma Flashcards
What is asthma?
The chronic inflammation of the airways causing REVERSIBLE airway obstruction
What are the 4 main symptoms associated with asthma?
Wheeze
Cough
Chest tightness
Breathlessness
Why can bronchiospasm occur in patients with asthma?
The patients have an increased airway responsiveness to stimuli, if stimuli occurs bronchoconstriction happens
What is meant by asthma exacerbation?
When there are periods of increased symptoms
Why is it thought that asthma is more prevalent in high income countries?
Better access to health care
Better diagnostic processes
Different climates (colder?)
More dust/air pollutants?
What is the pathophysiology of the airways in asthma?
During normal period:
During an asthma attack/exacerbation:
Inflammation and thickening of the smooth muscle and thickening of the epithelial layer which narrows the air way
In an attack the smooth muscle constricts (Bronchoconstriction) which significantly narrows the airway
What increases your risk of having asthma?
Genetic susceptibility (Mainly inherited from Mothers side)
Atopy
Sensitisation to an allergen
What are the 3 atopic conditions?
Eczema
Hay fever
Asthma
What is the triad of things that occur in the airways that all contribute to each other?
Airway inflammation
Airway hyper responsiveness
Airway remodelling
What are the 2 phases in the immune response in asthma?
Immediate response Type I hypersensitivity
Late phase response Type IV hypersensitivity
What cells are involved in the Type I hypersensitivity stage/sensitisation stage of asthma?
APC (like a macrophage)
Th2 (T-Helper cell 2)
B cells
Plasma cells
Mast cells or basophils
What is the end result in the Type I hypersensitivity phase?
Bronchoconstriction
Describe what happens in the Type I hypersensitivity stage of asthma:
First exposure to allergen
Allergen encounters APC (phagocytosed) and its antigen displayed on APC
Antigen of allergen activates Th2
Th2 activates B cell to stimulate plasma cell to produce IgE to that allergen
IgE then taken up by the inflammatory mast cells and basophils
When the allergen is reintroduced from the body, the allergen binds to the IgE now on the mast cells, this leads to mast cell degranulation leading to substances being released that cause bronchoconstriction
What is released by the degranulation of the mast cells in Type I hypersensitivity in asthma that leads to bronchoconstriction?
Histamine
Leucotrienes
Other inflammatory mediators
What are the 2 main types of asthma?
Eosinophilic/allergy asthma
Non allergic eosinophilic inflammation
What is the main interleukin produced that stimulates eosinophilic activity?
IL-5
What is the process that occurs in Eosinophilic asthma (atopic) in Type IV hypersensitivity?
Allergens in bronchiole
APC
T cell activates B-cells(Type I hypersensitivity)
T cell makes IL-5 which affects eosinophils increasing bone marrow production nd causing them to migrate to the airways
In the airways the eosinophils produce cytokines and other inflammatory mediators maintaining the inflammation
What is the key difference between eosinophilic asthma and non-allergic eosinophilic inflammation/asthma?
Eosinophilic asthma involves activation of Th2
Non-allergic eosinophilic inflammation/asthma doesn’t involve Th2 and doesn’t involve allergens
What is usually the trigger in the bronchioles leading to eosinophils moving into the airways in no-allergic eosinophilic inflammation?
Pollutants
Microbes
What is meant by the airways being hyper responsive in asthma?
The inflammation makes the airway more reactive meaning stimuli that are non allergen can trigger bronchoconstriction