Lecture 7: Asthma Flashcards
Describe the mechanism of type I IgE-mediated hypersensitivity reactions in asthma.
During first exposure, allergen activates the TH2 cell and induces IgE class switching in B cells. The activated B cells then secretes the IgE molecules, where it binds to FcεRI on mast cells (priming).
During subsequent exposures, the allergen now activates the mast cell, which releases mediators such as histamines.
Evaluate precipitating factors and triggers in asthma
Critically summarise the genetic and environmental factors associated with asthma.
- genetic predisposition to atopy (type I hypersensitivity)
- very complex interplay between genetic and environmental factors
- 100 genes implicate - susceptibility loci on long-arm of chromosome 5 (5q)
- ADAM-33 polymorphisms - MMP involved in bronchial hyperresponsiveness
- non-allergic asthma
- no evident family hsitory
- usually occupational by nature
Discuss principles of pharmacological management of asthma.
Majority of cases managed with:
- short-acting ß2-agonist (smooth muscle relaxer)
- low-dosed inhaled corticosteroid
- works on various pathways of inflammation
- reduced effects of inflammation
Recall the diagram of the types of chronic obstructive pulmonary disease.
Describe emphysema.
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath due to over-inflation of the alveoli. Therapy to provide relief of symptoms, prevent complications and slow the progression of disease.
Describe chronic bronchitis.
Chronic bronchitis involves persistent coughs with sputum production for at least 3 months in 2 consecutive years. It may progress to COPD and may overlap with emphysema.
Hypersecretion of mucus and if persistent marked increase in goblet cells in small airways. Treatment with mucolytics
What is asthma?
Asthma is a chronic disorder of the conducting airways, usually caused by an immunological reaction, which is marked by episodic bronchoconstriction. Involves increased airway sensitivity to a variety of stimuli, inflammation of the bronchial wall, and increased mucus secretion.
Recall the types of asthma.
How do you diagnose asthma?
- Symptoms:
- persistent cough
- wheezing (stethoscope)
- shortness of breath
- spirometry
- FEV (Forced Expiratory Volume)
- Methacholine challenge - stimulates the parasympathetic nervous system - bronchial hyperactivity
Recall the mediators released after mast cell activation by allergen.
Recall the following events after the activation of the helper T cell by APC.
Compare between the normal airway and airway in asthma.
- Thickened basement membrane
- Increased mucus in the bronchial lumen
- Goblet cell hyperplasia
- Hypertrophy of submucosal glands
- Hypertrophy/hyperplasia of smooth muscle cells
- Damage to the epithelium
Recall the late asthmatic response diagram.
