Allergy In The Lung Flashcards
What is intolerance?
Inability to cope with normally acceptable conditions/exposures
Describe the potential mechanisms of intolerance
- trigger (first exposure = no reaction, but future responses decided)
- immediate: recognition by APC + T cells, mediated by IL-4 + IL-33, response carried out by IgE and mast cells
- delayed: recognition by APC + T cells, mediated by IL-12 + IFN gamma, response carried out by reactive T cells
Describe the features of allergy
- clinical reaction (acute - sudden and short lived, or chronic - slow and progressive)
- immune system intolerance (requires response to a trigger, memory, characteristic clinical features depending of which arm of the immune system activated)
- chronic allergy leads to tissue remodelling
What are the differences in allergy to hypersensitivity
- does not have dose dependency (only show slight changes)
- same reaction to the trigger
How does an allergy affect the airways and lung parenchyma?
Airways:
- increases resistance to airflow
- causes wheeze/stridor (turbulence)
- measured by spirometry
Parenchyma:
- affects gas transfer and compliance
- CXR/imaging helpful
What are the clinical consequences of lung allergies?
- medium and small airway walls are flaccid as they are not supported by cartilage
- allergy causes the airways to collapse on expiratory phase due to narrowing
- muco-ciliary clearance impaired causing increased sputum
- CXR unhelpful
What are the pathological aspects of asthma?
- inflammation
- scabby epithelium
- thickened BM
- thickened smooth msucle
What are the physiological aspects of asthma?
- yellow mucus
- repair pathways
- non-elastic airways
- increased responsiveness
- increased sensitivity
What are the clinical components of asthma?
- cough
- wheeze
- hyper-reactivity
- hyper-sensitivity
What is asthma?
Reversible airflow obstruction
What are physiological tests you can do for asthma?
- peak flow
- spirometry
- plethsymography box (can be used to determine triggers)
What cells mediate airway inflammation in asthma?
Eosinophils
What cells are involved in asthma?
- mast cells
- lymphocytes
- macrophages
- epithelial cells
Describe the process of airway remodelling in asthma
- angiogenesis
- epithelial cell damage
- fibrosis
- smooth muscle hypertrophy
Describe the possible specifically targeted treatments for asthma
- anti-IgE biological therapy (targets IgE)
- corticosteroids (targets mast cells, macrophages and smooth muscle)
- anti-leukotriene receptor drugs (targets macrophages and smooth muscle)
- bronchodilators (targets smooth muscle and autonomic nerve)
Describe the mechanism of allergic disease in lung parenchyma
- delayed immune response
- re-exposure = intolerant systemic reaction
- mediated by IgG and antigens forming an immune complex
- tissue remodelling
Describe the signs and symptoms of acute illness associated with lung parenchyma allergy
- 4-6hrs after exposure
- wheeze, cough, fever, chills, headache, myalgia, malaise, fatigue
- can last several days
- serum sickness
What cells are involved in lung parenchyma allergy?
Neutrophils
What are the clinical consequences of lung parenchyma disease?
- thickening of septae, filling of alveolus with fluid
- loss of O2 (hypoxaemia - normal CO2) and reduced O2 transport into bloodstream
- air space shadowing on CXR
What is the effect of chronic allergen exposure to lung parenchyma?
- fibrosis: interstitial scarring from chronic tissue remodelling/repair pathways
- emphysema: interstitial destruction from neutrophilic enzyme release and reduced surface area
What is extrinsic allergic alveolitis?
- acute illness = type 3 reaction (serum sickness/immune complex disease)
- subacute illness (days-weeks) = type 4 T cell-mediated reaction (chronic dermatitis of lung)
- chronic disease = fibrosis and emphysema
What is the management of allergy in the lung?
- avoid triggers
- corticosteroids for inflammation (neutrophils can be responsive, cytotoxics)
- O2 supplementation
