Lung Immunology Flashcards
What are the allergic airway diseases?
Upper airways = allergic rhinitis
Bronchi = asthma
Alveoli = allergic alveolitis
How is hypersensitivity divided?
Immunological (Allergy):
IgE-mediated (Atopic diseases) = hay fever, eczema, asthma.
Non IgE-mediated = farmer’s lung.
Non-immunological:
Pharmacological = aspirin hypersensitivity.
Enzyme deficiency = lactate dehydrogenase deficiency.
Intolerance = food.
Define allergy
Exaggerated immunological response to a foreign substance which is either inhaled, swallowed, injected, or comes in contact with the skin or eye.
MECHANISM, not a disease.
What causes the acute and chronic symptoms of allergy?
Acute = caused by IgE coating mast cells which results in mast cell degranulation.
Chronic = Th2 cells releasing cytokines and chemokines.
Th1 or Th2
Th1 cells (+ Th17, NK, CD8, IgM, IgA, IgG): Viruses, bacteria, fungi, protozoa.
Th2 cells (+ IgE, IgG1, innate lymphoid cells, eosinophils, mast cells, basophils, activated macrophages): Helminths, ectoparasites.
What do the Th2 cell’s cytokines do?
IL-4 -> IgE synthesis
IL-5 -> Eosinophil development
IL-9 -> Mast cell development
IL-13 -> IgE synthesis and airways hyper-responsiveness
Define atopy and give examples of atopic diseases
Hereditary predisposition to produce IgE antibodies against common environmental allergens.
(Tissue reactions are characterised by infiltration of Th2 cells and eosinophils).
Atopic diseases = allergic rhinitis, asthma, atopic eczema.
What is the allergic march?
Term that describes the common progression of atopic diseases from atopic dermatitis to allergic asthma - however, it is probably wrong because it’s not observable at an individual level.
What is rhino-conjunctivitis?
Affects UPPER AIRWAYS like the nose in up to 17% of the population - the seasonal allergic version is summer hay fever.
Common causes are house dust mite, cats, dogs, cockroaches, horses.
What is asthma?
Affects LOWER AIRWAYS like trachea and bronchi in 8-12% of the population.
Heterogenous disease - many phenotypes:
Based on control/severity = intermittent, persistent, chronic/severe.
Based on endotype or endophenotype = allergic/atopic/eosinophilic asthma, neutrophilic asthma, exercise-induced asthma.
Atopy can be assessed using skin prick tests.
What is extrinsic allergic alveolitis?
Affects DISTAL AIRWAYS in 0.1% of the population - it is a pulmonary hypersensitivity disorder but not atopic.
Small allergenic particles enter distal airways which stimulates inflammatory cells and factors in the pulmonary capillaries.
E.g. farmer’s lung, bird fancier’s lung, mushroom worker’s lung, air conditioner lung.
What is general anaphylaxis?
Systemic allergic reaction which causes dizziness, seizures, laryngeal oedema, bronchoconstriction, arrhythmia, anxiety, vomiting and diarrhoea.
It is caused by drugs, foods, insect stings, latex.
What is the hygiene hypothesis?
The germ free environment in the industrialised society has led to the Th2 response which occurs in asthma.
Childhood exposure to germs allows the immune system to develop and differentiate between harmless and harmful substances.
Farming environments confer protection against the development of allergy.
What factors are associated with allergy and asthma prevalence?
Microbial: water sanitation, food quality (lack of fermenting bacteria), poverty, medical interventions.
Non-microbial: pollution, diet and nutrition (lack of vitamin D, omega 3 fatty acids, fish oil), obesity (may cause chronic inflammation), climate change (pollen), stress, genetics.
Treatment of allergic diseases?
Allergen avoidance
Anti-allergic medication.
Immunotherapy.
Allergen-injection immunotherapy can be effective and produce long lasting immunity BUT there is the occasional severe allergic reaction, standardisation problems and it’s time consuming.
