Resp 13 - lung immunology - allergic airway disease Flashcards
Which allergic disease affects the upper airways, the bronchi and the alveoli?
upper airways -> allergic rhinitis
the bronchi -> asthma
the alveoli -> allergic alveolitis
What is hypersensitivity? What is it divided into?
An exaggerated response
Divided into immunological and non-immunological.
Immunological ie. ALLERGY. Further divided into
- IgE-mediated ATOPIC DISEASES: hayfever (allergic rhinitis), eczema, asthma.
- Non IgE mediated allergic diseases (eg. Farmers lung)
Non Immunological divided into:
- Intolerance (eg. food)
- Enzyme deficiency (eg. lactase DH def.)
- Pharmacological (eg. aspirin hypersensitivity)
Define allergy
Allergy is an exaggerated immunological response to a foreign substance (allergen) which is either inhaled, swallowed, injected, or comes in contact with the skin or eye
How/why are IgE antibodies produced?
Produced normally as a response to multicellular organisms.
Th2 cells response with IgG1.
Allergy is a Th2 immunity gone wrong or an uneducated Th2 immunity to something it shouldn’t.
How is an allergy developed?
Come into contact with allergen -> body makes IgE with T lymphocytes with the help of Th2 cells.
IgE will flow around blood, go into tissues and bind to the surface of granulocytes including mast cells and basophils.
Basophils are in periphery, mast cells are in your tissues.
IgE will bind to high affinity receptor on these mast cells and stay down for months or years. It is extremely long lasting.
The next time you encounter that specific allergen -> allergen cross links IgE on the mast cell and the mast cell will degranulate and release histamines – immediate. Histamine responsible of acute symptoms. Also leukotrienes and prostaglandins.
However allergen that came into second time will bind to other things. Will be identified by the same specific Th2 cells that were involved in the beginning. Then you get further production of Th2 cytokines and chemokines that bring about chronic symptoms of allergy.
What are the key interleukins produced by Th2 cells that are involved in allergy? What is their role?
IL-4 -> IgE synthesis
IL-5 -> Eosinophil development
IL-9 -> Mast cell development
IL-13 -> IgE synthesis, airway hypersponsiveness
These are cytokines. Involved in signalling which cell to do what. For IgE synthesis, this is class switch.
What is atopy?
Atopy means out of place
•Atopy is the hereditary predisposition to produce IgE antibodies against common environmental allergens
•The atopic diseases are allergic rhinitis, asthma and atopic eczema
• Allergic tissue reactions (in atopic subjects) are characterised by infiltration of Th2 cells and eosinophils
You can be atopic without being allergic. Allergy is the mechanism that results from atopy.
What is the ‘allergic march’?
Term describing the common progression of atopic diseases from atopic dermatitis to allergic asthma.
This is relevant at population level but not at an individual level.
What is rhino-conjunctivitis?
Aka allergic rhinitis
Upper airways disease
17% of pop
Triggers are many, maily arise april-september.
What is asthma? What changes are observed in the lungs?
Asthma is a disease of the lower airways - bronchi etc. It is a very heterogenous disease. Can be allergic, neutrophilic, exercise-induced, obesity, etc.
In healthy individual, nice ratio lumen:muscle, mucus membrane intact.
In asthmatic lung, enhanced smooth muscle – remodeling. Increased amount of mucus secreting cells.
What is extrinsic allergic alveolitis? Give some examples.
Affects alveoli. 0.1 % of pop. Mechanism: inhaling very small allergens (<5 microns) that penetrate distal airways, end up in blood where they can come into contact with antibodies. Examples: Farmer's lung Hot tub lung
Why is allergy on the increase? (Give the 3 theories)
- 20th century life and the environment: something has been put in or removed
- Environment + genetics
- the hygiene hypothesis
How to treat allergy?
- Allergen Avoidance
- Anti-allergic medication
- Immunotherapy (desensitisation/hyposensitisation)
What are the advantages/disadvantages of allergen-injection immunotherapy?
Advantages
•Effective
•Produces long lasting immunity
Disadvantages
•Occasional severe allergic reaction
•Time consuming
•Standardisation problems
