Lung immunology

Question 1

Allergy

Answer 1

exaggerated immunological response to a foreign substance (allergen) which is either inhaled, swallowed, injected, or comes in contact with the skin or eye.

Allergy is a mechanism (not a disease).

Question 2

Intolerance

Answer 2

– inability to consume or absorb/metabolise

nutrients.

Question 3

Atopy

Answer 3

hereditary predisposition to produce IgE
antibodies against common environmental allergens
(the genetic tendency to develop allergic diseases.)

Question 4

Hypersensitivity

Answer 4

– exaggerated response.

Question 5

Atopic allergic reactions are characterised by

Answer 5

infiltration of Th2 cells and eosinophils

e.g. allergic rhinitis+ asthma

Question 6

Atopic diseases

Answer 6

o Allergic rhinitis.
o Asthma.
o Atopic eczema

Question 7

Upper airway disease example

Answer 7

Hay fever
▪ Allergic Rhino-conjunctivitis (seasonal and perennial) affects up to 17% of the population → THIS IS HAYFEVER.
▪ Allergens vary from grass pollens, tree pollens, weed pollens and fungal pollens (the levels of which vary from season to season).
▪ Common causes of hay fever and asthma include:
o House dust mite.
o Cats and dogs.
o Alternaria (a form of fungus).
o Cockroaches.
o Horses.

Question 8

Example of middle/ lower airways disease

Answer 8

Asthma
▪ Asthma is a very heterogeneous disease (many phenotypes):
o Intermittent, mild, allergy frequently
o Persistent, manageable, allergy
o Chronic/severe, infection (not allergy)
▪ Symptoms of asthma include cough, dyspnoea, wheezing, chest tightness and secretions (due to bronchoconstriction).

Question 9

Example of middle/ lower airways disease

Answer 9

Anaphylaxis
General symptoms:
Dizziness, seizures, loss of consiousness, anxiety, lip/ tongue swelling, laryngeal oedema, bronchoconstriction, tingling, vomiting, diarrhoea

▪ Causes include:
o Drugs (e.g. penicillin).
o Foods (e.g. nuts, milk, eggs fish etc.).
o Insect stings and latex.
▪ Relief though epinephrine injections.
▪ There is an overlap of atopic diseases such as hay fever AND asthma.

Question 10

Example of lower/ distal airways disease

Mechanism

Answer 10

Extrinsic Allergic Alveolitis
▪ EAA affects 0.1% of the population.
▪ Examples include:
o Farmer’s Lung → mouldy hay.
o Bird Fancier’s Lung → bird droppings.
o Air conditioner Lung → air conditioner moulds.

Mechanism:
1. Small allergen particles enter the alveolus and pass
into the interstitium.
2. Allergic responses occur when antibodies bind to the
allergens and stimulate a DTH (delayed- type hypersensitivity) response.

Question 11

Pattern of allergic airway disease

Answer 11

gradual decrease in infectious disease while there has been an INCREASE in allergic and autoimmune diseases

Question 12

How many diagnosed with asthma?

Answer 12

5.7m people

Question 13

increase in hospital admissions due to anaphylactic shock from 1990 → 2000?

Answer 13

7x increase in hospital admissions due to anaphylactic shock from 1990 → 2000.

Question 14

Rising trends of ?

Possible causes? (microbial+ non-microbial)

Answer 14

Allergy

▪ Factors could be microbial:
o Water sanitation (less oro-faecal infections).
o Food quality (lack of fermenting bacteria).
o Poverty (high asthma rates in urban).
o Medical intervention.
▪ Factors could be non-microbial:
o Pollution (air, water, food).
o Diet and nutrition (lack of Vit-D, fish oil etc.).
o Obesity.
o Stress.
o Bad genes.

Question 15

Principles of Treatment of allergic airway disease

Answer 15

o Allergen avoidance.
o Anti-allergic medication.
o Immunotherapy – desensitisation/hyposensitisation: Allergen-injection Immunotherapy.

Question 16

Allergen-injection Immunotherapy advantages+ disadvantages

Answer 16

Advantages – effective, produces long lasting immunity.

Disadvantages – occasional anaphylaxis, time consuming, standardisation problems.

▪ SCIT – Specific immunotherapy by sub-Cutaneous Injection involves injections of increasing doses of allergen over a long period of time to
desensitise – could shift Th2 to Th1 profiles.

Question 17

Allergen-injection Immunotherapy process

Answer 17

▪ Over a long period of time, levels of Th2 drop
while levels of Th1 and TReg cells increase.
▪ This changes the profile of cytokines which
reduces the allergic response.