lung immunology

Question 1

examples of airway respiratory diseases

Answer 1

Allergic airway diseases:
Upper airways: allergic rhinitis
Bronchi: asthma
Alveoli: allergic alveolitis

Question 2

define hypersensitivity

Answer 2

Hypersensitivity: exaggerated response, divided to immunological (allergy) and non-immunological reactions

Question 3

difference between immunological and non-immunological

Answer 3

Immunological: can be IgE-mediated (atopic diseases e.g. Hayfever, eczema and asthma) and non-IgE-mediated (allergic e.g. Farmer’s lung)
Non-immunological: can be intolerance, enzyme deficiency, or pharmalogical (e.g. Aspirin hypersensitivity)

Question 4

what is allergy?

Answer 4

exaggerated immunological response to a foreign substance (allergen) which is either inhaled, swallowed, injected, or comes in contact with the skin or eye; MECHANISM not a disease

Question 5

Asthmatic airways: have a lot of ?

Answer 5

Asthmatic airways: have a lot of IL4/5 and eosinophils

Question 6

Pathophysiology of seasonal allergic rhinitis:

Answer 6

Infiltration of allergens through nasal mucosa
Dendritic cells capture allergens and travel to lymph nodes
B-cells differentiate to IgE producing plasma cells
IgE priming of mast cells

Question 7

Atopy is?

Answer 7

hereditary predisposition to produce IgE antibodies to common allergens; atopic diseases = allergic rhinitis, asthma and atopic eczema; allergic tissue reactions are characterised by infiltration of TH2 cells and eosinophils

Question 8

what is the allergic march?

Answer 8

it describes the common progression of atopic diseases from atopic dermatitis to allergic asthma

eg food allergies from birth but need chronic (several seasons) exposure to develop allergic rhinitis

Question 9

describe Rhino-conjunctivitis

Answer 9

summer hay fever

seasonal/perennial affecting up to 25% of the population; seasonal form affects 10-12% children

Question 10

Common causes of perennial allergic rhinitis

Answer 10

Common causes of perennial allergic rhinitis: house dust mites, cats, dogs, alternaria, cockroaches and horses

Question 11

Asthma- what does it’s phenotype depend on?

Answer 11

Asthma: affects 8-12% population; very heterogeneous, with phenotypes based on control and severity or endotypes (neutrophilic/allergic/eosinophilic/exercise induced)

Question 12

mechanisms on extrinsic alveolitis

Answer 12

Exposure to small allergenic particles that penetrate distal airways (less that 5 microns), captured by antibodies in the interstitium (on pulmonary capillary) causing immunological cascades, complement and neutrophils/macrophages

Question 13

the principles of treatment of allergic diseases

Answer 13

Principles of treating allergic disease: allergen avoidance, anti-allergic medication (antihistamine then intra-nasal steroids) and immunotherapy (desen/hyposensitisation)

Seasonal allergic rhinitis: runny nose, sneezing, congestion, leading to decreased productivity

Allergen immunotherapy: either subcutaneously or daily sublingually to gradually expose to and then desensitise them to allergens; effective and long-lasting although risk of severe reaction, time consuming and standardisation problems

Question 14

allergen can be either?

Answer 14

subcutaneous or sublingual

Question 15

pros and cons of allergen-injection immunotheraphy (hyposensitisation/ desensitisation)

Answer 15

advantages:
effective, produces long lasting immunity

disadvantages:
occasional severe allergic reaction, time consuming, standardisation problems

Question 16

mechanism on allergic rhinitis

Answer 16

Allergic rhinitis:
Allergens pass over epithelium in the airways and are captured by dendritic cells
Dendritic cells migrate to lymph nodes and stimulate TH cells to differentiate to TfH (using IL4) and TH2 cells (using IL9) that activate B-cells and mast cells respectively
TfH cells stimulate B-cells to become plasma cells that secrete allergen specific IgE antibodies that bind to FcE receptors on mast cells
When the allergen cross links IgE antibodies on mast cells, degranulation occurs leading to histamine release

Question 17

mechanism on extrinsic allergic alveolitis

Answer 17

Extrinsic allergic alveolitis:
Small allergenic particles penetrate distal airways ant enter alveoli, then interstitium
Particles are captured by antibodies in the interstitium to form antigen-antibody complexes
Complement and immunological cascades are triggered and lymphocytes are recruited

Question 18

Immunotherapy mechanism:

Answer 18

subcutaneous/sublingual exposure to traces of the allergen leads to desensitisation because TH cells become Tregs that inhibit TfH cells, stopping the producting of IgE antibodies; they can also cause B-cells to become Bregs that inhibit B-cells or become plasma cells that produce IgG/A antibodies that compete for allergen binding with IgE, reducing the hypersensitivity response