Host defence in the lung 2

Question 1

non-respiratory lung functions

Answer 1

• Synthesis, activation and inactivation of vasoactive substances, hormones, neuropeptides
• Lung defence: complement activation, leucocyte recruitment, host defence proteins, cytokines and growth factors
• Speech, vomiting, defecation.

Question 2

host defences

Answer 2

• Intrinsic: Always present: Physical and chemical. Apoptosis, autophagy, RNA silencing, antiviral proteins
• Innate defence: Induced by infection (Interferon, cytokines, macrophages, NK cells
• Adaptive immunity: Tailored to a pathogen (T cell, B cells)

Question 3

respiratory epithelium

Answer 3

serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.

Question 4

chemical epithelial barriers

Answer 4

•	antiproteinases 
•	anti-fungal peptides
•	anti-microbial peptides
•	Antiviral proteins 
•	Opsins 
Produced by most (all?) epithelial cells

Question 5

endogenous commensal

Answer 5

non-specific defence mechanism, bacterial flora

Question 6

mucus

Answer 6

• Airway mucus is a viscoelastic gel containing water, carbohydrates, proteins, and lipids.
• It is the secretory product of the mucous cells (the goblet cells of the airway surface epithelium and the submucosal glands).
• Mucus protects the epithelium from foreign material and from fluid loss
• Mucus is transported from the lower respiratory tract into the pharynx by air flow and mucociliary clearance.
• Mucus clearance via the escalator – cilia beat in directional waves to move the mucus up the airways

Question 7

coughing

Answer 7

non-immune defence mechanism

expulsive reflex that protects the lungs and respiratory passages from foreign bodies

Question 8

sneeze

Answer 8

the involuntary expulsion of air containing irritants from nose
causes: irritation of nasal mucosa, excess fluid in airway

Question 9

consequences of damage to epithelial cells

Answer 9

Plasticity exists in multiple cells – good thing
If the process goes wrong we get pulmonary disease – bad thing
• Mucus plugs/inflammation is associated with severe disease
• Mucus and inflammatory cells blocking the airways. Hence the term obstructive lung is sometimes used
• Mucus plugs can completely obstruct the airways and can be fatal