Host defence in the Lung: Non-immune mechanisms

Question 1

Host defences

Answer 1

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 2

Respiratory epithelium

Answer 2

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 3

Chemical epithelial barriers

Answer 3

Antiproteinases
Anti-fungal peptides
Anti-microbial peptides
Antiviral proteins
Opsins

Question 4

Mucus

Answer 4

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).
Protects the epithelium from foreign material and from fluid loss.
Transported from the lower respiratory tract into the pharynx by air flow and mucociliary clearance.

Question 5

Cough

Answer 5

Expulsive reflex.
Causes -irritants, disease, infection.
Afferent limb - receptors within the sensory distribution of the trigeminal, glossopharyngeal, superior laryngeal and vagus nerves.
Efferent - recurrent laryngeal nerve and spinal nerves.

Question 6

Sneeze

Answer 6

Causes - irritation of nasal mucosa, excess fluid in airway.

Question 7

Plasticity

Answer 7

Following an insult/injury the airway epithelium can in (many cases) effect a complete repair.
This is because it exhibits a level of functional plasticity.