Immune defence in respiratory Flashcards
What are the 4 types of lung defences in a healthy lung?
Physical
Physiological
Humoral
Cellular
What does humidification do?
Prevents the epithelium from becoming dehydrated
What is the way particles are removed?
The large particles are removed before the carina the particles capable of reaching the deep lung are those which range from 1-5micrometres in size
How are particles expelled from the lungs?
Coughing
Sneezing
Gagging
What is mucus?
A gelatinous substance consisting of water and highly glycosylated proteins (mucins)
The gel is impermeable to water and floats on the sol layer on the epithelial and cilia cells
Contains antimicrobial molecules
Where is the mucus layer produced?
The goblet cells and mucus glands produce mucus as globules which then coalesce to form a more or less continuous layer in the central airways
What is the purpose of mucus in the airways?
To trap bacteria viruses and other particles and either to inactivate them or expel them before they can cause damage to the lungs
How is the mucus expelled?
The cilia beat underneath the gel layer and push the mucus blanket up and out towards the pharynx to be swallowed or coughed up. It takes 30-60 minutes to remove mucus from the large bronchi but can take several days to remove it from the small bronchioles
How can long-term smoking affect mucus removal?
Smoking reduces mucociliary transport causing to an increased risk of recurrent infection and causing longer exposure to the carcinogenic material
What can reduce mucociliary clearance?
Air pollutants
Local and general anesthetic
Smoking
Products of bacterial and viral infection
Examples of congential conditions which decrease mucociliary clearance
‘immotile cilia’ syndrome – absecence of the dynein arms in the cilia
Cystic fibrosis – ciliary dykinesia and abnormally thick mucus
Reduced mucocilary clearance leads to
Recurrent infections and eventually bronchiectasis
What 3 factors influence the composition of the respiratory microbiome?
Microbial immigration – inhalation or microaspiration from GI tract
The local growth conditions – e.g. temp, pH, nutrients etc.
Microbial elimination – by the usual mechanisms e.g. the mucociliary escalator etc.
How do neutrophils react to foreign material?
They migrate out of pulmonary capillaries and phagocytose and kill the microbes
use extracellular traps to ensnare extracellular bacteria
generate mediators activating dendritic cells and B cells
produce the T cell activating cytokine IL-2 enhancing neutrophil-mediated defence during pneumonia
