Barriers Flashcards
Which immune system are barriers a part of?
Innate
Where are the vast majority of the body’s immune resources directed towards?
Barriers
Epithelial tight junctions
Specific cell adhesion
There are many layers to the epithelium. Each layer has a function. What are three?
Shedding
Tight junctions
Lipid layer
Cilia
What are they? Where are they? What do they do?
Active, hair-like structures
The apical surface of airway epithelium
Sweep and propel mucus
What can lead to the dysfunction of Cilila?
Smoking
Smokers cough
What does Cilia not work without?
MUCUS
Does the GI tract have cilia?
NO
Just mucus
Sheds/sloughs
What is mucus comprised of?
Glycoprotein and water
A mucus dysfunction leads to what illness?
Cystic Fibrosis
What is Cystic Fibrosis?
A mutation in a chloride pump that cannot regulate
Makes mucus think - no air exchange
What three things does the barrier system reinforce with?
Chemicals (acid)
Enzymes (lysosome)
Molecular (defensins, IgA)
4 chemical mechanisms that help barrier
Stomach acid - pH 2 - ACID
Skin - slightly acidic, glands secrete lipids
Salts in sweat make it hypertonic
Intestine - pH above 7 - ALKALINE
The enzymatic molecule that helps with barrier
Lysozyme
Where can you find lysozyme?
Tears, saliva, milk, GI mucus
What does lysozyme do?
Catalyzes the breakdown of peptidoglycan in bacterial cell walls
Does lysozyme need to be specific?
No, we don’t have a sugar base cell wall
What 3 molecular defenses coat barrier surfaces?
a-defensin
b-defensin
antibodies (IgA)
What are defensins?
tiny - 30 aa peptides
How do we produce defensins and in what form?
Produced by epithelial cells, paneth cells, and neutrophils
In an inactive form
What can upregulate defensins?
cytokines
two ways the defensin direct antimicrobial activity?
Disrupt membranes
Impair DNA/RNA synthesis
How are defensins activated?
proteolytically cleaved
What does defensin activate?
Leukocytes
a-defensins
Where?
How are they produced and released? 2 ways
What do they do?
found in mucosal secretions
paneth cells –> gut mucosa
neutrophils –> stored in granules
Direct anti-microbial activity
b-defensin
Produced?
Stored?
What do they do?
Skin epithelial cells
stored in lipid-rich lamellar bodies
Lamellar bodies produce a water-proof barrier on the skin
What is a dedicated molecule to remove IgA?
Immunoglobulin
Normal flora
What? Where?
Non-pathogenic commensal bacteria
Most barriers are coated
How does the Normal flora help with immunity? 3 things
Occupy space - preventing attachment
Stimulate defensin and IgA
Maintain immune tolerance
