Mucosal Immunology Flashcards
What are the 3 main structures of the gut epithelial barrier?
Crypt
Vili
Peyer’s patch
What is the function of the crypt?
Found at the bottom of the vili
They contain many Lgr5+ stem cells at their base which proliferate and differentiate as they move up the crypt, to replace shedding cells at the tip
Where are immune cells found in the mucosa?
In the lamina propria
What is tolerance?
The ability of the gut mucosal immune cells to detect and differentiate between gut microbiota and pathogens
How do commensal microbes impact the intestinal epithelial cells?
PRRs on epithelial cells respond to microbes
This stimulates cytokine and AMP production
The cells can then release mucins which act as energy sources for microbes
What is an example of a microbial metabolite?
Tryptophan catabolites
SCFA - Short Chain Fatty Acids
How do tryptophan catabolites impact the intestinal epithelial cells?
They stimulate anti-inflammatory substances and protection in repair
How do Short-Chain Fatty Acids impact the intestinal epithelial cells?
They act as an energy source and regulate permeability
How do bacterial metabolites impact the epithelium?
Thy stimulate serotonin production, stimulating the enteric nervous system and inflammation
Where are M cells found?
In the epithelium of the Peyer’s patches
What is the function of an M cell?
They take up antigens by endocytosis and phagocytosis, releasing the antigens at the basal surface
What is the function of dendritic cells in gut mucosal immunology?
They bind to antigens that are released by M-cells in the Peyer’s patch
They can also extend through the epithelial layer to capture antigens from the gut lumen
They can then activate T-cells with the bound antigens on MHC, using co-stimulatory molecules ((Den)CD80/86—(T)CD28) and IL-12 production
How do Gut homing T cells enter the lamina propria?
They express the α4ß7 integral on their surface
This binds to the MAdCAM-1 adhesion molecule on the blood vessel wall allowing for transendothelial migration
How do Gut homing T cells bind to the epithelial cells of the gut?
The epithelial cells express chemokines specific for gut homing T cells
T cells express αEß7 molecules
These bind to E-cadherin on the epithelial
What are intraepithelial lymphocytes?
Lymphocytes that anchor to the gut epithelium
They are mostly CD8+ T cells, fully equipped with killing machinery
