1b// Immunology of the Gut Flashcards
What’s the SA of the GI tract?
200m^2
How would describe the GI tract antigen load?
Massive
What is the state of the GI tract immunology?
State of restrained activation:
- Tolerance vs active immune response
- Dual immunological role
What does the homeostasis of the gut and development of healthy immune system require?
presence of bacterial microbiota
What odes germ free mice mean?
have selected microbiota (not lots of strains)
What site is affected in germ-free mice during an immunological defect of the development of the small intestine? And what is the phenotype in germ-free mice compared with conventionally housed mice?
Peyer’s patches
fewer and less cellular
What site is affected in germ-free mice during an immunological defect of the expression of angiogenin-4? And what is the phenotype in germ-free mice compared with conventionally housed mice?
paneth cells
reduced
What is angiogenin 4?
Mouse angiogenin 4 (Ang4) has previously been described as a Paneth cell-derived antimicrobial peptide important in epithelial host defence in the small intestine
What are the 4 major phyla of bacteria in the gut microbiota?
bacteroidetes, firmicutes, actinobacteria, proteobacteria
and also viruses and fungi
What does the gut microbiota provide to our genetics?
Provide traits we have not had to evolve on our own - Genes in gut flora 100 times our own genome.
Essential nutrients; metabolism of indigestible compounds; defence against colonisation of pathogens
How is. there bacterial growth or decrease in the gut microbiota?
What chemical digestive factors does the stomach produce?
HCl
Pepsin
Gastric lipase
What chemical digestive factors does the liver produce?
bile acids
What chemical digestive factors does the pancreas produce?
trypsin
amylase
carboxypeptidase
What chemical digestive factors does the small intestine produce?
brush border
enzymes
What chemical digestive factors does the colon produce?
no host digestive factors
Rank areas of the GI tract from least to most bacterial content.
stomach
duodenum
jejunum
ileum
colon
What is dysbiosis?
an imbalance between the types of organism present in a person’s natural microflora, especially that of the gut, thought to contribute to a range of conditions of ill health.
altered microbiota composition
What are causes of dysbiosis, leading to disease development? (5)
Infection or inflammation
Diet
Xenobiotics
Hygiene
Genetics
What are xenobiotics?
A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual
e.g., pollutants
What are examples of bacterial metabolites and toxins that are created by dysbiosis? (5)
TMAO
4-EPS
SCFAs
bile acids
AHR ligands
What are disease that are caused by dysbiosis?
What are the physical barriers of the mucosal defense?
anatomical:
- epithelial barrier
- peristalsis
chemical:
- enzymes
- acidic pH
What do commensal bacteria do?
occupy an ecological niche
What are the “immunological” mucosal defenses following an invasion?
MALT (Mucosa Associated Lymphoid Tissue)
GALT (Gut Associated Lymphoid Tissue)
Describe the epithelial barrier.
Mucus layer=> goblet cells
Epithelial monolayer=> Tight junctions
Paneth Cells (small intestine)
- Bases of crypts of Lieberkühn.
- Secrete Antimicrobial peptides (defensins) & lysozyme
What is MALT?
mucosa associated lymphoid tissue
Where is MALT found and in what form?
Found in the submucosa below the epithelium, as lymphoid mass containing lymphoid follicles
the oral cavity is rich in immunological tissue