GALT and Immune System Flashcards
What is the lymphatic system
• Largest immune organ
• Continuous exposure to antigens
• Tolerate food protoins
• Permits commensal (non-pathogenic) bacteria to survive & protects from pathogens / toxins
What are peyer’s patches
Regions of the gut where they must us layer is thin and the antigens are exposed in a controlled way, rich in B and T cells
What are the function of goblet cells
Secrete mucus into the gut
What is the microbiome
The microbes(bacteria, fungi, protozoa and viruses) that reside in the large intestine and their interactions and secretions
What is the microbiota
The organisms themselves/genetic material
What is the function of the microbiota
They are beneficial colonisers that compete against pathogenic bacteria (protective defensive role) and aid the maintenance of the host’s homeostasis via the microbiota-gut-brain axis.
Describe the species in the microbiome
Mainly anaerobes, mostly bacteria, 2 predominant phyla are bacteroidetes and firmicutes
What are the ‘beneficial bacteria’
Lactobacillus, bificobacter
What are the less beneficial bacteria
Staphylococcus, clostridium
Describe the development of the microbiome
Starts from birth via vaginal microbes, Cessation of breastfeeding required for maturation and development of adult-like microbiota
• The microbiome grows and develops with age, and is influenced by external (e.g. diet, lifestyle, medications and stress) and internal (o.g. pH, microbe interactions, temperature, bile acids, immune responses) factors.
Play
What are the functions of the microbiome
The bacteria in the microbiome help to:
• Digest food
• Produce vitamins
• Regulate the immune system (mother i infant)
• Compete against pathogenic bacteria (protection)
• Dysfunction of the microbiome are associated with autoimmune
diseases:
• Accumulation of disease-causing microbes changes gene activity and metabolic processes i abnormal immune response against host antigens
• Diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis
and fibromyalagia
Describe the barrier effect of the microbiome in immune function
Competitive exclusion / Barrier effect: prevents colonisation by pathogenic
microbes.
- Many intestinal bacteria produce antimicrobial compounds (bacteriocins)
-Competition for nutrients (due to larger cell population)
-Competition for host cell attachment sites on epithelial cells (prevents entry
of pathogens across epithelial layer).
Describe how the microbiome is involved in signalling to the innate immune system
Signalling to innate immune system (GALT):
- Protective response to commensal bacteria
- Inflammatory response to pathogenic microorganisms
- Trigger phagocytosis of an infected cell
- Prevention of allergies
What is the gut-brain axis
Communication system integrating neural,
hormonal and immunological signalling between
the gut and brain
• Bi-directional
• Influenced by stress
Describe the functions of the gut-brain axis
-Alters composition of gut microbiota
-Alters host’s stress reactivity (over-reaction)
-Alters integrity of gut epithelium
-Alters peristalsis, secretions and mucin production
Describe how the microbiome is involved in energy homeostasis
Microbial metabolites include short chain fatty
acids (SCFA), bile acids and neuroactives (GABA,
histamine, acetylcholine, dopamine, serotonin) -Microbial metabolites may influence host gene
expression, affect the enteric nervous system, alter
bile acid signalling and central appetite pathways
Describe how the gut microbiome is linked to IBS
Variation in gut microbiota contributes to low-grade
intestinal inflammation
2-fold increase ratio Firmicutes:Bacteroidetes
Disturbed colonic fermentation
Adhesion of enteric pathogens to epithelial cells
Describe how the gut microbiome is linked to inflammatory bowel disease
Crohn’s disease and ulcerative colitis
Loss or overabundance of microbial species results in persistent inflammatory response
Reduced abundance and diversity of Firmicutes (reduced synthesis SCFA with potent anti-inflammatory properties)
Describe how the microbiome is linked to obesity
Studies in twins show that obese individuals have less biodiverse microbiome, higher level of enzymes so they are more efficient at digesting food and harvesting calories.
Possibly linked to increased ratio of Firmicutes:Bacteroidetes
Higher excretion of SCFA in obese individuals
Microbiota contributes to non-alcoholic fatty liver disease steatohepatitis
Bariatic and gastric by-pass surgery alters the gut
microbiota composition
What are probiotics
live microorganisms which when administered in
adequate amounts confer a health benefit on the host
What are prebiotics
stimulate the growth of probiotics (but if there is no
such thing as a probiotic….?
What are symbiotics
combination of pre and probiotics. No evidence of
synergy actually needed
What are postbiotics
dead bacteria, but which still have an effect?
Why are probiotics limited
Level of evidence needed for a substantiated claim.
Is it possible to trial a “probiotic”?
Read manufacturers claims very carefully
Dose, mixed or single species
