Microbiota Flashcards
What are the 2 major tools for analyzing microbiota-immune system relationships?
- High throughput DNA sequences (can visualize microbiome)
2. Germ-free animals
What are some of the contributions of gut bacteria to good immune health?
- provide energy for metabolizing dietary polysaccharides
- provide vitamins
- required for development of immune system
- protect from disease caused by pathogenic bacteria
How do commensal bacteria protect from intestinal inflammation?
by balancing pro- and anti-inflammatory immune reactions (some bacteria promote inflammatory helper T-cells, while others promote Treg cells)
Which bacteria can be used to protect against harmful effects of IBD / treat it?
bacteroides fragilis (induces Tregs)
What are non-GI diseases that result from altered gut microbiota?
allergy, autoimmunity (MS, EAE), metabolic syndrome (obesity)
What is IBD likely a result of?
- *commensal bacteria=initiating factor
- changes in development or composition of intestinal microbiota (dysbiosis)
- T-cell mediated inflamm. response due to stim. by microbial agents
When did the increase in prevalence of asthma/allergy, eczema, and hay fever really start skyrocketing? Why?
in 1990 due to hygiene hypothesis (lower incidence of infection in early childhood leads to increased susceptibility of certain diseases, particularly allergies and autoimmune disorders)
Absence of microbes leads to increased serum levels of which antibody?
IgE
Interestingly, a _______ in infectious diseases results in a _____ in immune disorders.
decline; rise
What is needed to prevent an increase in IgE antibodies?
exposure to microbiota early in life (as demonstrated by mice experiments in which pathogen-free mice have low levels of serum IgE if they are exposed to microbiota before first 35 days of life; exposure beyond 12 weeks=significant increase in serum IgE)
In addition to early exposure to microbiota, also need ______ microbiota to prevent an increase in IgE.
diverse
Why is “weaning” considered an important time for the infant?
A lot of immune activity happens when a baby is being weaned off breast milk, including generation of Tregs. Antibiotics can disrupt the weaning reaction and cause high susceptibility to pathological inflammation (known as “pathological imprinting”).
Which diseases can result from disruption of the weaning reaction?
colitis, allergic inflammation, cancer
What is the implication of insufficient Th1 response due to decreased bacteria and viral infections?
increased Th2 response (IgE)
Can intestinal microbiota actually cause metabolic syndrome, like obesity?
Yes, as demonstrated by TLR5-/- mice (ligand for TLR5=bacterial flagella). Fecal transplant from obese TLR5 KO mice to antibiotic-treated WT resulted in obese mice.
