Microbiota and the immune response

Question 1

what percentage of the cells in our body are microbial?

Answer 1

90%

Question 2

where is most bacteria located

Answer 2

the large intestine

Question 3

what can change the microbiome

Answer 3

stress, diet, antibiotics- imbalances can lead to inflammatory bowel disease, allergy and autoimmunity

Question 4

benefits of microbials

Answer 4

required for development of the immune system, provide energy by metabolizing dietary polysaccharides, provide vitamins, protect from pathogenic bateria

Question 5

commensal bacteria are

Answer 5

present at all mucosal surfaces and the composition is different at each site

Question 6

germ free animals immune systems

Answer 6

have almost no secondary lymphoid tissues including mucosal tissues

Question 7

Clostridium difficile

Answer 7

disease that occurs after treatment with antibiotics that kill the commensal bacteria in the gut

Question 8

proof of probiotics protective effects

Answer 8

mice given an oral does of a commensal bacteria (Bacillus subtilis) were protected from E. coli.

Question 9

How Can Commensals Protect from Intestinal Inflammation?

Answer 9

Balance pro and anti-inflammatory immune responses. Some bacteria promote TH cells; others promote Treg cells

Question 10

Dysbiosis favors

Answer 10

pro-inflammatory (TH17 and TH1) over anti-inflammatory (Treg) state

Question 11

Inflammatory Bowel Disease (IBD)

(Crohn’s disease and ulcerative colitis)

Answer 11

T cell-mediated inflammatory response due
to stimulation by microbial antigens

IBD likely due to changes in development or
composition of intestinal microbiota (dysbiosis)

Commensal bacteria thought to be initiating factor

can be transferred via fecal transplant

Question 12

allergy is decreased in

Answer 12

Children growing up on farms

Children attending day care during 1st 6 months of life

East German children compared to children in more
developed West Germany

Question 13

Allergy is increased in

Answer 13

children given antibiotics in the first year of life

Question 14

Hygiene hypothesis

Answer 14

early childhood infections lead to protection from allergy later in life. early life exposure to some microbes can alter susceptibility to disease particularly allergy

Question 15

what happens to antibiotic treated mice vs. normal mice exposed to dust mites

Answer 15

Antibiotic treated mice were more likely to develop allergies to dust mites

Question 16

Balance Between TH1 and TH2 Cells

Answer 16

Bacteria and viruses elicit TH1 responses
(IL-2 and INFγ)
TH1 responses down regulate TH2 response
which produces IgE (allergy)
Insufficient TH1 response due to decreased
bacteria and viral infections would increase
TH2 response (IgE)

Question 17

Autoimmunity and comensal bateria

Answer 17

intestinal bacteria were shown to protect mice from autoimmune disease by inducing anti-inflammatory Treg cells

Question 18

TLR5-/- mice:

Answer 18

Have increased food intake, insulin resistance,
hypertension and are obese (metabolic syndrome)
Have altered gut microbiota (dysbiosis)
Antibiotic treatment reversed obesity
Fecal transplant of obese TLR5-/- mice into antibiotic treated normal mice caused obesity- suggests that microbiota can cause obesity

Question 19

how does a high fat diet change microbiota

Answer 19

affects intestinal lymphoid cells to secrete IL-22 which induces expression of anti-microbial peptides altering microbiota and promoting obesity

Question 20

Causes of Dysbiosis

Answer 20

• antibiotics
• Diet (especially high fat)/stress
• early childhood experiences- hygiene hypothesis
• Cesarean delivery
• genetics

Question 21

C-section deliveries promote microbiota more similar to

Answer 21

mothers skin microbiota

Question 22

gut microbiota affects on cancer therapy

Answer 22

when microbiota are decreased by antibiotics cancer therapy is not as affective