12.10 Immunology: Normal microbiota 1

Question 1

Where are the majority of the bacteria?

Answer 1

Distal colon

Question 2

Where are anaerobes rare?

Answer 2

Stomach (pH)

Question 3

What are the majority of commensal species?

Answer 3

4 main phyla

firmicutes, bacteroidetes, actinobacteria, proteobacteria

Question 4

What type of commensals are associated with vaginal delivery?

Answer 4

Firmicutes, bifidobacteria

Question 5

What is the composition of the microbiota like within a host?

Answer 5

Stable (influenced), each site has a high level of diversity

Question 6

What happens when mice are fed an iron free diet?

Answer 6

Increase in Bifidobacteria/Clostridia

Decrease in bacteroides

Question 7

What happen in germ free mice? How?

Answer 7

Need higher energy intake

microbiota supply nutrients or alter metabolic machinery

Question 8

What do microbiota have to do with metabolic pathways?

Answer 8

Provide important pathways (site composition varies but pathways are similar)

Question 9

What do microbiota produce?

Answer 9

Short chain fatty acids from undigestible carbohydrates (maintain enterocyte differentiation)

Question 10

Why does colonic fermentation of dietary fibres occur?

Answer 10

Energy for colon and liver, also control of gene expression

Question 11

What is the mucosal immune system? What does it contain?

Answer 11

Part of MALT

Largest collection of lymphoid tissue (SI: 400m2)

Question 12

What does immune activation in the gut lead to?

Answer 12

Protection from pathogens (IgA)

Tolerance to normal microbiota/food antigens

Question 13

Where are isolated lymphoid follicles?

Answer 13

Large and small intestine

collection of T and B cells

Question 14

Where are Peyers patches?

Answer 14

Small intestine

Question 15

What do enterocytes do? Where are they?

Answer 15

Secrete TGF-B, CKs, ChKs and anti-microbial peptides

Top of villus

Question 16

What do Goblet cells do? Where are they?

Answer 16

Secrete mucin, lysozyme, lactoferrin

On villi

Question 17

Where are the effector cells located? (in the villus)

Answer 17

Lamina propria lymphocytes

Question 18

Where are Paneth cells? What do they do?

Answer 18

Bottom of crypts, secrete defensins

Question 19

What cells have critical roles in inducing tolerance?

Answer 19

Enterocytes

IEL (incl. innate LCs)

Question 20

What cells are enterocytes?

Answer 20

Goblet, Paneth cells

Question 21

What are the mechanisms for controlleeed antigen access?

Answer 21

M cells, dendritic cells

Question 22

What does IL-22 do?

What produces it?

Answer 22

Enhances microbial defence, epithelial repair and barrier integrity

NK or IELs

Question 23

What do MAIT cells do?

Answer 23

Respond rapidly to bacterial antigens

mucosal associated invariant T cells

Question 24

Where are M cells? How do they sample lumen?

Answer 24

Over lymphoid aggregates

Lack a thick glycocalyx, don’t secrete mucous for easier access

Question 25

What do the DCs in the mucosa do? (4)

Answer 25

Sample antigen

Induce T-cell differentiation

Bias B cell–>IgA

Induce mucosal adressin (a4B7, homing signal and binds MAdCAM1)