Mucosal Immunity Basic Science

Question 1

What are the physiological functions of mucosal tissues?

Answer 1

• gas exchange
• food absorption
• sensory activities
• reproduction

Question 2

What is the junction between mucosal cells called?

Answer 2

Tight Junction

Question 3

List the mucosal tissues of the GI system?

Answer 3

• oral cavity
• oesophagus
• stomach
• intestine

Question 4

What are the 3 distinctive anatomical features of the GUT mucosal immune system?

Answer 4

• intimate relationship between mucosal epithelia and lymphoid tissue
• organised lymphoid structures unique to mucosal sites
• specialised antigen uptake mechanissm

Question 5

What are 2 distinctive effector mechanisms of Gut mucosal immune system?

Answer 5

• activated/memory T cell predominate

- “natural” effector/regulatory T cells

Question 6

What are 2 distinctive features of the immunoregulatory environment of the gut mucosal immune system?

Answer 6

• active down regulation of immune response

- inhibitory macrophages and tolerising dendritic cells

Question 7

What are Peyer’s patches?

Answer 7

“essentially the lymph nodes of intestine”

-covered by epithelial layer containing specialised cells called M cells (in dome) which have characteristic membrane ruffles (M=Microvilli)

Question 8

What immune cells are inside Peyer’s Patches?

Answer 8

T cells (with germinal centre) and dendritic cells

Question 9

What do M cells do?

Answer 9

M cells endocytose and phagocytose antigens. antigen is transported across the M cells in vesicles and released and then bound to dendritic cells

Question 10

How do dendritic cells sometimes capture antigen from lumen of gut?

Answer 10

By extending processes across epithelial layer

Question 11

What are the 2 distinct layers of the mucosal immune system and what immune cells do they contain?

Answer 11

• lamina propria: CD4 T cells, dendritic cells, macrophages, mast cells, plasma cells
• epithelial layer: CD8 T cell, dendritic cell

Question 12

What immunoglobulins does the gut produce and approx. how much of each?

Answer 12

• IgA 80%
• IgM 15%
• IgG 5%

Question 13

What immunoglobulins does the body produce and how much of each?

Answer 13

• IgG 80%
• IgM 15%
• IgA 5%

Question 14

How does IgA get to lumen?

Answer 14

IgA bound to receptor (poly-Ig receptor) which are endocytosed by cell and transcytosed across cell and released with secretory component attached

Question 15

What is the function of the secretory component bound to released IgA?

Answer 15

To protect the secretory component from proteolytic enzymes in lumen

Question 16

What are the specialised T cells of the gut and where do they lie?

Answer 16

either in the epithelium or in between epithelial cells

Question 17

What 3 substances inhibit dendritic cell maturation in the presence of commensal bacteria?

Answer 17

PGE2, TSLP, TGF-beta

Question 18

What are the mucosal tissues of the respiratory system?

Answer 18

• trachea

- lungs

Question 19

What parts of the eye are mucosal tissue?

Answer 19

• conjunctiva

- lachrymal gland

Question 20

What gland in the face is mucosal tissue?

Answer 20

salivary gland

Question 21

What parts of the uro-genital system are mucosal tissue?

Answer 21

• kidneys
• uterus
• bladder
• vagina

Question 22

How do T cells enter the Peyer’s Patches and what homing receptors are involved?

Answer 22

They enter from blood vessels directed by CCR7 and L-selectin

Question 23

What causes a T cell to become activated?

Answer 23

When they encounter antigen they become activated by dendritic cells

Question 24

Where do activated T cells go from Peyer’s patch?

Answer 24

They drain via the mesenteric lymph nodes to the thoracic duct and return to the gut via the bloodstream

Question 25

What activated T cells home to the lamina propria and epithelium of the small intestine?

Answer 25

Activated T cells expressing alpha4:beta7 integrin and CCR9

Question 26

What do gut-homing effector T cells bind onto epithelium when in blood vessel and what do the gut eptihelial cells express for these T cells?

Answer 26

• MAdCAM-1

- express cytokines