Lecture 12- Mucosal Immunology 1

Question 1

What is MALT,BALT and GALT?

Answer 1

MALT:The mucosa-associated lymphatic tissue is divided into:
BALT (bronchus-associated lymphatic tissue)
and
GALT (gut -associated lymphatic tissue)

Question 2

Why is the mucosal immune system imprtant?

Answer 2

• Biggest immune compartment of the organism
• Harbours 60% of all effector cells
• Direct contact with the outside environment
• continuous antigen stimulation- food, endogenous flora and pathogens
• muscosal sites are entry for many infections

Question 3

What are the main defence strategies of intestinal muscosa and oropharynx?

Answer 3

1) Endogenous flora
2) Epithelium and mucus:
- Mechanical barriers (cells and tight junctions)
- mucins: extensively glycosylated proteins from a viscous barrier
- specialised epithelial cells (goblet cells, M cells, paneth cell)
- Antimicrobial substances (defensins, lysozymes, lactoferrins and phospholipases)
3) Regionalised immune systems and gut homing of B and T cells
- Waldeyer’s ring ( lingual and palatine tonsils, nasopharyngeal tonsils)
- Peyers patch
- Mesenteric lymph nodes
- Intraepithelial immune cells
- Lamina propria immune cells including sampling DC

Question 4

Describe the lymphoid complexes that are found along the GI tract?

Answer 4

The largest amount of lymphoid tissue is found in the oropharynx (waldeyer’s ring) and the terminal ileum

Question 5

what is a major factor in maintaining a healthy composition of microorganism in the gut?

Answer 5

Diet is a major factor in maintaining a healthy composition

Question 6

How does goblet cells improve host’s defence?

Answer 6

Goblet cells produce mucus- physio chemical barrier

Question 7

what are other special properties of the intestinal epithelial cells for improving hosts defence?

Answer 7

Epithelial cells express TLR

Question 8

Which TLR is expressed on the basolateral surface and what activates it?

Answer 8

TLR5- invading bacteria

Question 9

When are the NRL located?

Answer 9

Intracytoplasmic

Question 10

What are the NRL activated by and how?

Answer 10

Bacterial flagellin once bacteria entr the cytoplasm

Question 11

What’s the other functions of the surface TLR ligation

Answer 11

-TLR ligation will:
1) cause tightening of epithelial junctions
2)Increase proliferation
3)Epithelial motility
All improve barrier function

Question 12

what is the purpose of the M cells?

Answer 12

-transport antigens to sub-epithelial lymphoid structure

Question 13

What is the function of paneth cells?

Answer 13

Paneth cells produce human defensin 5 precursor (HD5) HD6 precursor and trypsin

Question 14

What is the function of trypsin?

Answer 14

Activation of HD5 and HD6 by proteolytic cleavage

Question 15

Describe what peyers patches are located ?

Answer 15

-Located in the distal ileum areas of the follicle associated epithelium

Question 16

Compare the peyers patches in the foetus at 30 weeks compared to at puberty?

Answer 16

Foetal human small intestine contains average of 60 peyers patch before the age of 30 weeks
-At puberty max of 240

Question 17

what does the peyers patch contain?

Answer 17

• Peyers patch contain germinal centres for B and T cells

- Inductive site for immune response

Question 18

Describe the features of M cells?

Answer 18

• Small microvilli
• Large cell membrane fenestration: these features enhance antigen uptake from the gut lumen
• Trans-cellular transport of antigen
• Exocytosis at basolateral membrane
• Delivery of dendritic cells in some region of underlying lymphatic structure

Question 19

Describe the three main domains of peyers patches?

Answer 19

• The follicular area
• The interfollicular area
• Follicle-associated epithelium

Question 20

What does the follicular and the interfollicular areas contain?

Answer 20

Have lymphoid follicles with a germinal centre contains:

• proliferating B cells
• Follicular dendritic cells
• macrophages

Question 21

What is the follicle surrounded by?

Answer 21

Follicle is surrounded by:
-Corona
-subepithelial dome
:these contain mixed cellsincluding B cells, T cells, macrophages and dendritic cells.

Question 22

How does Follicular associated epithelium (FAE) differs from normal epithelium?

Answer 22

FAE differd in regards to microvilli regularity and length and presence of infiltrating immune cells

Question 23

how is peyers patches connected to the blood supply and lymphatic system?

Answer 23

Blood supply- endothelial vessels

-Peyers patch to mesenteric lymph node

Question 24

How does the naive B cells enter the peyers patch?

Answer 24

-Specialised high endothelial venules

Question 25

What is the result of B cells entering?

Answer 25

If they recognise the antigen coming in from he M cell at the top of Peyers patch, they get activated and start proliferating

Question 26

which other cell enter the peyers patch via high endothelial venules and happens to them?

Answer 26

• Naive CD4 Tcells also enter peyers patch via the high endothelial venules
• If they encounter a dendritic cell presenting antigen to them that they recognise
• They proliferate and increase in number
• Some of CD4 cells may then encounter B cells activated by the same antigen

Question 27

When does the B cells class switch?

Answer 27

When T cell/B cell help takes place: they activate each other, T cells move onto to become mature cells and B cells under Immunoglobulin class switch into plasma cells

Question 28

what happens to the activated B cells and T cells in the pyeres patch?

Answer 28

Most activated T cells and B cells both leave the peyers patch via the lymphatic drainage and reach their destination via the blood

Question 29

what is the most special influence of peyers patch on B cells what is required for this to occur?

Answer 29

Peyers patch program B cells to produce IgA- This occurs in the influence of nitric oxide and TGF beta from dendritic cells.