Lecture 12- Mucosal Immunology 1 Flashcards
What is MALT,BALT and GALT?
MALT:The mucosa-associated lymphatic tissue is divided into:
BALT (bronchus-associated lymphatic tissue)
and
GALT (gut -associated lymphatic tissue)
Why is the mucosal immune system imprtant?
- 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
What are the main defence strategies of intestinal muscosa and oropharynx?
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
Describe the lymphoid complexes that are found along the GI tract?
The largest amount of lymphoid tissue is found in the oropharynx (waldeyer’s ring) and the terminal ileum
what is a major factor in maintaining a healthy composition of microorganism in the gut?
Diet is a major factor in maintaining a healthy composition
How does goblet cells improve host’s defence?
Goblet cells produce mucus- physio chemical barrier
what are other special properties of the intestinal epithelial cells for improving hosts defence?
Epithelial cells express TLR
Which TLR is expressed on the basolateral surface and what activates it?
TLR5- invading bacteria
When are the NRL located?
Intracytoplasmic
What are the NRL activated by and how?
Bacterial flagellin once bacteria entr the cytoplasm
What’s the other functions of the surface TLR ligation
-TLR ligation will:
1) cause tightening of epithelial junctions
2)Increase proliferation
3)Epithelial motility
All improve barrier function
what is the purpose of the M cells?
-transport antigens to sub-epithelial lymphoid structure
What is the function of paneth cells?
Paneth cells produce human defensin 5 precursor (HD5) HD6 precursor and trypsin
What is the function of trypsin?
Activation of HD5 and HD6 by proteolytic cleavage
Describe what peyers patches are located ?
-Located in the distal ileum areas of the follicle associated epithelium
Compare the peyers patches in the foetus at 30 weeks compared to at puberty?
Foetal human small intestine contains average of 60 peyers patch before the age of 30 weeks
-At puberty max of 240
what does the peyers patch contain?
- Peyers patch contain germinal centres for B and T cells
- Inductive site for immune response
Describe the features of M cells?
- 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
Describe the three main domains of peyers patches?
- The follicular area
- The interfollicular area
- Follicle-associated epithelium
What does the follicular and the interfollicular areas contain?
Have lymphoid follicles with a germinal centre contains:
- proliferating B cells
- Follicular dendritic cells
- macrophages
What is the follicle surrounded by?
Follicle is surrounded by:
-Corona
-subepithelial dome
:these contain mixed cellsincluding B cells, T cells, macrophages and dendritic cells.
How does Follicular associated epithelium (FAE) differs from normal epithelium?
FAE differd in regards to microvilli regularity and length and presence of infiltrating immune cells
how is peyers patches connected to the blood supply and lymphatic system?
Blood supply- endothelial vessels
-Peyers patch to mesenteric lymph node
How does the naive B cells enter the peyers patch?
-Specialised high endothelial venules
What is the result of B cells entering?
If they recognise the antigen coming in from he M cell at the top of Peyers patch, they get activated and start proliferating
which other cell enter the peyers patch via high endothelial venules and happens to them?
- 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
When does the B cells class switch?
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
what happens to the activated B cells and T cells in the pyeres patch?
Most activated T cells and B cells both leave the peyers patch via the lymphatic drainage and reach their destination via the blood
what is the most special influence of peyers patch on B cells what is required for this to occur?
Peyers patch program B cells to produce IgA- This occurs in the influence of nitric oxide and TGF beta from dendritic cells.
