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metabolism > gut as an immune organ > Flashcards

gut as an immune organ Flashcards

1
Q

what is the surface area of the skin?

A

25m2

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2
Q

what is the surface area of the mucosae?

A

32m2

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3
Q

why does the mucosae have such a large surface area?

A

due to its length and the presence of villi and microvilli

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4
Q

what lines the gut and what is its function?

A

a layer of epithelium

selective barrier of absorption

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5
Q

name organisms which cause infections of the gut or which enter the body through the gut

A 
Vibrio cholera
Helicobacter pylori
Salmonella enteritidis
Giardia lamblia
Clostridium difficile
Worms
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6
Q

what immune cells are normally found in the small intestine?

A

T cells

IgA plasma cells

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7
Q

what are the two T cell markers?

A

CD4 and CD8

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8
Q

what is cluster of differentiation?

A

an immunohistochemistry technique used to identify and investigate cell surface molecules in T cells

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9
Q

what does the CD4/CD8 ratio show and what should it normally be?

A

immune system health

between 1 and 4

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10
Q

what are Peyer’s patches?

A

organised lymphoid follicles

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11
Q

where are Peyer’s patches found?

A

small intestine

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12
Q

what cells are Peyer’s patches rich in?

A

T cells

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13
Q

what are M cells?

A

specialised epithelial cells of the GALT and MALT which sit on top of PPs

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14
Q

what do M cells do?

A

sample the antigens of the gut lumen

transport antigens from lumen across the epithelium to APCs

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15
Q

what are the main type of APCs in the gut?

A

dendritic cells

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16
Q

how can dendritic cells sample the gut content?

A

directly

via the peyer’s patch

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17
Q

which vitamin is retinol?

A

vitamin A

18
Q

which enzyme is needed to convert retinol to retinoic acid?

A

retinal dehydrogenase from gut dendritic cells

19
Q

explain how b and T cells gain gut homing capacity

A

retinoic acid binds to T cell DNA

activates transcription of CCR9 and a4b7

20
Q

what are enterocytes?

A

intestinal epithelial cells

21
Q

how do gut homing cells know to home to the gut mucosa?

A

only enterocytes express CCL25 and MadCAM - ligands interact with gut homing T cell receptors to stop them from circulating

22
Q

what is the ligand for the CCR9 receptor and what type of molecule is it?

A

CCL25

chemokine

23
Q

what is a chemokine?

A

a molecule which makes cells move

24
Q

what is the ligand for the a4b7 receptor?

A

MadCAM

25
Q

what is the main immunoglobulin in lymphoid organs?

A

IgG

26
Q

what are the main immunoglobulins in the mucosa?

A

IgM and IgA

27
Q

how many amino acids in the constant region of IgA and IgM?

A

18

28
Q

why is a cysteine residue needed in IgM and IgA?

A

polymerisation

29
Q

what do J chains do?

A

act as the glue between two Fc regions in an antibody

30
Q

what shape is IgA in mucous secretions?

A

dimer

31
Q

what shape is IgA in the plasma?

A

monomer

32
Q

what shape is IgM in mucous secretions?

A

pentamer

33
Q

what shape is IgM in the plasma?

A

pentamer

34
Q

how is IgA actively transported across the epithelium into the gut lumen?

A

polymeric Ig receptor

35
Q

what does SIgA protect against?

A

enteric toxins and pathogenic microorganisms

36
Q

through what methods does SIgA clear antigens and pathogens from the intestinal lumen?

A

blocking access to epithelial receptors
trapping them in mucus
facilitating their removal by peristaltic and mucociliary activities

37
Q

which immunoglobulin can you live without?

A

IgA

38
Q

what percentage of people with coeliac disease have IgA deficiency?

A

2%

39
Q

summarise how the immune system deals with viruses and bacteria in the gut

A
  1. The gut immune system has to know what antigens are in the gut
  2. Peyer’s patch M cells sample antigen
  3. T and B cells activated in PP migrate to the mucosa
  4. IgA is actively transported across the epithelium by the polyIg receptor
  5. In the lumen IgA agglutinates viruses and bacteria
40
Q

what ligand do the breast epithelium and endothelium express?

A

endothelium - MadCAM

epithelium - CCL25

41
Q

which immunoglobulin are babies totally deficient in?

A

IgA

42
Q

wha is coeliac disease?

A

an autoimmune disease of the small intestine

metabolism (23 decks)

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