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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

what enlarges the surface area of the mucosa

A

in the small intestine

  • enlarged 1.6 times by place circularise
  • enlarged 60-120 times by vili and microvilli

in the large intestine
- enlarged 6.5 times by the microvilli in the colon

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4
Q

the gut is lined by a…

A

single layer of epithelium, that is 30um across

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5
Q

what is giardiasis lambila

A
  • bacteria that infect the gut
  • they are a Flagellated parasitic microorganism
    = they break the interface and prevent absorption leading to malabsorption
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6
Q

what are the two types of worms

A

Hook worms and tape worms

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7
Q

what do worms do

A
  • they enjoy warm environment and reproduce

- they can create damage as they hook onto the gut and this creates wounding allowing bacteria to infect the gut

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8
Q

what is immunohistochemsitry

A
  • this is using immunology as a way of staining cells
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9
Q

what is the CD4/CD8 ratio a reflection of

A
  • immune system health

- normal ratio is between 1 and 4

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10
Q

what is peyer’s patch

A
  • Organised lymphoid follicles found in the small intestine
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11
Q

How many Peyer’s patch is there

A

there is about 100 of them in the human GI tract

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12
Q

what type of lymphocyte is in Peyer’s patch

A

T lymphocyte – clustered everywhere in the gut, specifically here

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13
Q

what are all the types of cells in the Peyer’s patch

A

M cells
T lymphocytes
Dendritic cells

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14
Q

what do M cells do

A
  • they transport gut antigens across the epithelium into the body
  • they take bacteria from the gut
  • allow antigen presenting cells (APC) to access the gut content
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15
Q

what do dendritic cells do within in Peyer’s patch

A
  • Dendritic cells and sit ontop of the M cell or can extend through the peyers patch so they sample within the gut directly
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16
Q

what happens if you kill all the bacteria in the gut

A

leads to an immature Peyer’s patch

17
Q

how do T and B lymphocyte gut homing work

A
  • Peyers patch samples the kind of bacteria that we have, if there are harmful bacteria then we need to make B cells and T cells to destroy them
  • APC released and go into the lymph nodes
  • They need to go back into the gut
  • APC talk to naïve T cells and prim them to go to the gut
  • They use vitamin A – retinoic acid
  • They have alcohol dehydrogenases and retinal dehydrogenase which converts retinol to retinal first then to retinoic acid
  • It modifies the DNA of T cells to prim it to go to the gut
  • The retinoic acid tells the nuclei of the T cells to form Alpah4beta7 and CCR9
  • The APC cells have equipped the T cells with two receptors that allow them to go to the gut, they respond to signals that are only present in the gut
  • Endothelial cells in the gut and in the gut only express MadCAM (this is a singla from the gut telling the T cell to move to the gut) this is the ligand for alpha4beta7, it binds to the receptor, the T cells get stuck to the cells in the gut
  • They then go to the lamina propria,
  • In the lamina propria the intestinal epithelial cells (enterocytes) express CCL25 which is the ligand for CCR9 (chemokine) – the chemokine molecule makes the cell move
  • Its informed of the kind of bacteria that is in the gut
18
Q

in the gut what is the main immunoglobulin

A

IgA

19
Q

what shape is IgA

A

dimer in mucous secretions but not in plasma

20
Q

what shape is IgM

A

pentamer in plasma

21
Q

what happens to IgA when it is transported across the epithelium

A
  • IgA is activately transported across epithelium by the polymeric Ig receptor and is secreted with the gut where it becomes SigA and SigM
22
Q

what disease has an IgA deficiency

A

2% of people with coeliac disease has an IgA deficiency

23
Q

describe the IgA and IgM

A
  • Both contain an 18 amino acid Constant-region tailpiece with a cysteine residue essential for polymerisation
24
Q

what is the J chain in IgA and IgM necessary for

A
  • A single 15KDa “J chain” (the “glue” between two Fc regions of the antibody. Necessary for secretion outside the mucosa)
25
Q

what is the function of the mucosal antibodies

A
  • Secretory IgA (SIgA) serves as the first line of defense in protecting the intestinal epithelium from enteric toxins and pathogenic microorganisms.
  • SIgA promotes the clearance of antigens and pathogenic microorganisms from the intestinal lumen by blocking their access to epithelial receptors, entrapping them in mucus, and facilitating their removal by peristaltic and mucociliary activities
  • You can live without Immunoglobulin A
26
Q

why do lactation of breast milk some B cells leave Peyer’s patch and make IgA

A

because. ..
- Breast endothelium expressed MadCAM
- Breast epithelium expresses CCL25

27
Q

what does B cells (that were in the gut) do in breast milk

A
  • During lactation some B cells which leave peyer’s patch move to the breast and make IgA
  • Breast endothelium expressed MadCAM
  • Breast epithelium expresses CCL25
  • When it is there it activate B cells and this leads to antibody production and secretion so produces SigA and SigM
  • It is secreted into the milk which goes into the gut of the baby, the baby was previously IgA deficient
28
Q

if malabsorption happens in the economically developed world what has caused it

A

coeliac disease

29
Q

what is coeliac disease

A
  • Autoimmune disorder of the small intestine that occurs in genetically predisposed people
30
Q

what do people with celiacs disease have and what does it lead to

A
  • Over 95% of people with coeliac have the isoform of DQ2 or DQ8 of the human leukocytes antigen HLA-DQ (HLA is MHC in humans)
  • This leads to uncontrolled immune response, cytokine inflammation interleukins produced and a big surge of different antibodies
  • This will destroy the enterocytes and make it possible for the gut to form the vili

Metabolism (26 decks)

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