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gastro > Gut Immunology > Flashcards

Gut Immunology Flashcards

1
Q

What is the massive antigen load in the gut formed of?

A

-Resident microbiota 10^14 bacteria
-Dietary antigens
-Exposure to antigens

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1
Q

How big is the GI tract?

A

200m2

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2
Q

What is restrained activation

A

-Tolerance (food antigens and commensal bacteria) vs active immune response (immunoreactivity - pathogens)
-Dual immunological role

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3
Q

What is bacterial microbiota required for?

A

Immune homeostasis of gut and development of healthy immune system

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4
Q

What is bacterial microbiota required for?

A

Immune homeostasis of gut and development of healthy immune system

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4
Q

What are the 4 major phyla of bacteria ?

A

Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria
-Also viruses and fungi

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5
Q

What do bacteria provide that we don’t have?

A

Traits that we have no had to evolve on or our own - genes in gut flora 100 times our own genome
-Essential nutrients
-Metabolism of indigestible compounds
-Defence against colonisation of pathogens

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6
Q

How does the host increase cell numbers

A
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7
Q

How does the host decrease cell numbers

A
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8
Q

What chemical digestive factors are produced by the host and what is the bacterial content ?

A

Host digestive factors decrease down the gut and the bacterial content therefore increases

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9
Q

What are symbionts?

A

Bacteria that live in the gut and cause no harm

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10
Q

What are commensals?

A

Live with the host but get an advantage by getting nutrients

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11
Q

What are pathobionts?

A

Can be tipped over to start harming the host

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12
Q

What is dysbiosis?
What can cause it?

A

Imbalance in the gut microbes

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13
Q

What does dysbiosis lead to?

A
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14
Q

What are microbiota?

A

Combination of organisms within a distinct anatomical niche

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15
Q

What are microbiomes

A

Composed of microbiota - all the genomes put together

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16
Q

What the types of physical mucosal defences in the gut?

A
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17
Q

What is commensal bacteria?

A

It occupies an ecological niche
Is a type of mucosal defence

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18
Q

What are immunological mucosal defences?

A
19
Q

How does the epithelial barrier work?

A
20
Q

Where is MALT found?

A

-Found in the submucosa below the epithelium, as lymphoid mass containing lymphoid follicles
-Follicles are surrounded by HEV postcapillary venules, allowing easy passage of lymphocytes
-The oral cavity is rich in immunological tissue
E.g. tonsils, adenoids

21
Q

What is GALT responsible for?

A

-Responsible for both adaptive & innate immune responses
-Consists of B & T lymphocytes, macrophages, APC (dendritic cells), and specific epithelial & intra-epithelial lymphocytes

22
Q

What is non-organised GALT made of?

A

Intra-epithelial lymphocytes
—–Make up 1/5th of intestinal epithelium, e.g. T-cells, NK cells
Lamina propria lymphocytes

23
Q

What is organised GALT made of?

A

Peyer’s patches (small intestine)
Caecal patches (large intestine)
Isolated lymphoid follicles
Mesenteric lymph nodes (encapsulated)

24
Q

How do Peyers patches work?

A
25
Q

What are the two ways in which Antigens can be taken up by the Peyers patch?

A

Via M cells or dendritic cells

26
Q

How do dendritic cells take up antigens?

A

By squeezing through tight junctions

27
Q

How does the B Cell Adaptive Response occur?

A
28
Q

How does the B Cell Adaptive Response occur?

A
29
Q

How is sIgA formed?
What does it do?

A
30
Q

What is lymphocyte homing and circulation?

A
31
Q

How does homing cascade direct circulating Naive T cells to PP’s Patches?

A
32
Q

Why do Enterocytes & goblet cells of the small bowel have a short life span (about 36 hrs) in comparison to the lifespan of weeks/months for other epithelial cell types (e.g. lung, blood vessels)

A

-Enterocytes are first line of defense against GI pathogens and may be directly affected by toxic substances in diet
-Effect of agents which interfere with cell function, metabolic rate etc will be diminished
-Any lesions will be short-lived
-If escalator-like transit of enterocytes is interrupted through impaired production of new cells (e.g. radiation) severe intestinal dysfunction will occur

33
Q

What was cholera caused by?
What is the mechanism for cholera?

A
34
Q

How is cholera trasmmitted?

A

Transmitted through faecal-oral route
—Spreads via contaminated water & food.

35
Q

What are the symptoms for cholera?

A

Main symptoms
—Severe dehydration & watery diarrhoea
Other symptoms
—Vomiting, nausea & abdominal pain.

36
Q

How is cholera diagnosed and treated?

A

Diagnosis: bacterial culture from stool sample on selective agar is the gold standard, rapid dipstick tests also available.
Treatment: oral-rehydration is the main management ; up to 80% of cases can be successfully treated.
Vaccine: Dukoral, oral, inactivated.
Globally 1.3 - 4 million cases, avg. 95,000 deaths/year (last indigenous UK case 1893: 2017 - 13 cases).

37
Q

What are Other Causes of Infectious Diarrhoea - Gastroenteritis

A
38
Q

What are rotaviruses?
Epidemiology?
Treatment?
Vaccinations?

A
39
Q

What are noroviruses?
Transmission?
Symptoms?
Diagnosis?
Epidemiology?

A
40
Q

What is campylobacter?
Transmission?
Treatment?
Epidemiology

A
41
Q

What are Escherichia coli (E. coli)?

A
42
Q

What is Enteroinvasive E. coli (EIEC)

A

-Shigella like illness
-Bloody diarrhea

43
Q

What is Enterotoxigenic E. coli (ETEC)

A

-Cholera like toxin
-Watery diarrhoea

44
Q

What is Enterohaemorrhagic or Shiga toxin-producing E. coli (EHEC/STEC)

A

-E. coli O157 serogroup, Shigatoxin/verotoxin
-5-10% get haemolytic uraemic syndrome: loss of kidney function

45
Q

Name 3 other E.coli?

A

Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)
Diffusely adherent E. coli (DAEC)

46
Q

What is the management of Clostridium difficile (C. Diff.)

A

gastro (6 decks)

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