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BRS Y2 > Immunology of the Gut > Flashcards

Immunology of the Gut Flashcards

1
Q

What does the antigen load in the gut consist of?

A

Resident microbiota
Dietary antigens
Exposure to pathogens

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2
Q

What does homeostasis of the gut involve?

A

Bacterial microbiota

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3
Q

What are the 4 major phyla of the gut microbiota?

A

Bacteroidetes
Firmicutes
Actinobacteria
Proteobacteria

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4
Q

Define dysbiosis

A

Altered microbiota composition

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5
Q

What are symbionts?

A

Microorganisms that live inside us with no effect, they aren’t gaining anything

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6
Q

What are commensals?

A

Microorganism that live in us and benefit from the host but don’t help the host

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7
Q

What are pathobionts?

A

Microorganisms that have potential to cause dysregulated inflammation

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8
Q

What affects the immunological equilibrium?

A

Symbiont, pathobionts and commensals

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9
Q

What are the 2 states in the immunological balance?

A

Regulation and inflammation

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10
Q

What are some causes of dysbiosis?

A 
Infection
Inflammation
Diet
Xenobiotics
Hygiene
Genetics
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11
Q

Why is dysbiosis significant?

A

It can have many effects on the rest of the body

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12
Q

What are the physical barriers in the mucosal defence?

A

Epithelial barrier

Peristalsis

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13
Q

What are the chemical barriers in the mucosal defence?

A

Enzymes

Acidic pH

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14
Q

What does the epithelial barrier consist of?

A

Mucus layer - Goblet cells
Epithelial monolayer - tight junctions
Paneth Cells

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15
Q

Where are paneth cells found?

A

Small intestine, bases of crypts of Lieberkühn

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16
Q

What do paneth cells secrete?

A

Antimicrobial peptides (defensins) & lysozyme.

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17
Q

Where is mucosa associated lymphoid tissue (MALT) found?

A

In the submucosa below the epithelium

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18
Q

What is the role of gut associated lymphoid tissue (GALT)?

A

Responsible for both adaptive & innate immune responses

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19
Q

What are non organised aspects of GALT?

A

Intra-epithelial lymphocytes

Lamina propria lymphocytes

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20
Q

What are organised aspects of GALT?

A

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

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21
Q

Where are Peyer’s patches mostly found?

A

Submucosa of the small intestine, mainly distal ileum

22
Q

What are the characteristics of follicle associated epithelium (FAE)?

A

No goblet cells
No secretory IgA
No microvilli

23
Q

What cells are involved in antigen uptake in FAE?

A

M cells

24
Q

How do M cells in FAE allow antigen/bacteria uptake?

A

They express IgA receptors, facilitating transfer of IgA-bacteria complex into the Peyer’s patches

25
Q

What do mature naive B cells express in Peyer’s patches? What happens after antigen exposure

A 
IgM
After antigen exposure the class switches to IgA
26
Q

What class of antibodies do gut B cells secrete?

A

IgA

27
Q

What is the role of IgA secreted by gut B cells?

A

They bind to luminal antigens preventing adhesion and consequent invasion

28
Q

In the gut where does antigen presentation and activation occur?

A

Peyer’s patches

29
Q

How does antigen presentation in Peyer’s patches lead to eventual lymphocyte honing and circulation?

A

After antigen presentation in Peyer’s patches they are - transferred to mesenteric lymph nodes where lymphocytes proliferate
Lymphocytes then go into circulation via thoracic duct
They can then enter the peripheral immune system and go to skin, tonsils etc via honing cascades

30
Q

What is the lifespan of gut enterocytes and goblet cells?

A

36 hours

31
Q

Why is the lifespan of gut enterocytes and goblet cells so short?

A

They are the first line of defense against GI pathogens & may be directly affected by toxic substances in diet

32
Q

Whats the mechanism of cholera infection?

A

Bacteria reaches small intestine and comes into contact with epithelium & releases cholera enterotoxin
This leads to eventual loss of Na+, K+, Cl-, Hco3- and water and diarrhoea

33
Q

How is cholera transmitted?

A

Faecal-oral (via contaminated water and food)

34
Q

What are the main symptoms of cholera?

A

Severe dehydration & watery diarrhoea

35
Q

How is cholera diagnosed?

A

Bacterial culture from stool sample

36
Q

How is cholera treated?

A

Oral rehydration

37
Q

What are some other causes of infectious diarrhoea besides cholera?

A

Viral (rotavirus/norovirus)
Protozoal parasitic
Bacterial (E coli, salmonella, shigella, c diff)

38
Q

What type of virus is rotavirus?

A

RNA

39
Q

Where does rotavirus replicate?

A

In enterocytes

40
Q

How is infection by rotavirus treated?

A

Oral rehydration

41
Q

Is there a vaccine for cholera?

A

Yes

42
Q

Is there a vaccine for rotavirus?

A

Yes

43
Q

What type of virus is novovirus?

A

RNA

44
Q

What is the incubation period for novovirus?

A

24-48 hours

45
Q

What are symptoms of infection by novovirus?

A

Acute gastroenteritis with recovery in 1 – 3 days

46
Q

How is infection by novovirus treated?

A

Treatment isn’t usually required

47
Q

How is infection by novovirus diagnosed?

A

Sample PCR

48
Q

Is E coli gram positive or negative?

A

Negative

49
Q

How may pathotypes of of E coli are associated with diarrhoea?

A

6

50
Q

How is c diff managed?

A

Isolate patient (very contagious)
Stop current antibiotics
Faecal Microbiota Transplantation (FMT) has a 98% cure rate

51
Q

Why is recurrent infection by c diff possible?

A

Even in intermediate recovery stages it doesn’t produce toxins but it is still invading so you can return to the previous state

BRS Y2 (85 decks)

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