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brs2 > Immunology of gut > Flashcards

Immunology of gut Flashcards

1
Q

what is the surface area of the gi tract

A

200m^2

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2
Q

what is the antigen load in gi tract

A

resident microbiota 10^14 bacteria
dietary antigens
exposure to pathogens

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3
Q

what is meant by state of ‘restrained activation’ in gi tract

A

has to balance tolerance with active immune response
tolerate: food antigens and commensal bacteria
immunoreactivity against: pathogens

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4
Q

what is the gut microbiota

A

considered a virtual organ
4 major phyla of bacteria - bacteroidetes, firmicutes, actinobacteria, proteobacteria, also viruses and fungi
provide traits we have not had to evolve on our own

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5
Q

what is dysbiosis

A

altered microbiota composition

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6
Q

what are some causes of dysbiosis

A 
infection and inflammation
diet
xenobiotics
hygiene
genetics
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7
Q

what are the physical barriers against pathogens

mucosal defence

A

anatomical - epithelial barriers and peristalsis

chemical - enzymes and ph

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8
Q

how does the epithelial barrier defend against pathogens

A

mucus layer - goblet cells
epithelial monolayer - tight junctions
paneth cell(small intestine) in bases of crypts of lieberkuhn
- secrete antimicrobial peptides and lysozyme

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9
Q

what is commensal bacteria

A

occupy ecological niche and act as barrier itself

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10
Q

what are some immunological defenses following invasion

A

malt - mucosa associated lymphoid tissue

galt - gut associated lymphoid tissue

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11
Q

what is malt

A
  • found in submucosa below epithelium as lymphoid mass containing lymphoid follicles
  • follicles are surrounded by HEV postcapillary venules - allowing easy passage of lymphocytes
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12
Q

what is galt

A

responsible for both adaptive and innate immune response through generations of lymphoid cells and antibodies

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13
Q

what are some examples of non organised galt

A

intra epithelial lymphocytes

lamina propria lymphocytes

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14
Q

what are some examples of organised galt

A

peyers patches(si)
caecal patches(li)
isolated lymphoid tissues
mesenteric lymph nodes - encapsulated

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15
Q

what are peyers patches

‘immune sensors’

A

found in submucosa of small intestine - mainly distal ileum
- aggregated lymphoid follicles covered with follicle associated epithelium
fae - no goblet cells, no secretory igA and lack microvilli

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16
Q

what is found in peyers patches

A

collection of naive t cells and b cells

  • development requires exposure to bacterial microbiota
  • 50 in last trimester foetus and 250 by teens
17
Q

how does antigen uptake via peyers patches take place

A

via microfold cells within FAE

M cells express igA receptors - facilitating transfer of igA bacteria complex into peyers patches

18
Q

what is the b cell adaptive response

A

mature naive b cell expresses igM in PPs
on antigen presentation class switches to igA
- t cells and epithelial cells influence b cell maturation via cytokine production
b cells further mature to become igA secreting plasma cells
populate lamina propria

19
Q

what immunoglobulin do upto 90% of gut b cells secrete

A

igA

secretory IgA binds luminal antigen - preventing its adhesion and consequent invasion

20
Q

why do enterocytes and goblet cells have short life span

A

can be directly affected by toxic substances in diet

- lesions will be short lived as responded to

21
Q

what is the mechanism of cholera

A

acute bacterial disease caused by vibrio cholerae serogroups o1 and o139
- bacteria reaches small intestine - contact with epithelium and releases cholera enterotoxin

22
Q

how is cholera transmitted

A

through faecal oral route

spreads via contaminated water and food

23
Q

what are the main symptoms of cholera

A

severe dehydration and watery diarrhoea

other symptoms: vomitting, nausea and abdo pain

24
Q

what is the diagnosis for cholera

A

bacterial culture from stool sample on selective agar is gold standard, rapid dipstick tests also available

25
Q

what is the treatment for cholera

A

oral rehydration is main management - upto 80% cases can be successfully treated
vaccine - dukoral, oral and inactivated
globally : 1.3 - 4 mill cases

26
Q

what are some viral causes of diarrhoea

A

rotavirus

norovirus - winter vomiting bug

27
Q

what are some bacterial causes of diarrhoea

A 
campylobacter jejuni
escherichia coli
salmonella
shigella
c. diff
28
Q

what are some protozoal parasitic casues of diarrhoea

A

giardia lamlia

entamoeba histolytica

29
Q

what are rota viruses

A

rna virus - replicates in enterocytes

5 types: A is most common in human infections

30
Q

what is the treatment for rotaviruses

A

oral rehydration therapy
still causes ~ 200000 deaths/yr
vaccine - live attentuated oral vaccine against ype a

31
Q

what is the norovirus

A

rna virus

incubation period 24-48 hrs

32
Q

how is norovirus transmitted

A

faecal oral transmission
individuals may shed infectious virus for upto 2 wks
outbreaks often occur in closed communties

33
Q

what are the symptoms of norovirus

A

acute gastroenteritis

34
Q

how to diagnose norovirus

A

sample pcr

35
Q

what are the most common species of campylobacter

A

c. jejuni and c. coli

36
Q

how is campylobacter spread

A

undercooked meat esp pultry
untreated water
unpasteurised milk
low infective dose

37
Q

what is treatment for camylobacter

A

non required usually
azithromycin
resitance to fluoroquinolones is problematic

38
Q

what is e coli

A

diverse group of gram neg intestinal bacteria
most harmles
6 pathotypes associated with diarrhoea

39
Q

what is the management for c diff

A

isolate patient
stop current antibiotics
give metronidazole and vancomycin
recurrence rate 15-35%, increasingly hard to treat
faecal microbiota transplantation - 98% cure rate

brs2 (65 decks)

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