Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BRS - Year 2 > 🍔Gastro🍔 - Immunology of the Gut > Flashcards

🍔Gastro🍔 - Immunology of the Gut Flashcards

1
Q

Why must the GI tract have “restrained activation” of the immune response?

A

Massive antigen load
Resident microbiota 1014 bacteria
Dietary antigens
Exposure to pathogens
Tolerance vs active immune response – Dual immunological role
Immune homeostasis of gut & development of healthy immune system requires presence of bacterial microbiota

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What must the immune system of the GI tract show tolerance and immunoreactivity to?

A

Tolerance - food antigens, commensal bacteria
Immunoreactivity - pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What 4 major phyla of bacteria exist in the gut?

A

Bacteroidetes
Firmicutes
Actinobacteria
Proteobacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What host actions lead to increased cell numbers in the gut microbiota?

A

Ingested nutrients
Secreted nutrients
Both lead to bacterial growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What host actions lead to decreased cell numbers in the gut microbiota?

A

Chemical digestive factors - bacterial lysis
Peristalsis, contractions, defecation - bacterial elimination (i.e. removal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What functions does the gut microbiota perform?

A

Production of essential nutrients
Metabolism of indigestible compounds
Defence against colonisation of pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is symbiosis?

A

living together, doesn’t imply either partner benefits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are symbionts?

A

organism that lives with a host without benefit or harm to either

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are commensals?

A

a microorganism which benefits from association but has no known effects on host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are pathobionts?

A

symbionts that don’t normally elicit an inflammatory response BUT under particular conditions (usually environmental) has the POTENTIAL to cause dysregulated inflammation & disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is dysbiosis?

A

Unhealthy (for whatever reason) gut microbiota

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can cause dysbiosis?

A

Infection/inflammation
Diet
Xenobiotics - small chemical compounds that enter the gut unnaturally e.g. drugs, pollutants etc…
Hygiene
Genetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is gnotobiology?

A

selective colonisation of germ-free animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the physical barriers of the mucosa?

A

Anatomical - epithelial barrier, peristalsis
Chemical - enzymes, acidic pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What role do commensal bacteria play in immune defence of the gut?

A

They occupy an ecological niche
They compete with potential pathogens for space and nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the immunological tissues present in the GI tract?

A

MALT (Mucosa Associated Lymphoid Tissue)
GALT (Gut Associated Lymphoid Tissue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the components of the epithelial barrier?

A

Mucus layer - goblet cells
Epithelial monolayer - tight junctions
Paneth cells (small intestine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are paneth cells?

A

Found in the bases of crypts of Lieberkühn
Secrete antimicrobial peptides (defensins) and lysozymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is MALT?

A

Mucosa Associated Lymphoid Tissue
Present in the submucosa below epithelial layers as lymphoid masses (e.g., follicles surrounded by HEVs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are HEVs?

A

high endothelial venules (HEV) postcapillary venules
help lymphocytes migrate from bloodstream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Outline the importance of HEVs

A

Immune surveillance: identify foreign invaders and changes in the body’s own cells, such as neoantigens in cancer
Lymphocyte recirculation: support high levels of lymphocyte extravasation from the blood.
Immune responses: help initiate and maintain immune responses in lymph nodes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the key MALTs in the oral cavity?

A

Palatine tonsils
Lingual tonsils
Pharyngeal tonsils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is GALT?

A

Gut Associated Lymphoid Tissue (GALT)
Responsible for both adaptive & innate immune responses through generations of lymphoid cells & antibodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the non-organised components of GALT?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the organised components of GALT?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Outline the non-organised GALT in the small intestine

A

Epithelium - goblet cells and intraepithelial lymphocytes
Crypts contain paneth cells
Lamina propria contains T cells, IgA B cells, macrophages, DCs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does the non-organised GALT in the large intestine compare to that of the small intestine?

A

No paneth cells in the crypts
Increased number of goblet cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are Peyer’s patches?

A

Found in submucosa small intestine – mainly distal ileum
Aggregatedlymphoid follicles covered with follicle associated epithelium (FAE)
Organised collection of naïve T cells and B-cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How do the naïve lymphocytes develop in the Peyer’s patches?

A

Development requires exposure to bacterial microbiota

30
Q

What is the follicle associated epithelium (FAE)?

A

Specialised epithelium that is associated with a follicle
No goblet cells, no secretory IgA, lack microvilli
Contain microfold (M) cells that allow antigen uptake

31
Q

What are M cells?

A

Microfold cells
Cells within FAE that express IgA receptors
Facilitate transfer of IgA-bacteria complexes into the Peyer’s patches

32
Q

How does antigen sampling occur independently of M cells?

A

Trans-epithelial dendritic cells

33
Q

How do trans-epithelial dendritic cells sample antigens?

A

Dendritic cells open up tight junctions proteins (they express their own proteins)
Send dendrites outside of the epithelium
Directly sample bacteria, transferring them to mesenteric lymph nodes

34
Q

What do mature naïve B-cells express in Peyer’s patches?

A

IgM

35
Q

What happens to mature naïve B-cells upon antigen presentation in Peyer’s patches?

A

Switches class from IgM to IgA

36
Q

What happens to B cells when they further mature?

A

T-cells and epithelial cells influence B-cell maturation via cytokine production
B-cells further mature to become IgA secreting plasma cells
Populate the lamina propria

37
Q

What is the function of secretory IgA?

A

sIgA binds luminal antigen
preventing its adhesion and consequent invasion

38
Q

How is IgA secreted into the lumen?

A
39
Q

Describe the lymphocyte circulation

A
40
Q

How do circulating lymphocytes re-enter intestinal tissue?

A

Lymphocytes in HEVs
HEVs express MAdCAM-1, lymphocytes express α4β7 integrin
Lymphocytes roll along HEV until they are tethered by MAdCAM-1
On binding there is activation and rolling arrest, followed by migration into the lamina propria

41
Q

How does the turnover of enterocytes compare to other epithelial cells?

A

Enterocytes & goblet cells of small bowel have a short life span (about 36 hrs)
Rapid turnover contrasts with lifespan of weeks/months for other epithelial cell types (e.g. lung, blood vessels)

42
Q

Why doe enterocytes have such a rapid turnover?

A

Enterocytes are first line of defence against GI pathogens & may be directly affected by toxic substances in diet.
Effects of agents which interfere with cell function, metabolic rate etc will be diminished due to elimination of cells
Any lesions will be short-lived

43
Q

What significance does the rapid turnover of enterocytes have pathologically?

A

If escalator-like transit of enterocytes is interrupted through impaired production of new cells (e.g. radiation) severe intestinal dysfunction will occur
(also rapidly dividing cells leads to higher risk of tumours/cancers)

44
Q

What is the mechanism of cholera infection?

A

Cholera - acute bacterial disease caused by Vibrio cholerae serogroups O1 & O139
Bacteria reaches small intestine → contactwith epithelium & releasescholera enterotoxin

45
Q

What effect does the cholera enterotoxin have?

A

Increases adenylate cyclase activity, increasing cAMP levels
Causes Na, K, Cl and HCO3 to leave cells, along with water
Leads too diarrhoea

46
Q

Outline the transmission and symptoms of cholera

A

Transmitted via the faecal-oral route - contaminated water and food
Main symptoms - severe dehydration and watery diarrhoea
Other symptoms - vomiting, nausea, abdominal pain

47
Q

How is cholera diagnosed and what is the treatment?

A

Diagnosis - bacterial culture from stool sample on selective agar, rapid dipstick tests also available
Treatment - oral-rehydration is main management, successfully treats 80% of cases

48
Q

What is the vaccine for cholera?

A

Dukoral, oral, inactivated

49
Q

What is gastroenteritis?

A

Infectious diarrhoea

50
Q

What are the causes other than cholera of gastroenteritis?

A

Viral - rotavirus (children), norovirus
Protozoal parasitic - Giardia lamblia, Entamoeba histolytica
Bacterial - Campylobacter jejuni, E. coli, Salmonella, Shigella, C. difficile

51
Q

What are rotaviruses?

A

RNA virus, replicates in enterocytes
5 types A – E, type A most common in human infections
Most common cause of diarrhoea in infants & young children worldwide.

52
Q

What is the treatment for rotaviruses?

A

Oral rehydration therapy

53
Q

What is the vaccination for rotaviruses?

A

Live attenuated oral vaccine (Rotarix) against type A

54
Q

Outline Norovirus (genus) Norwalk virus (species)

A

RNA virus, Incubation period 24-48 hours
Estimated 685 million cases & 200,000 deaths/year

55
Q

How is norovirus/norwalk virus transmitted?

A

Faecal-oral transmission
Individuals may shed infectious virus for up to 2 weeks, even after recovery
Outbreaks often occur in closed communities

56
Q

What are the symptoms of norovirus?

A

Acute gastroenteritis, recovery 1-3 days

57
Q

How is norovirus diagnosed?

A

Sample PCR

58
Q

Outline campylobacter

A

“curved bacteria”
Most common species:
Campylobacter jejuni, Campylobacter coli

59
Q

How is campylobacter transmitted?

A

Undercooked meat (especially poultry), untreated water & unpasteurised milk
Low infective dose, a few bacteria (<500) can cause illness

60
Q

What is the treatment for campylobacter?

A

Not usually required
Azithromycin (macrolide) is standard antibiotic
Resistance to fluoroquinolones is problematic

61
Q

Outline the epidemiology of campylobacter in the UK

A

Estimated 280,000 cases per year in UK, 65,000 confirmed
Commonest cause of food poisoning in the UK

62
Q

Outline Escherichia coli (E. coli)

A

Diverse group of Gram-negative intestinal bacteria
Most harmless
6 pathotypes associated with diarrhoea (diarrhoeagenic)

63
Q

What are the 6 pathotypes of E. coli?

A

Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enterohaemorrhagic or Shiga toxin-producing E. coli (EHEC/STEC)
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)
Diffusely adherent E. coli (DAEC)

64
Q

What are the symptoms of Enterotoxigenic E. coli (ETEC)?

A

Cholera-like toxin
Watery diarrhoea

65
Q

What are the symptoms of Enteroinvasive E. coli (EIEC)?

A

Shigella-like illness
Bloody diarrhoea

66
Q

What are the symptoms of 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

67
Q

What is the management for c. difficile?

A

Isolate patient (very contagious)
Stop current antibiotics
Metronidazole, Vancomycin
Recurrence 15-35%
Increasingly difficult to treat.
Faecal Microbiota Transplantation (FMT): 98% cure rate

68
Q

What are the 4 questions that should be asked in the clinical assessment of a patient with suspected gastroenteritis?

A

“When did it start?” – Onset of symptoms
“What does it look like?” – Amount, consistency and frequency​​
“How do you feel?” – Associated symptoms
“Where have you been recently?” – Travel, diet and lifestyle​​

69
Q

What onset of symptoms would suggest gastroenteritis?

A

Within one to two days of ingesting food suggests contaminated food

70
Q

What amount, consistency or frequency of stools suggests gastroenteritis?

A

Higher volume and/or frequency of watery stools
Blood, mucus and/or pus in stools suggest severe inflammation and/or infectious cause
Mucus and pus indicate a chronic inflammatory cause or infective pathogen

71
Q

What associated symptoms would you be looking in a case of suspected gastroenteritis?

A

Pain, bloating, nausea, vomiting, fever, tenesmus
Thirsty but no appetite

72
Q

What travel, diet and lifestyle factors may make someone more susceptible to developing gastroenteritis?

A

Recent travel or consumption of foods, such as meat, eggs, dairy or seafood, are suggestive of infection
Exposure to pets or cattle suggests infectious cause
Individuals who work in day care centres, hospitals or nursing homes suggests infection
Social history, such as sexual practice, alcohol use or drug use
IBD (prevalence 0.5–1.0%), coeliac (prevalence of 0.5–1.0%), IBS (prevalence 10.0–13.0%)

BRS - Year 2 (54 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions