gut immunology Flashcards

(51 cards)

1
Q

what does it mean that the gut is in a state of restrained activatiom?

A

dual immunological role between tolerance and active immune response

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

what are the major phyla of gut bacteria?

A

bacteriodetes
firmicutes
actinobacteria
proteobacteria

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

host factors influencing bacterial cell numbers

A

nutrients (bacterial growth)

digestive factors, peristalsis, defecation (elimination of bacteria)

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

where is gut bacteria most prevalent and why?

A

colon

no digestive factors so numbers highest here, increases along tract

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

what is dysbiosis?

A

microbial imbalance (pathobionts and symbionts)

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

causes of dysbiosis?

A
infection and inflammation
diet
xenobiotics
hygiene
genetics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

types of anatomical mucosal defences in GI tract

A

Epithelial barrier

Peristalsis

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

factors produced by pathobionts contributing to disease development

A

TMAO
4-EPS
SCFAs
AHR ligands

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

what is the bacterial factor TMAO indicated in?

A

increased cholesterol deposition so athersclerosis

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

what are the chemical mucosal defences against pathogens in GI tract

A

Enzymes

Acidic pH

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

how do commensal bacteria form a mucosal defence?

A

occupy an ecological niche

act as second line to anatomical/chemical defences

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

what are the immunological mucosal defences of 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
13
Q

how does the epithelial barrier protect against infection?

A

mucus layer produced by goblet cells
tight junctions between epithelium
paneth cells (small intestine)

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

what is the role of paneth cells and their location?

A

small intestine, bases of crypts of Lieberkuhn

secrete antimicrobial peptides and lysozyme

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

what are MALTs?

A

mucosa associated lymphoid tissue esp in oral cavity

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

structure and location of MALTs?

A

below epithelium as a mass of lymphoid follicles
surrounded by high endothelial venules allowing easy passage of lymphocytes
oral cavity; linguinal tonsils, palatine tonsils, adenoid tonsils

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

what are GALTs?

A

gut associated lymphoid tissue
responsible for GI tract adaptive and innate response - B&T cells, macrophages, DCs, specific epithelial and intra-epithelial lymphocytes

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

what are organised GALTs?

A

peyers patches - distal ileum
caecal patches- large intestine
isolated lymphoid follicles
mesenteric lymph nodes

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

location of peyers patches?

A

distal ileum

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

what are non-organised GALTs?

A

intraepithelial lymphocytes

lamina propria lymphocytes

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

what are the nonorganised GALTs of small intestine?

A

intraepithelial lymphocytes - antimicrobial peptides
goblet cells
paneth cells
lamina propria

22
Q

what are the non organised GALTs of large intestine?

A

goblet cells
intraepithelial lymphocytes

no paneth cells like small i

23
Q

describe structure of peyers patches

A

aggregated lymphoid follicles underneath FAE (follicle associated epithelium) and M cells
sub epithelial dome of dendritic cells
B cells in follicle
naive t cells surround B cells

24
Q

what are M cells in peyers patches?

A

microfold cells
antigen uptake through them via IgA receptors
allow IgA-bacteria complexes to enter peyers patches

25
what are follicle associated epithelial cells?
cells overlying peyers patches | have no microvilli, goblet cells or IgA
26
how can antigen sampling occur in the GI tract
via M cells | OR independent of M cells by transepithelial dendritic cells
27
how do transepithelial dendritic cells sample antigens?
can open tight junction proteins and send dendrites to lumen of gut directly samples the bacteria and can transfer to mesenteric lymph nodes
28
describe the B cell adaptive response in the gut/GALT
mature (but naive) B cells express IgM on antigen presentation, class switch to IgA T cells and epithelial cells produce cytokines to influence maturation B cells then mature to be IgA producing plasma cells plasma cells then migrate and populate lamina propria
29
how does secretory IgA help immunological defence of gut
sIgA binds to luminal antigen, prevents adhesion and consequent invasion
30
how can circulating lymphocyte reenter intestinal GALTs?
process of lymphocyte homing
31
where do GALT lymphocytes travel after activation?
mesenteric lymph nodes to enter thoracic duct, enter broad circulation from there return to lamina propria (via lymphocyte homing) or move to peripheral lymph tissue
32
what is peripheral lymph tissue?
skin tonsils BALTs - bronchus associated lymphoid tissue
33
what is the process of lymphocyte homing?
lymphocytes in HEVs MAdCAM-1 on HEVs binds to lymphocyte 𝝰4β7 Integrin lymphocytes roll until tethered by MAdCAM-1 for activation and rolling arrest move through walls to lamina propria
34
why is there rapid turnover of enterocytes?
first line of defence - may be directly affected by toxic substances in diet therefore any agents affecting cell function die off and effect is diminished therefore any lesions will be short lived and not have long lasting effects
35
what bacteria is cholera caused by incl serotype
vibrio cholerae O1 and O139
36
MOA of cholera infection
Bacteria reaches small intestine → contact with epithelium & releases cholera enterotoxin enterotoxin internalised via retrograde endocytosis causes activation of adenylate cyclase to increase cAMP causes active secretion of salt and fluid (via CFTR) leads to watery diarrhoea via osmosis
37
transmission of cholera
faecal oral route - contaminated food and water
38
symptoms of cholera
severe dehydration and watery diarrhoea vomiting nausea abdo pain
39
how to diagnose cholera
bacterial culture of stool sample | rapid dipstick also available
40
what protections are there against cholera
vaccine - oral inactivated (Dukoral)
41
what viruses cause gastroenteritis
rotavirus in children | noravirus
42
rotavirus treatment (gastroenteritis)
oral rehydration therapy
43
what are rotaviruses
RNA viruses replicate in enterocytes subtypes A-E live attenuated vaccine against type A (most common)
44
what are noroviruses
RNA viruses faecal oral transmission usually outbreak in closed communities (cruises) cause acute gastroenteritis symptoms - recovery 1-3 days
45
what is the treatment for norovirus gastroenteritis
none required
46
what is campylobacter gastroenteritis
commonest UK cause of food poisoning low dose required for illness treatment typically not required
47
which pathogens causing gastroenteritis typically require no treatment?
campylobacter norovirus some e coli
48
clostridium difficle gastroenteritis facts
often due to long term antibiotics very contagious - isolate patient start metronidazole/vancomycin
49
treatments for clostridium difficile
metronidazole or vancomycin stop current antibiotics can give faecal microbiota transplantation
50
pathotypes of e coli causing diarrhoea
``` enterotoxigenic enterohaemorrhagic enteroinvasive enteropathogenic enteroaggregative diffusely adherent ```
51
transmission of campylobacter
undercooked meat esp poultry untreated water unpasteurised milk