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Year 1: Alimentary System > 8. Infection & Immunology of the Gut > Flashcards

8. Infection & Immunology of the Gut Flashcards

1
Q

What is GALT?

A

Gut associated lymphoid tissue

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2
Q

The gut must be immunoreactive to?

A

Pathogens

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3
Q

The gut must have tolerance to?

A

Food antigns

Commensal bacteria

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4
Q

What is size of the microbiota in the gut?

A

10^14

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5
Q

What does immune homeostasis and normal healthy immune system require?

A

Bacterial microbiota

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6
Q

What is the GI Tract constantly in?

A

A state of restrained activation - tolerance vs. active immune response

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7
Q

How many major phyla of bacteria are there in the gut?

A

4

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8
Q

What kind of relationship is the one between our microbiota and ourselves?

A

symbiotic - They can break down certain carbohydrates

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9
Q

How does the number of bacteria change down the GI tract?

A

They increase - diversity also increases

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10
Q

How can the microbiota be affected?

A 
Infection
Diet
Xenobiotics (antibiotics)
Hygiene
Genetics
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11
Q

Define Dysbiosis

A

An imbalance between the types of organism present in a person’s natural microflora, especially that of the gut, thought to contribute to a range of conditions of ill health.

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12
Q

What defence mechanisms exist in the GUT?

A

Physical to prevent invasion
Commensal bacteria - occupy ecological niche
Immunological: following invasion - MALT and GALT

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13
Q

What physical defence mechanisms exist?

A

1) epithelial barrier, peristalsis

2) Chemical (enzymes, pH)

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14
Q

What are the components of the epithelial barrier?

A

Mucus, epithelial monolayer and paneth cells

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15
Q

How has the epithelial monolayer adapted against disease?

A

It has tight junctions and transports IgA

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16
Q

How has Panth cells adapted against disease?

A

Secrete anitmicrobial peptides e.g defensins

Antibacterial lysozyme

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17
Q

Where does MALT tissue exist in the oral cavity?

A

Tonsils

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18
Q

What do the tonsils contain?

A

MALT, high endothelial venules: First line of defence against anything inhaled

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19
Q

What are the two types of GALT?

A

Organised and not organised

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20
Q

Where are not organised GALT distributed?

A

Through out the tissue - particularly in the lamina propria

Also lots of lymphocytes the epithelial tissue

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21
Q

What are typical structures of organised GALT?

A

Peyer’s patches - small intestine
Caecal and colonic patches - large intestine

Isolated lymphoid follicles
Mesenteric lymph nodes

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22
Q

How much of the intestinal epithelium does intra-epithelial lymphocytes make?

A

1/5

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23
Q

What are the different types of intra-epithelial lymphocytes?

A

Conventional T cells - can migrate form other tissues
Unconventional T cells - resident express CD4, CD8 or gd T cell receptor
Other innate immune cells - NK cells

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24
Q

What are peyer’s patches?

A

Aggregates of B cell follicles with T cell areas around

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25
What are M cells?
Microfold cells - They sample antigens from the lumen of the gut to present to T and B cells
26
What is epithelium above Peyer's patch called?
Follicle Associated Epithelium
27
Where does the Peyer's patch drain?
Into lymph nodes
28
What are TDCs?
Transepithelial dendritic cells which can sample the antigen across the epithelium
29
Where are most of the Peyer's patches?
Small intestine - Distal ileum
30
In Peyer's patches what do B-cells express?
The mature naive B-cells express IgM
31
How are B cells in PP activated?
Cytokines
32
In PP what do B cells express when activated?
IgA
33
Where do activated B cells secreting IgA go?
Lamina propria - they mature to become IgA secreting plasma cells
34
What heavy chain does IgA have?
alpha
35
How abundant is IgA?
Second most abundant after IgG. Major secretory immunoglobulin
36
What is the structure of IgA in the blood?
Monomer
37
What is the structure of IgA in secretions?
Dimer
38
What is the function of IgA?
Protects mucosal surfaces from bacteria, viruses and protozoa
39
What holds the IgA dimer together?
J chain
40
How is secretory IgA formed?
1) Plasma Cell produces IgA in the lamina propria 2) The IgA binds to a Poly-Ig receptor on the basolateral surface of the epithelial cells 3) That triggers receptor mediated endocytosis 4) In the vesicle proteases cleave the poly-Ig receptor 5) Part of the poly-Ig receptor becomes part of the secretory IgA
41
What is the function of the section of poly-Ig on IgA?
It protects it and prevents it from being degraded
42
What is the difference in the mucus between the small and large intestine?
The mucus is slightly looser in the small intestine
43
How does extravasation of naive T cells into lymph nodes occur?
See MCD
44
Where do lymphocytes proliferate mostly?
In the mesenteric lymph nodes
45
Cells that are primed in the gut...
Go back to the gut
46
Describe imprinting
When lymphocytes meet their antigen in the gut. The antigen imprints them to express particular integrins and chemokine receptors which recognise when they are in gut. Once in the gut they leave the circulation and go into the propria lamina.
47
What is main molecule responsible for gut homing?
MAdCAM-1, mucosal addressin cell adhesion molecule 1: tissue specific
48
Where is MAdCAM-1 expressed?
On the endothelial cells of the gut
49
What do lymphocytes imprinted for the gut express?
The specific integrin which binds to MAdCAM-1
50
Which vibrio cholerae serogroups express the toxin?
O1 and O139
51
What is the transmission of cholera?
Ingestion of contaminated food and water
52
How do you diagnose cholera?
Bacterial culture from stool sample on selective agar
53
What are viral causes of infectious diarrhoea?
Rotavirus (children) | Norovirus (winter vomiting bug)
54
How many types of rotavirus are there?
5 types A-E. A is the most common in humans
55
Where does rotavirus replicate in?
Enterocytes
56
What type of vaccine is the rotavirus vaccine?
Live attenuated oral vaccine
57
What is the treatment for rotavirus?
Easily managed by oral rehydration therapy
58
How do you diagnose RNA viruses?
PCR
59
What does norovirus cause?
acute gastroenteritis - recovery 1-3 days
60
How is norovirus transmitted?
Faeco-oral transmission
61
How long is the infectious period of norovirus?
2 weeks
62
What is a common cause of food poisoning in the UK?
Campylobacter
63
What are the most common species of campylobacter?
Jejuni and coli
64
How many types ofdangerous Escherichia coli?
6 pathogen types associated with diarrhoea
65
What pathogen is often associated with antibiotic use?
Clostridium difficile
66
How can you manage C. Diff?
Faecal microbiota transplantation
67
What causes coeliac disease?
autoimmune response against gluten
68
What does coeliac disease cause?
The immune response causes reversible damage to epithelial layers
69
What is the cause of IBS?
Visceral hypersensitivity, triggered by stress/diet
70
What does IBS cause?
Functional disorder, little damage
71
How do you treat IBS?
Diet modification and manage stress
72
What are the 2 form of IBD?
Ulcerative colitis | Crohn's disease
73
What is cause of IBD?
It is a aberrant inflammatory response to microbiota
74
What does IBD cause?
Possible serious damage to GI tract
75
How do you treat IBD?
Anti-infammatory drugs, immunosupressants and surgery
76
Where does coeliac disease affect?
Upper small intestine
77
Where is UC found?
Colon
78
Where does CD found?
Anywhere in the GI tract - frequent in the small intestine
79
What is difference in the pattern of inflammation in UC and CD?
UC - continuous area of inflammation | CD - Patches of inflammatory damage
80
Can surgery cure UC and CD?
UC - maybe | CD - no, but can enhance quality of life
81
How much of the GI tissue is affected by UC and CD?
UC - damage to mucosa and submucosa | CD - entire intestinal wall to serosa may be affected
82
What are the three factors that can cause IBD?
Genetic background, immune system and environmental factors
83
What are the specific microbiota changes in Chrohn's disease?
Decrease in the diversity of the microbiota

Year 1: Alimentary System (15 decks)

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