Alimentary System 8 - Infection & Immunology Flashcards Preview

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Flashcards in Alimentary System 8 - Infection & Immunology Deck (43)
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1
Q

What is restrained activation?

A

Seen in the gut, this is the balance between tolerance of food and commensal bacteria and the immunoreactivity with pathogens

2
Q

List the 4 major phyla of bacteria in the gut microbiota

A
  • Bacteroidetes
  • Firmicutes
  • Acinobacteria
  • Proteobacteria
3
Q

Define dysbiosis

A

Altered microbiota composition

4
Q

List the causes of dysbiosis

A
  • Infection/ inflammation
  • Diet
  • Xenobiotics
  • Hygiene
  • Genetics
5
Q

List the defences the mucosa has

A

Physical barrier

  • Chemical (enzymes/acidic pH)
  • Anatomical (epithelial barrier/peristalsis)

Commensal bacteria

Immunological (following invasion)

  • MALT (mucosa associated)
  • GALT (gut associated)
6
Q

List the mucosal defence in the epithelial barrier

A
  • Goblet cells + mucus layer
  • Epithelial monolayer with tight junctions
  • Paneth cells (secrete peptides and lysozyme in the SI)
7
Q

What is MALT?

A
  • Found in submucosa below the epithelium
  • Contains lymphoid follicles surrounded by high endothelial venules (postcapillary venules) allowing easy passage of lymphocytes
8
Q

List not organised GALT

A
  • Intra-epithelial lymphocytes

- Lamina propria lymphocytes

9
Q

List organised GALT

A
  • Peyers patches (SI)
  • Caecal patches (LI)
  • Isolated lymphoid follicles
  • Mesenteric lymph nodes (encapsulated)
10
Q

What is the function of GALT?

A

Both adaptive and innate immune responses through generation of lymphoid cells and antibodies

11
Q

Describe the structure of peyers patches

A
  • Mainly in the distal ileum
  • Covered with follicle associated epithelium (FAE)
  • FAE contains no goblet cells, secretory IgA and has a lack of microvilli
  • Organised collection of naive T and B cells
12
Q

What is the function of M cells?

A
  • Uptake antigens, and make IgA
  • Facilitates transfer of the IgA-bacteria complex into peyers patches
  • Found in the FAE
13
Q

How do peyers patches develop?

A

Following exposure to bacterial microbiota

14
Q

What is the full name of M cells?

A

Microfold cells

15
Q

How do transepithelial dendritic cells sample antigens?

A
  • The foot of the dendritic cell extends and samples antigens from the mucosa
  • They then take these antigens to the lymph nodes
16
Q

Briefly summarise the B cell adaptive response

A
  • Mature B cells express IgM in peyers patches
  • Upon antigen presention there is a class switch to IgA
  • T-cells and epithelial cells influence B cells maturation by cytokine production
  • B cells become IgA secreting plasma cells and populate the lamina propria
17
Q

What percentage of gut B-cells secrete IgA?

A

90%

18
Q

Compare the immune system in the small intestine and the large intestine

A
  • SI has deep folds, with peyers patches and paneth cells at the bottom of the crypt. LI has shorter crypts with no paneth cells
  • Resident macrophages under the epithelium in both
  • One layer of mucous. LI has two layers
19
Q

Describe the process of lymphocyte circulation

A
  • Made in primary lymphoid organs
  • Stored in secondary
  • Released into lymph nodes and enter circulation
  • There they may meet their antigen, or enter the lamina propria, skin or BALT
20
Q

Describe the process of gut homing

A
  • Lymphocyte rolls along the epithelium and is activated by binding of a4B7 integrin to MAdCAM1 on the membrane
  • This causes transmigration and chemotaxis
21
Q

Describe the mechanism of cholera

A
  • Bacteria disease caused by vibrio cholerae
  • Reach the small intestine and releases cholera toxin
  • Cholera toxin enters the epithelial cell and causes water and ions to leave the cell
22
Q

Describe the diagnosis and treatment of cholera

A
  • Diagnosed by growing bacterial culture on agar
  • Treated by rehydration
  • Vaccines can be used before going on holiday
23
Q

Describe the transmission of cholera

A
  • Feco-oral route

- Spreads through contaminated water and food

24
Q

List the symptoms of cholera

A
  • Severe dehydration
  • Watery diarrhoea
  • Vomiting
  • Nausea
  • Abdominal pain
25
Q

Describe the epidemiology of rotavirus

A

Most common cause of diarrhoea in infants and young children world wide

26
Q

What is the vaccination for rotavirus?

A

Rotarix

27
Q

How is campylobacter transmitted?

A

Undercooked meat, untrated waer, and unpasturised milk

28
Q

What antibiotic is used to treat campylobacter and why?

A
  • Azithromycin

- Due to ressitance to flouroquinolones

29
Q

How many pathotypes of E coli are there?

A

6

30
Q

How is C difficile managed?

A
  • Isolate patient
  • Stop antibiotics
  • Can use faecal microbiota transplantation
31
Q

List the infectious causes of diarrhoea

A
  • Cholera
  • E coli
  • C difficile
  • Rotavirus
  • Norovirus
  • Campylobacter
32
Q

Describe the mechanism of coeliac disease

A
  • Gliadin is not broken down in the stomach
  • It reaches the small intestine, binds to sIgA and is transferred to the lamina propria
  • Results in immune response
33
Q

List the symptoms of coeliac disease

A
  • Abdominal distention

- Diarrhoea

34
Q

List the methods used to diagnose and treat coeliac disease

A
  • Diagnosed by anti-gliadin blood tests and biopsy tests

- Treated by diet management

35
Q

Describe the mechanism of IBS

A
  • Visceral hypersensitivity

- Triggered by diet and stress

36
Q

List the symptoms of IBS

A
  • Recurrent abdominal pain
  • Abnormal bowel motility
  • Constipation and/or diarrhoea
37
Q

List the treatments of IBS

A
  • Modify diet (avoid apples, beans, cauliflowers)
  • Treat constipation (soluble fibre, stool softeners/laxatives)
  • Treat spasms and pain (anti-diarrheals, anti muscarinic)
  • Manage stress, anxiety and depression
38
Q

How can crohns and ulcerative colitis be differentiated?

A
  • Crohns affects the distal ileum and colon, while ulcerative colitis affects only the colon
  • Ulcerative collitis causes continuous inflammation, while crohns occurs in patches (cobblestone)
  • Ulcerative colitis can be cured by surgery
39
Q

Describe the mechanism of inflammatory bowel disease

A
  • Impaired barrier function due to diet, stress, smoking, and genetic factors
  • Leads to chronic inflammation and resulting destruction of tissue
40
Q

List the two inflammatory bowel diseases

A
  • Crohns

- Ulcerative colitis

41
Q

List the symptoms of inflammatory bowel disease

A
  • Bloody diarrhoea
  • Abdominal cramping
  • Anaemia
  • Weight loss
  • Fatigue
42
Q

How can inflammatory bowel disease be diagnosed?

A
  • Antibody tests
  • Endoscopy
  • Barium x-ray
43
Q

List the treatments for inflammatory bowel disease

A
  • Anti-inflammatory drugs
  • Immunosuppressants
  • Surgery (curative in ulcerative colitis but not in crohns)