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Alimentary System > 10. Infection and immunology > Flashcards

10. Infection and immunology Flashcards

1
Q

What are the 4 general functions of the gut microbiota?

A
  • Immune
  • Metabolic
  • Physiological
  • Trophic
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2
Q

What is oral candidiasis?

A
  • Yeast infection
  • From Candida albicans
  • Immunocompromised states e.g. HIV, chemotherapy
  • Treated via oral anti-fungals
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3
Q

What is Helicobacter pylori?

A
  • Gram negative microaerophilic rod
  • Gastritis or duodenal ulcers
  • Asymptomatic for 80%
  • Treatment with 1 week eradication therapy - proton pump inhibitor and amoxicillin
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4
Q

What is Travellers’ diarrhoea?

A 
• Acute gastroenteritis
• Caused by:
- E. coli
- Shigella
- Salmonella
- Cholera
- Rotavirus
- Norovirus
• Foeco-oral transmission
• Infections for 2 weeks
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5
Q

What is faecal transplantation and when is it used?

A
  • Transplantation of commensal flora

* Used in clostridium difficile

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6
Q

Describe the mucosal defence

A
  • Anatomical - barrier
  • Chemical - enzymes and low pH
  • Commensal bacteria
  • MALT
  • GALT
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7
Q

What does the epithelial barrier comprise (that plays a part in protection)

A
  • Mucosal layer - goblet cells
  • Epithelial monolayer - tight junctions, antimicrobial peptides, IgA transport
  • Paneth cells - crypts, defensins and lysosomes
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8
Q

Describe the GALT

A 
1) Organised sites
• Lymphoid tissue
- Peyer's patch in small intestine
- Mesenteria lymph nodules
2) Disorganised sites
• Lymphocytes in:
- lamina propria (IgA secreting B-cells)
- intra-epithelial cells (interstitial space)
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9
Q

How do the Peyer’s patches work?

A
  • Small intestine
  • Aggregated lymphoid follicles
  • Collection of naïve B and T cells
  • Covered by follicle associated epithelium (microvilli, no goblet cells)
  • M cells (+ APC) - transcytosis of lumenal bacteria, antigens and proteins, express IgA receptors
  • Naïve B cells express IgM
  • Antigen presentation => IgA
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10
Q

How does IgA work?

A
  • Up to 90% of B cells secrete it
  • Dimeric (SIgA) - IgA binds to BLm, receptor becomes secretory component, bound by J-chain, actively secreted
  • Transported through epithelial cells
  • Bind to luminal antigens
  • Prevents invasion and adherence of pathogens to mucosal wall
  • Doesn’t activate compliment
  • Most abundant “antibody” (IgG is the most abundant immunoglobulin)
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11
Q

What is the function of the secretory component?

A
  • Helps IgA move through enterocyte

* Protects dimer from enzymatic and acidic degradation

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12
Q

How does L-selectin (on lymphocytes) mediate rolling in HEVs?

A
  • Binds to mucosal addressin cell adhesion molecule-1 (MAdCAM-1)
  • Expressed on endothelial cells in lamina propria of small and large intestine
  • Enables recruitment in chronic gut inflammation
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13
Q

What are the symptoms of Irritable Bowel Syndrome?

A
  • Recurrent abdominal pain
  • Abnormal bowel motility
  • Constipation/diarrhoea
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14
Q

How is IBS treated?

A
  • Diet modification
  • Treatment of constipation - fibre etc.
  • Treatment of spasms and pain - anti-diarrhoeals, anti-muscarinic
  • Management of stress, anxiety and depression
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15
Q

What are the symptoms of Coeliac disease?

A
  • Abdominal distension (bloating)
  • Diarrhoea
  • Sometimes dermititis herpetiformis
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16
Q

Describe the mechanism of Coeliac disease

A
  • Gliadin (peptide component of gluten) not broken down in stomach
  • Reaches small intestine and binds to IgA
  • Gliadin-secretory IgA complex binds to the Transferrin receptor (TFR)
  • Transferred to the lamina propria
  • Tissue transglutaminase (tTG) cutes off amid group
  • Deamidated gliadin is phagocytosed by macrophages and presented (MHC II)
  • Activation of immune system - destruction of epithelial cells
17
Q

How can Coeliac disease be diagnosed?

A
  • Antibody blood tests - anti-gliadin, anti-tTg, anti-endomysial (EMAs)
  • Biopsy test of duodenum
18
Q

How can Coeliac disease be managed?

A
  • Gluten-free diet and medication

* Factors affecting compliance are lifestyle, eating out, cross contamination at home & holidays

19
Q

What are the symptoms of Crohn’s disease?

A
  • Pain in affected area (commonly right lower quadrant)

* Diarrhoea and bloody stool

20
Q

Describe the mechanism of Crohn’s disease

A
  • Triggered by pathogens e.g. mycobacterium, paratuberculosis, pseudomonas and listeria
  • Unregulated immune response => destruction of cells in the GIT
  • Gene mutations involve - frame-shift in NOD2 gene
21
Q

How can Crohn’s disease be treated?

A
  • Anti-inflammatory drugs and antibiotics
  • Severe - immunosuppressants e.g. corticosteroids
  • Surgical removal of affected tissue (doesn’t cure disease)
  • Liquid diet - if other mediacal therpies contraindicated, adjunctive with corticosteroids etc.
  • Low fibre/low residue, food reintroduction (to manage strictures if present, which can cause pain and gas)
  • Enteral tube feed or parenteral nutrition (IV) can be used to top up oral feeding post-surgery
22
Q

Why are food intolerance tests inappropriate for Crohn’s disease

A
  • No evidence for intolerance in Crohn’s

* Can result in food exclusion and nutritionally inadequate diets

23
Q

What are the symptoms of Ulcerative colitis?

A

• Pain in left lower quadrant
- ulcers along the inner surface of the large intestines (including colon and rectum)
• Severe and frequent diarrhoea (sometimes bloody)

24
Q

What is the mechanism of Ulcerative colitis?

A
  • Autoimmune
  • T cells destroy the cells lining the walls of the large intestine
  • Secondary cause - diet and stress
25
Q

How can Ulcerative colitis be treated?

A

• Anti-inflammatory drugs - sulfasalazine, mesalamine
• Severe - immunosuppressant e.g. corticosteroids, azathioprine, cyclosporine
• Colectomy
• Dietary manipulation
• Pre/probiotics
- treats and prevents pouchitis (colon removed leaving an inflamed pouch)
- helps remission
- prebiotics may cause abdominal pain, bloating, diarrhoea and flatulence
• Drink nutritious drinks, replace salt
• Soluble fibre helps absorption of water
• Avoid high fibre, gas producing foods, caffeine

26
Q

What are the symptoms of Cholera and how is it diagnosed?

A
  • Vomiting, nausea
  • Abdominal pain
  • Severe dehydration and diarrhoea

• Stool test - detect bacteria or antigen

27
Q

Describe the mechanism of Cholera

A
  • Vibrio cholerae transmitted through faecal-oral route (contaminated water and food)
  • Bacteria reaches the small intestine
  • Flagellum propels it towards the epithelial cell
  • Close contact - releases toxin
  • Toxin enters cell, biochemical reactions - exit of ions (Na+, K+, Cl-) and water from cell
28
Q

How can cholera be managed/treated?

A
  • Drink lots of fluids
  • IV fluids/antibiotics depending on severity
  • Drink clean water and eat clean food
  • Vaccination available

Alimentary System (15 decks)

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