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Physiology 1 > Immunological functions of the alimentary tract > Flashcards

Immunological functions of the alimentary tract Flashcards

1
Q

Compare and contrast the innate and adaptive immune system

A 
Innate
•	Prevents infection and avoids disease
•	Non-specific
•	No memory
•	Mediated by: macrophages, epithelial barriers, secretions…

Adaptive
• Responds to infection and prevents disease
• Highly specific response to targeted microbe
• Memory
• Mediated by:
• Lymphocytes, antibodies

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2
Q

What is systematic immunity?

A

Bone marrow, spleen, thymus lymph system, blood circulation

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3
Q

What is mucosal immunity?

A

Mucous membranes – eyes, nose, mouth, lungs, gut, genitourinary tract.

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4
Q

Give some examples of mucosal membranes?

What are they colonised by?

What can enter and why is there a large SA?

A
  • Mucosal surfaces: oral, nasal, lacrimal surfaces gastrointestinal tract, bronchial tract, genito-urinary tract and mammary glands
  • All sites are normally colonised by microbes
  • Main route of entry for infectious microorganisms
  • Large surface area specialised for absorption.
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5
Q

What are the innate mucosal barriers?

A

Innate:

  • Natural barriers
  • (eg stomach)
  • Mucin
  • Peristalsis
  • Proteolysis
  • Microvillus membrane or squamous cell
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6
Q

What are the immunological mucosal barriers?

A

Immunological:

  • Secretory IgA/IgM
  • IgG
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7
Q

Describe the sources of serum, saliva and local antibodies in the oral cavity

A

On image

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8
Q

What are the 3 lymphoid cells of the gut?

A
  1. Intra-epithelial lymphocytes
  2. Lymphocytes and macrophages scattered in the lamina propria
  3. Peyer’s patches
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9
Q

What are peyers pathes?

A

Peyer’s patches are small masses of lymphatic tissue found throughout the ileum region of the small intestine. Also known as aggregated lymphoid nodules, they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines.

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10
Q

What are M-cells and what do they uptake?

A

M cells are specialized epithelial cells of the mucosa-associated lymphoid tissues. A characteristic of M cells is that they transport antigens from the lumen to cells of the immune system, thereby initiating an immune response or tolerance.

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11
Q

What do M-cells target for uptake?

A

Particles and macromolecules: eg cholera toxin, latex particles, horseradish peroxidase, ferritin.

Viruses: eg poliovirus, HIV

Parasites: eg Cryptosporidium

Bacteria: eg Cholera, salmonella, Campylobacter Yersinia, Shigella, E. coli

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12
Q

Describe the migration of immune cells from Peyer’s Patches?

A

On image

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13
Q

Describe the common mucosal immune system

A

On image

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14
Q

What are the mucosal Antibodies:

A
  • Predominantly SIgA
  • Found in all secretions and breast milk
  • Provide passive immune protection in new-born infants
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15
Q

What is the difference between a serum IgG v Secretory IgA antibodies?

A

On image

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16
Q

Describe the Mechanisms of action of antibodies

A 
IgG
•	Binding to key functional sites	
•	on microbes and toxins	
•	Agglutination 	
•	Induce inflammation
•	Recruit immune cells

SIgA
• Binding to key functional sites on microbes and toxins
• Agglutination (much better)
Immune exclusion
Intra-cellular neutralisation
Virus excretion
Interactions with non-specific factors - lysozyme, lactoferrin, peroxidases

17
Q

What are the main approaches to Oral Immunisation?

A
  • Attenuated virus (eg polio)
  • Attenuated recombinant bacterial mutants (eg Salmonella typhi)
  • Mucosal adjuvants (eg cholera toxin)
  • Liposomes, microspheres,
  • Capsules
  • Transgenic edible plants
18
Q

Describe the systemic immune response to primary and secondary challenge

A

On image

19
Q

Compare systemic v Mucosal Antibody responses after immunisation

A

On image

20
Q

Describe Oral vaccine delivery using GM plants

A
  1. The Hep B surface antigen gene, is transferred from yeast into a plant cell (potato is used as a prototype).
  2. Potato plants are regenerated from transformed cells
  3. Hepatitis vaccine is correctly expressed by potato plants
  4. GM potatoes are harvested that contain the hepatitis vaccine
21
Q

How can we test the Concept of Oral Vaccine Production in Plants?

A
  1. Grow plants which express hepatitis vaccine to maturity and harvest edible tissue
  2. Feed uncooked tubers to animals or humans and analyze immune response
22
Q

What effect do orally delivered drugs have on systemic immunity?

A

• Orally delivered antigens can suppress systemic immunity
o natural mechanism to prevent immune reactions to food and useful commensals?
• If an antigen is first encountered through the mucosal immune system, the systemic immune system may become unresponsive (tolerised) to that antigen.

23
Q

What are the practical considerations of oral tolerance?

A
  • Tolerance to dietary foods, breakdown to food allergy.
  • Oral vaccination and safety
  • Treatment and prevention of autoimmune diseases
24
Q

Is oral tolerance a contra-indication for oral immunisation?

A

Induction of oral tolerance can depend on many factors, such as the nature of the antigen, dose and frequency of delivery.
1. Tolerance: Soluble antigens
Vaccination: Antigen/adjuvant or other formulations
2. Tolerance: Repeated sustained doses
Vaccination: Limited number of immunisations
3. Tolerance: High doses (eg 20-500mg bolus)
Vaccination: Low dose (usually in mg range)

25
Q

Mucosal Immune System Summary

A
  • The mucosal immune system can be stimulated by antigens independently of the systemic immune system. However, the two immune systems are not entirely isolated.
  • The site of stimulation is usually at specialised sites in GALT, BALT and NALT.
  • The major immunological factor is secretory IgA, which is expressed at all mucosal sites.
  • Most microbial infections start at mucosal sites, but most vaccines are administered systemically

Physiology 1 (72 decks)

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