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GI > Immunological Functions > Flashcards

Immunological Functions Flashcards

1
Q

How big is immune system?

A

approx 10^12 cells

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2
Q

Features of innate immune system?

A
  • Prevents infection + avoids disease
  • Non-specific
  • No memory
  • Mediated by: macrophages, epithelial barriers, secretions
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3
Q

Features of adaptive immune system?

A
  • Responds to infection + prevents disease
  • Highly specific response to targeted microbe
  • Memory
  • Mediated by: lymphocytes, antibodies
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4
Q

eg of systemic immunity?

A

Bone marrow, spleen, thymus lymph system, blood circulation

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5
Q

eg of mucosal immunity?

A

Mucous membranes : eyes, nose, mouth, lungs, gut, GU

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6
Q

Features of mucosal immune system?

A

-Mucosal surfaces: oral, nasal, lacrimal surfaces gastrointestinal tract, bronchial tract, GU, mammary glands
-Colonised by microbes
-Main route of entry for infectious microorganisms
-Large SA specialised for absorption :
gut ~ 200m2 skin ~2m2

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7
Q

Innate mechanisms of mucosal immune system?

A

mucin, peristalsis, antimicrobial peptides, proteins

eg lysozyme, lactoferrin, phagocytes

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8
Q

Adaptive mechanisms of mucosal immune system?

A

mucosal/secretory immune system

discriminates between harmful pathogens + harmless antigens – foods + commensal bacteria

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9
Q

eg of innate mucosal barrier?

A 
Natural barriers 
(eg stomach)
Mucin
Peristalsis
Proteolysis
Microvillus membrane or squamous cell
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10
Q

Immunological of mucosal barrier?

A

Secretory IgA/IgM

IgG

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11
Q

Role of gingival crevice?

A

epithelial layer of the gum that contains immune cells

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12
Q

Lymphoid cells in gut?

A
  • Intra-epithelial lymphocytes
  • Lymphocytes and macrophages scattered in the lamina propria
  • Peyer’s patches
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13
Q

How pathogens get across gut surfaces?

A

-Breach of epithelium via ulcer so pathogen is getting
into sub-lamina (connective tissue under epithelium)
-Langerhan cell have extensions that go out which sample in gut lumen
*pathogens enter + withdrawn back in macrophage
*pathogens adhere to extension + when macrophage moves off it brings in pathogen
-Peyer’s patches (collection of lymphocytes) that actively sample gut lumen

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14
Q

How’s peyer’s patch linked to outside lumen?

A

via M-cell which is doing sampling,

rest of top covered by epithelium

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15
Q

Diff types of lymphoid cell?

A

intra-epithelial lymphocytes
lymphocytes
macrophages
=scattered in lamina propria + Peyers patches

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16
Q

Describe peyer’s patch experiment

A

-injected antigen into gut area w/o Peyer’s patch, ligated
sides, stitched up
-injected antigen into gut area with a Peyers patch
-w/o Peyers patch = weak antibody response, upstream or downstream also weak response
-Peyer’s patch one = immune response, further up + down gut

17
Q

Role of M cell?

A

-Microfold appearance
-Sits on top, samples gut fluid lumen, sends it down to
lymphocyte underneath

18
Q

What can gain entry via M cells + eg?

A
  • Particles + 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
19
Q

Migration of immune cells from Peyer’s Patches?

A
  • pathogen + lymphocytes
  • triggers immune response
  • B-lymphocyte mature -> B-cell
  • migrate away from Peyers patch
  • drain to local lymph node
  • continue to mature
  • enter back into lymph circulation back into blood circulation
20
Q

Diff between mucosal vs systemic immune system?

A
  • Systemic immune system lymphocytes stay in blood circulation + produce antibodies
  • Mucosal lymphocytes come back to mucosal immune system back to gut they originally came from + upstream gut
21
Q

What’s common mucosal response?

A

encountering antigen at 1 mucosal site –> immunity across all mucosal sites eg immune response in gut, antibodies in saliva, tears but lymphocytes must move home to a secretory gland before they produce antibodies

22
Q

What are mucosal antibodies?

A
  • Mostly SIgA
  • Found in all secretions + breast milk
  • Provide passive immune protection in new-born
23
Q

Features of IgG in blood?

A

normal : light + heavy chain

24
Q

Features of serum IgA?

A

-Composed of light chain + heavy chain.
mucosal surfaces :
-2 structures dimerized with a joining protein can bind to 4 antigens so difficult for pathogens to burrow via mucosal surface
-Wrapped up by another protein called secretory component protecting antibody from degradation by proteolytic enzymes we produce or produced by bacteria

25
Q

Mechanisms of action of antibodies IgG in blood?

A
  • Bind to key functional sites on microbes + toxins to blocks its functionality
  • Agglutination
  • IgG induces inflammation, by activating complement pathway.
  • Recruits immune cells.
26
Q

Mechanisms of action of antibodies IgA in serum?

A
  • Block activity + agglutinate
  • Dosn’t induce inflammation in gut
  • Doesn’t bind immune cells
27
Q

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
28
Q

Systemic immune response to vaccines?

A 
-1st injection produce small antibody
response, 1 or 2 weeks to develop, then
it would die down
-booster injection produce massive response, mediated by IgG --> immunity, years for this antibody response to
decline
29
Q

Mucosal immune response to vaccines?

A
  • 2nd vaccine very similar + immunity takes a nosedive after
  • like having 2 primary responses
  • no memory
  • use GM plants for Hep B vaccine
30
Q

Oral vaccine delivery using GM plants?

A
  • hep B surface antigen gene transferred from yeast into plant cell (potato)
  • potato plants regenerated from transformed cells
  • hepatitis vaccine correctly expressed by potato plants
  • GM potatoes harvested that contain hepatitis vaccine
  • feed uncooked tubers to animals or humans
  • analyze immune response
31
Q

Oral tolerance?

A
  • Orally delivered antigens suppresses systemic immunity
  • If antigen 1st encountered through mucosal immune system then systemic immune system can be unresponsive (tolerised) to that antigen
32
Q

Practical considerations of oral tolerance?

A
  • Tolerance to dietary foods, breakdown to food allergy
  • Oral vaccination + safety
  • Treatment + prevention of autoimmune diseases
33
Q

Is oral tolerance a contra-indication for oral immunisation?

A
  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 μg range)
34
Q

SUMMARY

A
  • Mucosal immune system stimulated by antigens independently of systemic immune system
  • 2 immune systems not entirely isolated
  • Site of stimulation at specialised sites in GALT, BALT, NALT.
  • 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

GI (15 decks)

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