9: Mucosal immunity 🏁 Flashcards

1
Q

3 major classes of mucosal tissue

A

respiratory/gastrointestinal/urogenital

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2
Q

Most deaths due to mucosal infection (class of infection + countries)

A

Acute respiratory infection lead to 4 million death, overall USA has most mucosal infection death (500k) followed by Brazil

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3
Q

What is the Waldeyer’s ring?

A

mucosal tissues around gut and airway bear lymphoid tissues (MALT) of tonsils and adenoids that form a ring

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4
Q

What are the first line defense mechanism of of immune system in the gut?

A

Mechanical
- epithelial cells joined by tight junctions
- longitudinal flow of air / fluid

Chemical
l- ow pH
- enzymes (peroxidase for radicals, lysouyme for murein, lactoferrin for Fe competition)
- antimicrobial peptides (alpha, beta-defensins, Cathelicidin, Histatin, S100 proteins) for membrane penetration and influence of bact. functions

Microbiological
- normal flora (commensals)

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5
Q

What are S100 proteins? Name example + function

A

Antimicrobial peptides like S100A7 (Psoriasin) that is produced by epithelial cells to protect against E.coli

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6
Q

Which 2 forms of IgA exists? Name function and characteristics o secretory IgAs

A
  • Monomeric and Dimeric form
  • Secretory IgA (dimeric) has 2 basic chains: J chain + secretory component
  • secretory component helps to transport dimer to mucosal cell surface + protects IgA from proteolytic digestion
  • monomeric form binds to CD89 on macrophages, neutrophils and eosinophils

Functions
- monomer: formes immune complexes and binds to CD89, activates APCs, induced cellular immune reaction
- dimer: neutralisation of antigens on mucosal surface, prevents attachement and movement of microbes, antigen transport across epithelium via poly-Ig receptor

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7
Q

How is IgA produced?

A

produced by plasma cells in lamina propria, derivee from B-2 cells in Peyer’s pacthes and B-1 cells in lamina prpria

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8
Q

Which cel transport antigen from mucosal barriers to lymph nodes?

A

DCs that migrate to epithelial layer and even extens into lumen to capture antigen, then migrate to myph nodes for antigen presentation

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9
Q

M cells: location, function

A

location: epithelial Peyer’s patches containing M cells with membrane ruffles

function: uptake of antigens by endo and phagocytosis, transportion of antigen across M cell in vesicles and release at basal surface, antigen can be bound by DCs to activate T cells

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10
Q

Which immune cells are located within epithelium ?

A

intraepithelial CD8+ lymphcytes that lie within epithelial lining

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11
Q

What is oral tolerance?

A

oral antigen administration can induce tolerance

  • immune system can learn to tolerate non-self antigens that are encountered in the gut
  • When antigens are ingested orally, they are exposed to specialized immune cells in the gut-associated lymphoid tissue, such as dendritic cells and T cells.
  • These cells can induce a state of immune tolerance by promoting the development of regulatory T cells, which suppress the activation of other immune cells that would normally attack the antigen.
  • Low tolerance + non-harmfull antgens like food proteins or commensals leads to stronger tolerance induction with only some local IgA production, no Absin serum, no t cell response and no memory
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12
Q

Give an example where commensals can induce disease?

A

Morbus Chrohn: a barrier disfucntion of intestinal mucosa leads to inflammation induced due to immune stimulation by commensals

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13
Q

Salmonella leads to mucosal infections. Name 3 ways.

How can Salmonella bacteria be killed?

A
  • enter and kill M cells, then infect macrophages and epithelial cells
  • invade luminal surface of epithelial cells
  • enter endrites of DCs that are extended to lumen

Killing by release of defensins by paneth cells that are specialized epithelial cells, granules contain prodefensin 5 and trypsin to activates prodefensin 5 due to cleavage

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14
Q

What is difference between immature and mature DCs and how is differentiation induced?

A

Immature DC induce tolerance of antigens, in presense of commensals, production of TGF.ß, … inhibits DC maturation, DCs weak signal leads to T cell differentiation into regulatory T cells

Mature DC induce T cell response, invasive microorganisms penetrate epithelium to mature DCs, activated DCs lead to differentiation into effector TH1 or TH2 cells

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15
Q

Is there another function that commensals offer?

A

some block TLR signalling by activating PPAR-y that removes NF-kappaB from nucleus or by blocking degradation of phosphorylated I-kappaB that prevents NF-kappaB translocation

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15
Q

Is there another function that commensals offer?

A

some block TLR signalling by activating PPAR-y that removes NF-kappaB from nucleus or by blocking degradation of phosphorylated I-kappaB that prevents NF-kappaB translocation

16
Q

Functions of TH1 and TH2 cells

Which effect is helpfull in helminths infection?

A

TH1
activate macrophages and produce IFN-G to activate B cells to produce IgGs

TH2
produce IL-13 for epithelial cell repair
UL-5 recruits eosinophils
drive B cells to produce IgE
drive mast cell recruitment

Helminths: TH2 protective effects, TH1 host damage