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GI > GI Host Defense > Flashcards

GI Host Defense Flashcards

1
Q

What are some first lines of defense in the GI system? (Immediate)

A

Epithelium: physical barrier, ion transport (diarrhea)
Physiologic: pH, mucus, microbiota, lysozyme, antimicrobial peptides
Complement

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2
Q

What are some second lines of defense in the GI system? (early)

A

Phagocytes –> inflammation
Macrophages –> inflammation
Granulocytes –> anti-parasitic
NK cells –> antiviral

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3
Q

What are some components of the adaptive immunity of the GI system?

A

T cells: helper T cells (CD4)
Cytotoxic T cells (CD8)

B cells: IgA, IgG, IgE, IgM

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4
Q

What are the different T cell types involved in the adaptive immunity of the GI system?

A

Th1: IFN –> inflammation
Th2: IL4 –> anti-parasitic
Th17: IL17 –> inflammation

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5
Q

What are some roles of commensals in the GI system?

A
  1. Compete for resources with more virulent organisms
  2. Produce their own antimicrobial peptides (AMPs)
  3. Keep innate immune cells in an attentive state
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6
Q

What do defensins do?

A

Penetrate the lipid bilayer of bacteria and form pores

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7
Q

What are some examples of secretagogues?

A 
VIP
Acetylcholine
Substance P
Prostaglandins & leukotrienes
Histamine
Serotonin
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8
Q

What are some examples of inhibitors?

A

Norepinephrine

Somatostatin

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9
Q

How can CF lead to intestinal obstruction?

A

Mutations in the gene for cAMP-responsive apical anion channel –> near absence of electrolyte secretion

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10
Q

How does TGF-beta lead to restitutive epithelium?

A

It is fibrogenic agent – inhibits lymphocytes proliferation and also stimulates division, differentiation and migration of surrounding epithelial cells

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11
Q

What links the early innate responses with late adaptive immune response?

A

Dendritic cells

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12
Q

What cell types express TLRs?

A

Plasma membrane of epithelial cells, dendritic cells, macrophages, and PMNs

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13
Q

What PAMP do TLRs recognize?

A

Numerous bacterial, fungal and viral structures

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14
Q

What cell types express NLRs?

A

Cytoplasm of epithelial cells, macrophages, PMNs

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15
Q

What PAMPs do NLRs recognize?

A

Bacterial wall components (peptidoglycans)

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16
Q

What cells types express mannose receptors?

A

It is a membrane receptor on phagocytes that recognizes bacterial cell wall, carbohydrate and fungal wall glycans

17
Q

What are some examples of soluble recognition receptors?

A

C-reactive protein - recognizes microbial cell wall components
Mannose-binding lectin - recognizes bacterial cell wall carbohydrates
Complement-C3 - recognizes microbial cell walls
IgM - recognizes bacterial cell walls

18
Q

What is the function of TLRs?

A

Activate genes necessary for defense against the recognized bacterial, viral or fungal organism.

19
Q

Which intestinal bacterial infections are minimally invasive?

A

Campylobacter
Clostridium
Candida
Cryptococcus

20
Q

Which intestinal bacterial infections are invasive?

A

Listeria
Enteroinvasive E. coli

Opportunist: Clostridium, Shigella

21
Q

Which intestinal bacterial infections are toxigenic??

A

Enterotoxigenic E. coli
Vibrio cholerae

(Clostridium)
(Shigella)

22
Q

Alternative complement pathway

A

Cleave C3 protein binds bacterial surface

23
Q

Classical complement pathway

A

Ab (IgM, IgG) binds to bacterial surface

24
Q

Lectin complement pathway

A

Mannose binding lectin binds surface of bacteria

25
Q

What are some GI viruses that can lead to disease?

A

Rotavirus
Norwalk
Enteroviruses

26
Q

What are some intestinal parasites? How does our immune system respond to them?

A

Trematodes
Nematodes
Cestodes

*Too big to be phagocytes

27
Q

What type of cell is important in defense against helminth parasites?

A

Granulocytes: eosinophils, basophils, mast cells

*Non-phagocytic –> they defend the host by releasing their granule contents into the extracellular space

28
Q

How are granulocytes activated?

A

Ag-bound IgE binding cell surface FceRI

**So it depends on previous exposure to an Ag (sensitization)

29
Q

What are some things that granulocytes release?

A 
Vasoactive amines
Prostaglandins
Leukotrienes
Proteases
Cytokines

GI (34 decks)

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