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M2 GI/Nutrition > Host Defenses - Dwinell > Flashcards

Host Defenses - Dwinell Flashcards

1
Q

What host defenses are considered:

  1. Immediate?
  2. Early?
  3. Late?
A
  1. Immediate: Existing physical and chemical barriers
    • Skin / epithelium
    • Antimicrobial enzymes
    • Acid
    • Microbiota
  2. Early: Existing innate immune cells and mediators (cytokines, complement, etc.)
  3. Late: Adaptive immune cell and mediator response
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2
Q

Describe three ways in which commensal bacteria contribute to host defenses.

A
  1. Compete for resources with more virulent organisms
  2. Produce bacteriosins - their own antimicrobial peptides
  3. Keep host’s innate immune cells in an “attentive” state
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3
Q

How do antimicrobial peptides (including defensins and bacteriosins) work?

A

Form pores in the membranes of microbes, including bacteria, protozoa, fungi, and some viruses.

(Similar to the MAC in the complement system)

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4
Q

What cells produce defensins?

A
  • PMNs
  • Epithelial cells
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5
Q

How does lactoferrin contribute to host defense?

A

Sequesters free iron, which bacteria need

Can also oxidize (break down) bacterial cell walls

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6
Q

How does Tamm-Horsfall protein (THP) contribute to host defense? Where would you find a lot of this protein?

A

Inhibits uropathogenic E. coli from binding to the urinary tract epithelia

Abundant in the urine!

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7
Q

About how long does it take from the time an enterocyte is “born” (in an intestinal crypt) to migrate to the villus apex and be discarded into the intestinal lumen?

What is this process called and how does it benefit host defense?

A

5-6 days

Shedding

Microorganisms inside enterocytes (virsus, intracellular bacteria, etc.) are discarded relatively quickly - limits their spread

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8
Q

Genetic testing of discarded, apoptotic enterocytes in the feces is useful for what?

A

Testing for cancer

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9
Q

Why do some Cystic Fibrosis patients develop intestinal obstruction?

A

CF patients have a near total absence of electrolyte secretion, causing the intestinal lumen to not be well-lubricated

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10
Q

Name 6-7 substances that act as secretagogues (cause the secretion of another substance) in the intestinal tract

A
  1. VIP
  2. ACh
  3. Substance P
  4. Prostaglandins & Leukotrienes
  5. Histamine
  6. Serotonin
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11
Q

Name two substances that act to inhibit secretion (or promote absorption) in the intestinal tract.

A
  1. NE
  2. Somatostatin
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12
Q

What cytokine is important for restitution of the intestinal epithelium following an injury / disruption / ulceration?

Name three ways it contributes to the repair process.

A

TGF-ß

  • Fibrogenic
  • Inhibits lymphocyte proliferation
  • Stimulates surrounding epithelial cells
    • Division
    • Differentiation
    • Migration
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13
Q

What immune cell is especially important for linking the early innate immune response with the late adaptive immune response?

A

Dendritic cells

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14
Q

On what cell surface of the intestinal epithelium are Toll-Like Receptors (TLRs) found on?

A

Along the Basolateral Membrane, not the lumenal surface

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15
Q

Where in a host cell are Nod-Like Receptors (NLRs) located?

What does this make NLRs good at detecting?

A

Within the cytoplasm

Detect intracellular pathogens

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16
Q

What innate pattern recognition receptor (PRR) is unique to the membranes of phagocytes (i.e., not also found on epithelial cells)?

What PAMPs does it detect?

A

Mannose Receptor

Recognizes:

  • Bacterial cell wall carbohydrate
  • Fungal wall glycans
17
Q

Name four soluble PRRs.

What common defense pathway do all of these PRRs activate?

A
  1. C-reactive protein
  2. Mannose-binding lectin (MBL)
  3. Complement - C3
  4. IgM

Aside from any unique, individual effects -

All four can activate the complement system

18
Q

Name 2-4 bacteria that cause invasive infections of the intestines.

A
  • Listeria
  • Enteroinvasive E. coli

Opportunists:

  • Clostridium
  • Shigella
19
Q

Name 2-4 toxigenic bacteria that can cause intestinal infections.

A
  • Enterotoxigenic E. coli
  • Vibrio cholerae

(Also clostridium, shigella)

20
Q

Name four bacterial infections of the intestine that are typically minimally invasive.

A
  • Campylobacter
  • Clostridium (can invade oppotunistically)
  • Candida
  • Cryptococcus

[“I four-C a minimally invasive infection? Sorry…]

21
Q

What PRRs commonly detect bacteria?

A
  • TLRs 2, 4, 5
  • NLRs 1, 2
  • C3b
  • MBL
  • CRP
  • IgM
22
Q

What PRRs commonly detect fungi?

A
  • TLRs 3, 4, 5
  • C3b
  • IgM
23
Q

What secondary lymphoid structure would an activated dendritic cell travel to in order to present antigens to immature lymphocytes?

A

A Peyer’s Patch

(Or perhaps a regional lymph node that isn’t GALT-associated)

24
Q

Name the PRR that initiates the complement cascade in:

  1. The Classical Pathway
  2. The Alternative Pathway
  3. The Lectin Pathway
A
  1. Classical: IgM (pentameric)
  2. Alternative: Complement C3
  3. Lectin: Mannose-Binding Lectin (MBL)
25
Q

What PRRs are used to detect viruses?

A
  • TLRs 3, 7, 9
  • RIG1 (an NLR)
  • IgM
26
Q

In the early immune response, the pro-inflammatory cytokines IL1 and TNFa are produced primarily by what cell types?

A

Lecture says: Activated dendritic cells & activated PMNs

Wiki says: Predominantly activated macrophages

[/sigh]

27
Q

IFN gamma is predominantly produced by what immune cells?

A

T cells

  • Lecture stresses CD4+ (TH1 especially)
  • Wiki says both CD4+, CD8+

(Some by NK cells)

28
Q

Anti-parasitic granulocytes include what three cell types?

What activates these cell types? Name the ligand and the receptor.

A
  • Eosinophils
  • Basophils
  • Mast cells

Ligand: Ag-bound IgE

Receptor: Cell-surface FCeRI

29
Q

Why would a granulocyte contain granules of vasoactive amines?

A

Release of vasoactive amines stimulates smooth muscle contraction, which promotes parasite expulsion from the gut.

30
Q

In terms of ion transport, what is a typical mechanism of diarrhea employed both physiologically by the body and pathologically by toxin-producing microbes?

A

Active Cl- transport

Na+ and H2O follow

31
Q

Fill in the blanks:

TH1 cells produce the signature cytokine (1)_____, which is important for activation of (2)______ and production of (3)_______. This plays an important role in defense against (4)_______.

A
  1. IFNg
  2. Macrophages
  3. IgG
  4. Intracellular pathogens
32
Q

Fill in the blanks:

TH2 cells produce the signature cytokines (1)____, ___, and ___, which activate (2)________ and cause production of (3)______. This is important in the defense against (4)______________.

A
  1. IL-4, -5, and -13
  2. Granulocytes (eosinophils, mast cells)
  3. IgE
  4. Helminthic parasites
33
Q

Fill in the blanks:

TH17 cells produce the signature cytokines (1)_____ & _____, which aid in (2)______________. This is important for defense against (3)___________________.

A
  1. IL-17 and -22
  2. Neutrophilic & monocytic functions & inflammation
  3. Extracellular pathogens (bacteria & fungi)

M2 GI/Nutrition (43 decks)

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