Microbiota Flashcards

1
Q

Paneth cell anti-microbial peptides

A
Alpha-defensins
Lysozyme C
Phospholipase A2
RegIII-gamma
Cryptdin relates sequences (CRS)
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2
Q

Disrupt membrane integrity of microbes

A

alpha-Defensins

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3
Q

Hydrolyzes peptidoglycan in bacterial cell wall

A

Lysozyme C

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4
Q

Catalyzes hydrolysis of fatty acids in cell membrane

A

Phospholipase A2

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5
Q

Binds peptidoglycan, bactericidal against Gram-positive bacteria

A

RegIII-gamma

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6
Q

Antibacterial activity comparable to cryptdins

A

Cryptidin related sequences (CRS)

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7
Q

What are some of the pathogens strategies for evasion of AMPs?

A
Surface charge modification
Capusle formation
Modulate AMP expression
Efflux pumps
Protease secretion
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8
Q

What are some of the biological activities of IgA?

A
Inhibition of adherence 
Mucus trapping
Virus neutralization 
Enzyme and toxin neutralization 
Inhibition of antigen penetration
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9
Q

What are some ways microbes evade IgA?

A

Specific IgA proteases (meningitis assocation)
Other proteases (Porphyromonas gingivalis, Enterbacteriaceae)
Glycosidases (IgA heavily glycosylated and subject to damage)
IgA binding proteins

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10
Q

What are the 3 major classes of bacteria that exist in a healthy, balanced microbiome?

A

Symbionts: mutual relationship with known health promoting functions
Commensals: permanent resident, no benefit or harm
Pathobionts: calmness but have potential to induce pathology

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11
Q

Name some diseases associated with an altered microbial composition?

A
IBD
Autoimmunity 
Obesity
Diabetes
Asthma and allergy
Colorectal carcinoma
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12
Q

What are some factors that influence microbial composition of microbiota?

A

Non-immune factors: oxygen tension, pH, digestive enzymes, bile salts and mucus
Immune factors: defensins, IgA
Proposed mechanisms: create environment, provide selective nutrients, produce discriminating antimicrobials

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13
Q

How does oxygen tension change microbiota composition?

A

Increased oxygen tension is associated with increased abundance of facultative anaerobic bacteria

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14
Q

What role does the intestinal microbiome play in immune development?

A

Without bacterial colonization you get underdevelopment of lymphatic tissues, delayed B cell migration, reduced antibody diversity, reduced lymphocyte responsiveness

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15
Q

How do commensal bacteria help with the production and function of short chain fatty acids (SCFAs)??

A

Commensal bacteria ferment non-digestible dietary polyssarcharides to produce SCFAs – which regulate PMNs, dendritic cells, macrophages/monocytes, and intestinal epithelial cells; induce regulatory T cell differentiation; and regulate expression of virulence factors on bacterial pathogens

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16
Q

How do microbiota contribute to host protection?

A

They prevent pathogen colonization by:

  • bacteriocin production
  • SCFA production
  • Consumption of oxygen
  • Competition for nutrients
  • Competition for attachment sites
  • Induction of epithelial antimicrobials
  • Induction of mucus production and secretion
17
Q

Explain how antibiotics may contribute to C. diff infection?

A

Antibiotics kill many of the commensal bacteria that colonize the colon –> C. diff gains a foothold and produces toxins that cause mucosal injury –> Neutrophils and RBCs leak into gut between injured epithelial cells

18
Q

How do commensal bacterial regulate digestion?

A

They mediate bile acid synthesis, lipid absorption, amino acid metabolism, vitamin synthesis and SCFA production

Byproducts of commensal fermentation (metabolites) regulate the immune system

19
Q

What are some intestinal microbiome-disease associations?

A

Inflammatory bowel disease (Crohn’s)
Obesity and obesity related diseases (Diabetes, non-alcoholic fatty liver disease)
Cancer
Allergy/Asthma

20
Q

Explain how IBD is associated with microbiota.

A

IBD patients have abnormal bacterial colonization and immune function

Characteristic shift in microbial colonization from obligate anaerobic bacteria to facultative anaerobic species (proteobacteria) – associated with increased oxygen tension caused by inflammation

21
Q

What is a probiotic?

A

A viable microbial food supplement which beneficially influences the health of the host – improves intestinal barrier function, stimulates mucin secretion, stimulates antimicrobial peptide expression, enhances IgA production, anti-inflammatory activity

22
Q

How are probiotics being used in the treatment of immune disorders?

A

Restoring a healthy biota
Restores barrier function
Skew T cell immune responses to Th1 type