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MIIM30011 Bacteriology > Immune System and Bacteria > Flashcards

Immune System and Bacteria Flashcards

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1
Q

What are some non-specific exterior defences against bacteria?

A
  • Skin (barrier, epithelium, fatty acids, lysozyme, microbiota)
  • Tears (lysozyme)
  • Urinary tract (epithelium, flushing, low pH, microbiota)
  • Mucosal Surfaces (epithelium, mucus, with lysozyme and lactoferrin, ciliated epithelial cells, microbiota)
  • Gut (epithelium, acid, defensins, microbiota)
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2
Q

How do cells of the innate and adaptive immune systems differ to each other?

A 
Innate	
Molecules:Shared by microbes/damaged host cells	
Diversity:Limited (encoded by germ line)
Memory:	None
Response:Rapid, constant size	
Barriers:	Skin, mucus, antimicrobial molecules
Blood proteins:Complement, etc.	
Cells:	Phagocytes, NK cells

Adaptive
Molecules:Antigens
Diversity:Large, somatic recombination possible
Memory: Yes
Response:Slower, more exposure increases size
Barriers: Lymphocytes (epithelia), antibodies
Blood proteins: Antibodies
Cells:Lymphocytes

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3
Q

What kinds of receptors distinguish self from non-self?

A

Pattern Recognition receptors (PRRs)

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4
Q

What are PRRs? What are examples of some?

A
  • Expressed by cells and soluble components of INNATE immune system
  • For PAMPs
  • TLR, NLR, RLH, collectins, scavenger receptors
  • Can bind DAMPs (molecular patterns produced by body during disease)
  • Binding lead to signalling cascades
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5
Q

What are PAMPs and DAMPs?

A

PAMPs: pattern associated molecular patterns
DAMPs: danger associated molecular patterns (produced by your body in response to disease)

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6
Q

What does the receptor CR1 on a phagocyte recognise on bacteria?

A

C3b

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7
Q

What does the receptor CR3 on a phagocyte recognise on bacteria?

A

iC3b

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8
Q

What does the receptor p150/95 on a phagocyte recognise on bacteria?

A

iC3b

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9
Q

What does the Fc receptor on a phagocyte recognise on bacteria?

A

Antibody

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10
Q

What does the C1q receptor on a phagocyte recognise on bacteria?

A

Mannose Binding Lectin

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11
Q

What does the Mannan receptor on a phagocyte recognise on bacteria?

A

Glycoconjugates

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12
Q

What does the Oligosaccharide receptor on a phagocyte recognise on bacteria?

A

Lectins

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13
Q

What does the PRR on a phagocyte recognise on bacteria?

A

PAMP

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14
Q

What does activation of the complement system result in? What are the 3 pathways?

A

• All lead to C3 convertase which activates C3 and allows for opsonisation (and activation of MAC)
• C3b is opsonin
• C5a
• Bacteria lysed by MAC (membrane attack complex)
• Lectin Pathway
o Collectins attached to mannose activate C2 and C4
• Classical Pathway
o Antibodies activate C1
• Alternative Pathway
o Bacterial surface molecules bind C3b

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15
Q

What is C3b?

A

Opsonin

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16
Q

What is C3a?

A

Helps chemotaxis, inflammation, B cell activation

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17
Q

What is the process of phagocytosis that kills bacteria?

A
  1. Engulf bacteria
  2. Phagosome formation, acidification
  3. Phagolysosome formation
  4. Death of bacteria by lysosomal proteins (degradative enzymes, defensins, myeloperoxidase)
  5. Release fragments
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18
Q

How does the timing of the release of cytokines and chemokines impact the immune response?

A
  • Early released up regulate response

* Late release down regulate response

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19
Q

What is the basic action of natural killer cells?

A
  1. Bind infected cell
  2. Release granules with toxic effectors (perforin, gransymes, granulysin)
  3. Kill bacteria and infected host cell
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20
Q

What occurs during the inflammatory response?

A
  • Complement activation
  • Cytokine release
  • Phagocyte transmigration and activation
  • Produce prostaglandins and leukotrienes
  • Symptoms = redness, swelling, heat, pain
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21
Q

What are the binding sites found on antibodies and where are they located?

A
  • Antigen binding sites in variable region (fv)

* Complement binding site and phagocyte receptor binding site in constant region (fc)

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22
Q

What is the role of secretory component?

A

anchor, protection from degradation

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23
Q

What is the action of CD8+ T cells?

A
  • Recognise antigen via MHC I on infected cell
  • Release toxic effectors (perforin, gransymes, granulysin)
  • Cell can apoptosis due to gransymes
  • Bacteria can be killed by granulysin
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24
Q

What is the difference between CD8+ T cells and Natural Killer Cells?

A

Natural killer cells recognise a cell is infected, but they don’t know what with

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25
What happens in the class MHC I antigen presentation pathway?
* All nucleated cells * Cytosolic protein * Intracellular bacteria (Cytotoxic/CD8 T cells)
26
What happens in the class MHC II antigen presentation pathway?
* Dendritic cells, macrophages, B cells * Endosomal proteins * Extracellular bacteria (T helper/CD4 cells)
27
What antigens use the CD1 pathway for antigen presentation?
• Lipid derived antigens
28
How does antigen presentation differ for intracellular and extracellular bacteria?
Intracellular use MHC I | Extracellular use MHC II
29
What encourages T cells to differentiate into Th1?
Il-12, IFNy
30
What encourages T cells to differentiate into Th2?
Il4, parasites
31
How does CD4 help B cells?
* MHC II * Epitope binds to antibody on B cell surface * Epitope broken up and presented * T cell recognises, production of memory cells and plasma cells
32
What is involved in CD4 independent B cell activation?
* No memory * Cross linking of molecules * IgG and IgM
33
Which bacterial structures are important in innate and acquired responses?
Cell wall, flagella, pilli, capsule
34
What happens as a result of PAMP-PRR interactions?
Lead to changes in cytokine gene expression and therefore inflammation
35
What does TLR1 and 6 interact with?
o Triacyl lipopeptide | o Peptidoglycan
36
What does TLR2 and 6 interact with?
o Diacyl lipopeptide
37
What does TLR3 interact with?
dsRNA
38
What does TLR4 interact with?
LPS
39
What does TLR7/8 interact with?
ssRNA | imidazoquinolones
40
What does TLR9 interact with?
o Cpg DNA | o Hemozoin
41
What does TLR5 interact with?
Flagella
42
What does TLR11 interact with?
Profilin like protein | Uropathogenic bacteria
43
Where are TLR 1, 2, 6, 4 and 5 located?
On the cell surface
44
Where are TLR 3, 7/8 and 9 located?
On the endosome
45
What are NLRs?
Nod like Receptors (i.e. inflammasome)
46
What does the ASC domain recruit?
Pro-caspase 1
47
What does activated caspase 1 do?
 Pre IL-1b to Il-1b (promotes inflammation) |  IL-18 activation (with IL-12 promotes IFN-g production)
48
What is an inflammasome? What domains does it have?
``` o NLRP (NLR subfamily with N terminal and PYD domain) o Sensor protein: NLR family o NACHT domain: NLR oligomerisation o PYD domain: signal transduction, caspase recruitment o ASC domain: adapter protein, recruits pro-caspase 1 ```
49
What does NLRP3 respond to?
Cell stress
50
What does NLRC4 respond to?
Flagella
51
What does NLRP1 respond to?
Anthrax LT
52
What does AIM2 respond to?
dsDNA
53
What are the features of the bacterial cell wall?
• Shape, support, structure, pathogenicity, protection, antibiotic action site, rigidity (peptidoglycan)
54
What is the structure of peptidoglycan? What PRRs recognise it?
o Repeating glycan chains cross linked by peptide fragments o Strong but flexible support framework o Recognised by TLRs and Nod1/2 o Made up of repeats of N-acetylmuramic acid and N-acetylglucosamine
55
Why is peptidoglycan a good target to select against?
 Unique to bacteria |  Needed for viability
56
What do oligopeptides do? What are they made of?
o Oligopeptides have L and D AAs (resistant to normal proteolytic enzymes) Crosslink glycan
57
What is the action of lysozyme on peptidoglycan?
Hydrolyses polysaccharide bonds
58
What are the 3 parts of LPS?
Lipid A (toxic), Core polysaccharide, O-specific polysaccharide side chain (distinguish strains)
59
What is the action of penicillin on peptidoglycan?
Prevents formation of trans-peptide bond
60
What are the features of gram positive cell walls?
o Thick peptidoglycan | Acidic polysacharides
61
What are teichoic acids and lipoteichoic acids? What are they required for?
``` o Acidic polysaccharide s  Cell wall maintenance  Enlargement of cell wall (cell division)  Acidic charge on cell surface  TLR recognition o Teichoic acid  Polymer of ribitol/glycerol and phosphate  Imbedded in peptidoglycan o Lipoteichoic acid  Attached to lipids in PM  Similar structure to teichoic acid ```
62
What are the features of a gram negative cell wall?
o Large periplasmic space o Thinner peptidoglycan o Outer membrane
63
What does the outer membrane of a G- cell wall contain?
 Protein  Lipoprotein  Phospholipid  LPS
64
What is LPS?
 Endotoxin |  Extended polysaccharide chains = receptors and antigens
65
How does our immune system respond to LPS?
o Immune reaction  Recognised TLR (TLR4)  Very immunogenic, antibodies protective o Toxic reaction  Lots of lipid A, increase temp, fever and shock, death possible o Endotoxic shock
66
What occurs in endotoxic shock?
 IL-1, IL-6, TNFa act on endothelial cells  Inflammatory response  Monocytes can release tissue factor (thrombotic and fibrinolytic response)  Endothelial damage  Loss of fluid in tissues, blood pressure falls, circulatory collapse, organ failure
67
What response does tissue factor stimulate during endotoxic shock?
thrombotic and fibrinolytic response
68
What are the features on O-specific polysaccharide chain in LPS?
o Chain of sugar molecules | o Identify strains
69
Which TLRs are activated by cell wall components?
1, 3, 4, 6
70
What is the role of glycocalyxes? What are they?
* Surround cell, sticky * Polysaccharide and/or polypeptides * Feature of blood borne pathogens
71
What types of glycocalyxes are there?
Capsule: organised repeating units firmly attached to cell surface • Slime layer: loose, water soluble
72
How do capsules protect bacteria?
* Protection from drying * Protect from phagocytosis * Prevent opsonisation * Promote adhesion * Promote biofilm formation * Poor antigens
73
What are flagella?
* Allow Motility for avoidance and favourable environment movement * 3 parts
74
What are the components of prokaryotic flagella?
o Long thin filament (flagellin units) o Hook o Basal body
75
How do flagella function?
360 degrees rotation • Movement in series of runs (single direction) • Movement in tumbles (random, adrupt) • Movement is in response to stimuli
76
How do we respond to flagella?
* Serology: H type antigen (TLR5) | * Activate intracellular NLRs
77
What are pili? What can they be used for and what is an example of a bacteria that uses pili?
* Non-motile extensions * Sticky, proteinaceous bristle like projection * Gram neg bacteria use for adherence, sticking to environment, sticking to mucous membranes * E.g. ETEC
78
What is the structure of pili?
* Rod shaped, hollow * Ordered helical protein subunit (pilin) array * Tip mediate adhesion * Tip can be pilin or other proteins * Tip for host/tissue septicity

MIIM30011 Bacteriology (5 decks)

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