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POM Week 3 > Immune Evasion > Flashcards

Immune Evasion Flashcards

1
Q

What are the innate immune cells?

A 
Neutrophils
Eosinophils
Basophils
Dendritic cells
Macrophages
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2
Q

Main features of neutrophils

A

Most abundant leukocyte
Recruited to are of infection
Detect microbes
Perform effector functions

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3
Q

Why must neutrophil responses be balanced?

A 
Prevent infection 
Prevent damage (inflammation)
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4
Q

What do neutrophils do?

A 
Recruitment
Transmigration
Adhesion 
Priming
Chemotaxis
Activation
Phagocytosis/ Degranualtion
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5
Q

What are the three things Bacteria evade?

A

Antibody opsonisation
Complement opsonisation
Neutrophil Functions

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6
Q

What is Staphylococcus aureus?

A

Gram-positive bacterium
Lives harmlessly in nose
Opportunistic pathogen
Many mechanism to evade neutrophils

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7
Q

What is antibody opsonisation?

A

Antibodies bind antigens allowing:

  1. Deposition of complement in the classical pathway
  2. Neutrophils and other phagocytes the ability to detect invading microbes
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8
Q

How can Bacteria suppress opsonisation I?

A

Expresses capsule on its surface

Hides antigenic structure that can be detected by innate and adaptive immune components

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9
Q

Name some bacteria that express capsules

A

E. coli

S. aureus

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10
Q

How can Bacteria suppress opsonisation II?

A

S. aureus protein A binds IgG Fc region
Prevents normal opsonisation
Neutrophils cannot detect S.aureus

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11
Q

How can Bacteria suppress opsonisation III?

A

S. aureus SSL10 bind IgG to inhibit detection

Prevents the Fc receptors on neutrophils from detecting IgG on the surface of the bacteria

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12
Q

What are the three mechanism of suppressing opsonisation?

A

Capsule expression
Inhibit antibody opsonisation:
-SpA
-SSL10

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13
Q

What are other mechanism of suppressing opsonisation?

A

Proteases cleave antibodies: no stimulation of immune response
Antigenic variation

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14
Q

What are all the mechanisms to evade opsonisation?

A 
Hide antigens
Disrupt functions
Prevent detection
Degrade antibodies
Modify antigenicity
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15
Q

What is complement opsonisation?

A

Complement system is compose of a large no of proteins that react to opsonise pathogens or directly kill them by MAC formation

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16
Q

What are the key steps of the complement cascade?

A

Initiation
Formation of C3 Convertase
Formation of C5 Convertase
MAC Formation

17
Q

What does MAC do?

A

Produces pore on bacterial cell membrane

Causes lysis

18
Q

What is the mechanism of evading complement opsonisation I?

A

SCIN binds C3bBb and inhibits convertase production

19
Q

What is the mechanism of evading complement opsonisation II?

A

Efb binds C3d and inhibits fB binding C3 as it causes a conformational change

20
Q

What are the three complement evasion mechanisms?

A

Inhibit complement convertases
Inhibit C3 processing
Inhibit MAC formation

Proteases cleave complement components
Acquired host derived complement regulators- inactivate proteins

21
Q

How do neutrophils sense and respond to their environment?

A

Express 100s of receptors allows detection within environment

22
Q

What are pathogen recognition receptors?

A

Directly detect microbes or microbial products

Neutrophils are primed or activated

23
Q

What do immune receptors do?

A

Generate and modulate a balanced immune response

24
Q

What are the two types of immune receptors?

A

Activatory- enhance immune cell activity

Inhibitory- suppress immune cell activity

25
Q

How do bacteria evade neutrophil response I?

A

Bacterial CHIPs inhibits chemotaxis and activation
CHIPS binds C5aR and FPR1 and prevents binding of antagonist
Prevents recognition of neutrophils

26
Q

How do bacteria evade neutrophil response II?

A

Bacterial FLIPr binds Fc(gamma) receptors preventing the detection of IgG opsonised bacteria
Reduced antibody mediated phagocytosis

27
Q

How do bacteria evade neutrophil response III?

A

Kills neutrophils by releasing toxins

28
Q

How do bacteria evade neutrophil response (other)?

A

Bind inhibitory receptors, prevents activation of cells
Inhibit the effects of antimicrobials present in granules
Manipulate intracellular signalling
Modify bacterial surface

29
Q

How do bacteria evade neutrophil response (summary)?

A 
Inhibit chemotaxis
Inhibit detection of bacteria
Kills neutrophils
Stimulate inhibitory receptors 
Disrupt intracellular signalling
30
Q

What are the two types of diseases caused by S. aureus?

A

localised pyogenic “pus-producing”

disease mediated by toxins

31
Q

Under what conditions can S. aureus grow?

A

Can grow aerobically and anaerobically
Over a wide range of temperatures
High salt conc.

32
Q

Give some features of S. aureus?

A

Polysaccharide capsule to protect from phagocytosis

Cell surface proteins that mediate adherence of the bacteria to host tissues

33
Q

What enzymes do S. aureus use?

A

Catalase that protect from peroxides produced by neutrophils and macrophages
Coagulase converts fibrinogen to insoluble fibrin that forms clots and can protect S. aureus from phagocytosis
Hydrolytic enzymes and cytotoxins
Lipases, nucleases, and hyaluronidase that causes tissue destruction

34
Q

What toxins do S. aureus produce?

A

Enterotoxin- food poisoning
Exfoliative toxins A and B- scaled skin syndrome
Toxic shock syndrome toxin- mediates multi-organ pathology

35
Q

How can localised infections of S. aureus be managed?

A

Incision and Drainage

36
Q

How can systemic infections of S. aureus be managed?

A

Antibiotic therapy

Empiric therapy should include antibiotics against MRSA

37
Q

What is the drug of choice for IV therapy?

A

Vancomycin

POM Week 3 (11 decks)

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