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MBIO 3010 > Section 6 > Flashcards

Section 6 Flashcards

1
Q

What are some general way a pathogen can avoid the innate immune system?

A
  • Avoid phagocytic action
  • Interfering with ciliary action
  • Interfering with complement alternative pathway
  • Producing iron binding molecules
  • Blocking interferons
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2
Q

How can a pathogen avoid phagocytic action?

A
  • Release toxins
  • Prevent opsonization
  • Prevent contact
  • Inhibit phagolysosome fusion
  • Escape in cytoplasm
  • Release chemicals to resist killing once in phagocyte
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3
Q

How can a pathogen prevent opsonization?

A

Since antibodies tag a pathogen using the light chains and phagocytes identify the pathogen by binding to the heavy chain, if a pathogen can produce a protein that binds to the heavy chain of the antibody, opsonization will be prevented

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4
Q

How can a pathogen prevent contact?

A

Capsules

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5
Q

What is an example of a pathogen that interferes with ciliary action?

A

Bordetella pertussis

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6
Q

What does a pathogen with a capsule mean for the complement alternative pathway?

A

It will prevent either C activation or access to the fixed C3b

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7
Q

____ is resistant to MAC complex formation. How?

A
  • Bacterial membrane

- By shedding the part of the membrane that will attach to the other proteins in the MAC

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8
Q

Which part of bacteria activates the complement pathway?

A

Surface molecules

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9
Q

What iron-binding molecules can pathogens produce?

A

Transferrin

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10
Q

What is an example of a pathogen that produces iron-binding molecules?

A

Neisseria

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11
Q

Why is it more challenging to avoid the adaptive immune response?

A
  • B cells can recognize any shape

- Macrophages have intracellular microbes

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12
Q

____ are very good at avoiding immune defences

A

Viruses

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13
Q

What can lead to better survival in a host?

A

No extensive tissue damage

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14
Q

What does “hit and run” mean?

A

Microbe invades, multiplies, and sheds before adaptive immune system is activated

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15
Q

How can a pathogen conceal antigens?

A
  • Hide in host cells
  • Hide at sites not exposed to circulating lymphocytes
  • Molecular mimicry
  • Cover microbial surface with host molecules
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16
Q

What type of pathogens commonly hide in host cells?

A

Viruses

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17
Q

What are examples of sites in the body that are not exposed to circulating lymphocytes?

A
  • CNS
  • Joints
  • Testes
  • Placenta
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18
Q

What is an example of an infection that hides at a site not exposed to circulating lymphocytes?

A

Warts

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19
Q

What is difficult about an infection that hides at a site not exposed to circulating lymphocytes?

A

Immune cells can’t reach it, so in order to get rid of the infection, you must kill the host cells that it is present in

20
Q

What is released upon inflammatory response activation?

A

Lymphocytes, antibodies, and C

21
Q

What is retroviral RNA?

A

RNA viruses that can change their RNA to DNA once in a host cell

22
Q

What is molecular mimicry?

A

When a pathogen that infects someone has an antigen that is very similar to self-antigens

23
Q

Who does molecular mimicry benefit and who does it damage?

A

No benefit; damages host

24
Q

What is an example of a pathogen that covers microbial surface with host molecules?

A
  • Staphylococcus aureus - produces protein A that has a binding site for the Fc region of antibodies
  • If a phagocyte can recognize the free Fc region it will not initiate phagocytosis
25
Q

What are the 3 molecular mechanisms of antigenic variation?

A

1) Mutation
2) Recombination
3) Gene switching

26
Q

What is mutation?

A

Small changes in DNA system

27
Q

What is an example of a pathogen that undergoes mutation?

A
  • Influenza virus

- Genes encoding hemagglutinin and neuraminidase undergo mutation

28
Q

What does a mutation lead to?

A

Antigen change that makes them unrecognizable by B and T memory cells from previous infections

29
Q

What is antigenic drift?

A

Process that leads to small changes in antigenic structure caused by mutation

30
Q

What is recombination?

A

Mixing of segments of viruses

31
Q

What is antigenic shift?

A

A large change in antigenic structure caused by recombination

32
Q

When does gene switching occur?

A

During infection in the host

33
Q

What is gene switching?

A

When a pathogen switches its genes during infection, causing a need for antigens to change

34
Q

What pathogens infect T cells?

A

HIV, measles

35
Q

What pathogen infects B cells?

A

EBV

36
Q

What pathogen infects macrophages?

A

HIV

37
Q

What pathogen infects dendritic cells?

A

HIV

38
Q

What are examples of persistent infections?

A

Chicken pox, cold sores

39
Q

What are common forms of persistent infections?

A
  • Continuously infectious form
  • Low infectivity
  • Non-infectious forms
40
Q

In whom does reactivation typically occur?

A

Immunocompromised people

41
Q

What are the stages of reactivation?

A
  • Stage A - stimulus

- Stage B - spread and replication of pathogen

42
Q

What do decoy proteins do?

A

Divert complement components away from the bacterial surface, so the complement pathway can’t be activated

43
Q

What is an example of a virus that is a poor inducer of interferons?

A

Hepatitis B

44
Q

What is an example of a virus that produces molecules that block interferons in cells?

A

HIV

45
Q

It is better for a pathogen if they block or activate interferons and why?

A

Block because interferons are a means by which the host responds to DNA from infecting microbes

46
Q

What occurs in stage A of HSV reactivation?

A

Stimulated by sunlight, fever, or hormonal shifts

47
Q

What occurs in stage B of HSV reactivation?

A

Travels via sensory axons to skin/mucosal surface causing an infection of epithelial tissues and formation of a virus-rich vesicle (aka cold sore)

MBIO 3010 (17 decks)

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