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BIO 435: Virology > Immunity > Flashcards

Immunity Flashcards

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1
Q

What factors make up the triad model of disease?

A

host

environment

viral pathogen

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2
Q

How can the immune response to virus infections can be broken down into?

A

Nonspecific, innate immunity plays a role shortly after infection and is directed against any virus

Specific, adaptive immunity requires days to weeks before they are induced or effective in clearing specific viruses
- Slower but more powerful

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3
Q

What is the first line of defense against viral infections?

A

Apoptosis-programmed cell death (PCD)

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4
Q

Which gene helps regulate cell apoptosis?

A

p53

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5
Q

Which viruses target p53 to counteract apoptosis?

A

Adenovirus, HPV, and Hep B

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6
Q

What are the key components of the innate immune response?

A
  1. Cytokines
  2. Local sentinel cells
  3. Natural killer (NK) cells
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7
Q

What effect can IFN-a/b have?

A

IFN a/b: induce antiviral state

cells that are infected produce and release these cytokines
- these cytokines alert neighboring cells that a virus is
here (get ready, ramp up defenses)
- Like paul revere: the british are coming

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8
Q

What kinds of symptoms do interferons (cytokines) produce in host?

A

IFN production causes flu-like symptoms in infected host

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9
Q

When an IFN binds to a cell receptor, it triggers the expression of gene products that do what?

A

Block different stages of viral life cycle:

INHIBIT:
1) viral penetration and uncoating

  2) viral mRNA and protein synthesis

BLOCK:
3) virus genome replication

  4) assembly/release of new virions
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10
Q

How is an antiviral state established?

A

IFN produced and released from virus-infected cells ->

IFN binds to target cells ->

Signal transduction ->

Increased transcription of antiviral genes ->

Establishment of antiviral state

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11
Q

How were interferons discovered?

A

Isaacs and Lindenmann experiment:
- found some kind of interfering substance being
generated inside of cells against viruses

Step 1: get eggs ready and put egg cells into 2 different test tubes

Step 2: treat 1 tube w/ saline solution, added inactivated (killed) influenza virus into tube 2

Step 3: Allow tubes to incubate then infect both tubes w/ live flu virus, allow to incubate

Step 4: Measured both tubes to see how many new influenza virons were present
- Found less infectious particles in tube 2 (the one w/
inactivated virus added)

Some kind of interfering substance must be inhibiting the virus in tube tube, called these substances “interferons”

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12
Q

What are the stages of signalling from cytokines (or any chemical messenger)?

A

Primary Signal
Transduction (protein kinase phosphorylation)
Response

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13
Q

What antiviral proteins are expressed in response to IFN signaling?

A
  1. PKR activated by dsRNA
    • block protein synthesis
  2. 2’5’-oligo(A) synthetase is expressed and activates RNase L
    • degrades mRNA (no protein synthesis so no viral
      replication)
    • contributes to apoptosis
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14
Q

How does PKR activation prevent viral replication? What is an example of a virus that can get around IFN response in cells?

A

IFN activates Protein Kinase R (PKR)
-PKR phosphorylates eIF-2a which inhibits protein synthesis = blocking viral replication

HSV-1
- makes protein ICP34.5
- ICP34.5 directs host cell enzyme Protein Phosphatase 1a
to cleave the phosphate from eIF-2a that was inhibiting
protein synthesis
- Protein synthesis proceeds and viral replication can
occur

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15
Q

How do POX viruses get around IFN response?

A

POX viruses can make soluble proteins that are released from cells and bind IFN receptors on the cell’s surface (competitive inhibition)

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16
Q

What are local sentinel cells?

A

Macrophages and dendridic cells

  • Both professional APCs
  • can present w/ both MHC I and II
17
Q

WHat are the roles of dendritic cells in antiviral response?

A
  1. Directly inhibit virus replication through the production of IFN and other cytokines
  2. Trigger the adaptive T-cell mediated immunity to the virus by presenting viral antigens to TH cells.
18
Q

WHat are natural killer cells?

A

Participate in both innate and adaptive immune responses

NK cells are activated by IFNs and other cytokines and respond within minutes/hours

NK cells release perforins, granzymes and chemokines to kill virus-infected cells

19
Q

How are NK cells regulated?

A

NK cells constantly patrolling for infected cells

NK cells Have inhibitory and activating receptors

  • MHC molecules on host cell will bind receptor on NK
  • MHC + Inhibitory receptor = NK stands down

infected cells will down regulate MHC expression
- No MHC+inhibitory receptor binding = activating receptor binding = NK cell signalled to release perforin/granzymes to kill infected cell

Infected cells downregulate MHC I expression = good target for NK cells to kill b/c activating receptor binds

20
Q

What are the arms of adaptive immunity?

A

Two Arms of Adaptive Immunity:

1) Cell mediated Response
- T Cells
2) Humoral Response
- B Cells and antibodies they produce

21
Q

What Cells are involved in adaptive immunity?

A

1) T Cells
a) Cytotoxic T Cells (TCTL)
- induce apoptosis of cells that are infected w/ virus
b) Helper T Cells (TH)
- Help other cells w/ cytokine communication
- Need antigens to be processed and presented by
APC’s (macrophages & dendritic cells)
- activate B cells
- Help Tc
2) B Cells
a) Plasma Bodies
- produce Antibodies
- can recognize foreign antigen w/o any help
- antigen doesn’t have to be processed and
presented like T cells need

22
Q

What are the properties of adaptive immunity?

A

Slower to develop
Very Specific
Memory

23
Q

What is the difference between adaptive and innate immunity?

A

Nonspecific immunity plays a role shortly after infection and is directed against any pathogen

Specific immunity requires days to weeks before they are induced or effective in clearing specific viruses

24
Q

What are B Lymphocytes?

A

B lymphocytes are generated and mature in the bone marrow
- contain surface antibody receptors w/ high specificity for
specific antigen
- each B cell contains Ab’s for only one type of antigen

When they encounter an antigen they divide/differentiate into plasma bodies which produce HUGE quantities of soluble Ab’s
- After virus cleared some B cells form memory B cells

25
Q

What are T Lymphocytes?

A

T lymphocytes mature in the thymus gland
- Have Tcr (T cell receptor) which binds antigens
presented by APCs

T Helper cells contain co receptor CD4
- TCR recognize antigen present via MHC II

Cytotoxic T cells contain co receptor CD8
- TC activated when it’s TCR recognize antigen presented
via MHC I

26
Q

What role does the lymph system play in adaptive immunity?

A

Lymph supplies lymphocytes to the bloodstream

Lymphocytes congregate in the lymph nodes and exit through the outgoing lymph vessels

27
Q

Most cells of body contain which type of MHC?

A

MHC I

most cells of body don’t have MHC II

28
Q

How are B and T lymphocytes responsible for Specificity?

A

T Cell
each T cell recognizes a specificantigen associated with an MHC I (CD8 T-cell) or MHC-II (CD4 T-cell) receptor

B Cell
each antibody recognizes a unique antigen

29
Q

How are B and T lymphocytes responsible for Memory?

A

Once stimulated by antigen, a memory pool of T and B cells are established

30
Q

How are B and T lymphocytes responsible for Self-Nonself recognition?

A 
During development, T and B cells are selected that can
  recognize foreign (non-self) antigens but not self proteins
-prevent autoimmunity

BIO 435: Virology (18 decks)

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