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Virology > 9 Immune responses to viruses > Flashcards

9 Immune responses to viruses Flashcards

1
Q

what are the innate defences in innate immunity

A
  • Interferon
  • NK cells
  • Macrophages
  • Cytokines
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2
Q

what are the defences in acquired immunity

A
  • Humoral

- Cell mediated

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3
Q

what do the immune responses ideally do

A
  • protect
  • Irrelevant to ineffective parts of microorganism
  • harmful
  • counter protective
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4
Q

how should the immune responses protect

A

> sterilising (eradication)
concomitant (harmless symbiosis)
modulating (environment changed)

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5
Q

what is innate immunity

A
  • “natural” /’fixed”

> non- specific

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6
Q

what is active adaptive immunity

A
  • highly specific recognition
  • adaptive response, learning/memory aspect
  • antigen/antibody (humoral)
  • T cell involvement (cell-mediated)
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7
Q

what is passive adaptive immunity

A
  • (serum, colostrum)
    > cross over between innate and acquired system
    > cell mediated immunity
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8
Q

what happens in slow developing diseases

A

slow infection

transmissible agents ‘multiply’ without resulting in disease symptoms until cause fatal infection

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9
Q

what happens in chronic infection

A

after initial infection with or without disease symptoms infections virus released from host with no symptoms

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10
Q

what happens in latent infection

A

after initial infection, virus replicates in neurons in non-infectious state
virus activated to make new disease symptoms

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11
Q

what happens in acute infection

A

virus disappears after disease ends

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12
Q

what is the immune system overview for natural host resistance

A
  • Lack of pathogen receptors
  • Chemical or physical barriers
  • Innate Immunity
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13
Q

what are the innate defences

A

surface barriers

internal defences

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14
Q

what are the surface barriers

A

skin

mucous membranes

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15
Q

what are the internal defences

A 
phagocytosis
fever
NK cells
antimicrobial proteins
inflammation
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16
Q

what does early immune defence lead to

A

innate immunity

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17
Q

what leads to innate defences

A

barrier defences breached

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18
Q

what are interferons

A

“proteins secreted by virus infected cells”

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19
Q

what are interferons for

A

to protect non-infected

Stimulate T cell response

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20
Q

what are the types of IFN

A

type I

type II

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21
Q

which IFN are type I

A

IFNα: leucocyte IFN
IFNβ: fibroblast IFN
IFNτ/ε: trophoblast IFN
IFNλ and IFNκ (new groups)

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22
Q

which IFN are type II

A

IFNγ: Ag stimulation of NK and T cells

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23
Q

what does IFN-alpha and IFN-beta activate

A
  • Antiviral mechanisms in neighbouring uninfected cells

- Intracellular defences

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24
Q

what triggers the antiviral state

A

dsRNA

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25
Q

what is the IFN response

A
  • Antiviral protein
  • MHC-I molecules
  • NK activation
  • Apoptosis (induction)
  • Gene activation for Antiviral proteins
  • MHC I
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26
Q

what does MHC I molecules do in IFN response

A

Present viral peptide on infected cell surface to T cell

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27
Q

what are NK cells known as

A

LGL = “large granular lymphocytes”

28
Q

what are NK cells like

A

Like lymphocytes with more cytoplasm

29
Q

what does NK cells do

A 
Kill virus infected, and have some action against tumour cells
Recognize surface structure changes of infected cell
Require activation (very quick compared to the adaptive)
30
Q

what happens after NK activated

A
  • Release perforins
  • Induce apoptosis
  • Release IFNγ help activated acquired immune system
  • ADCC (~acquired)
31
Q

what is the activation of NK like

A

quick

32
Q

what is a macrophage

A

Phagocytosis virus + viral infected cell

33
Q

what do macrophages do

A

Killing (“cytotoxic”) of viral infected cell

34
Q

what does antiviral enzymes do

A

Induce mutation affecting RT => viral “death”

35
Q

what does tetherin do

A

Prevents budding of viruses by tethering virus and lipid membrane

36
Q

what does IFN do in viral count measures - stopped

A

Proteins to block production or activity

General gene expression inhibition (e.g. poliovirus)

37
Q

what does NK cells do in viral counter measures - stopped

A
  • Down regulation of MHC-I expression to avoid detection

- Altering/Non-expression of activator proteins on NK surface = inhibition of NK response

38
Q

what does tetherin do in viral counter measures - stopped

A

Vpu protein block expression/degrade of tetherin

39
Q

what is the high viral count for in acquired immunity

A
  • Ab non-neutralising
    > excess Immune complex
    > Immune complex deposits (tissue/fluid) Inflammatory response
40
Q

what is the ADE for in acquired immunity

A

“antibody dependant enhancement” of virus infection

- Macrophage uptake of poor neutralising Ab replication in macrophage ADE

41
Q

what is CTL’s activity in acquired immunity

A
  • Tissue damage where CTL’s infiltrate

- Some cases disease severity/death is result of CTL

42
Q

what is the auto-immune reaction in immune response damage

A
  • Tissue damage induces inflammation followed by:
  • Ag presentation of host’s own Ag (normally undetected)
    Or
  • Viral molecular mimicry of self-protein loss of immune tolerance to own tissue
43
Q

what is involved the humoral immunity - antibody structure

A
  • Antigen binding (Fab site)
  • Biological activity induction site (Fc)
  • Fc domain (H chain)
44
Q

what are the 5 types of antibodies

A
  • IgG
  • IgM
  • IgA
  • IgE
  • IgD
45
Q

what does IgG do

A

opsonisation

46
Q

what does IgM do

A

complement, opsonisation, agglutination, virus neutralisation

47
Q

what does IgA do

A

dimer

mucosal surface and secretion areas (sIgA)

48
Q

what does IgE do

A

acute phase Type I hypersensitive

helminth, protozoa

49
Q

what does IgD do

A

Relatively unknown

50
Q

what is the humoral immunity

A

B-cell produce Ab

IgM, IgG and IgA

51
Q

what does B-cell produce Ab for

A

anti-viral response

52
Q

what does IgM, IgG and IgA do

A

prevent spread between cells, tissues and blood stream

Prevent re-infection (site of entry)

53
Q

what is the effect of direct AB binding

A
  • Viral neutralisation

- Complement limited effect

54
Q

what are the AB mediated effects

A

Opsonisation viral infected cell
Complement activation
ADCC (Antibody Dependant Cell-mediated Cytotoxicity

55
Q

what is the Opsonisation viral infected cell

A

response by immune cells to Fc –receptor
Neutrophils + macrophages, NK cells
> Results in enhanced phagocytosis

56
Q

what is the complement activation in AB mediated effect

A
  • Destroy viral infected cells
  • Damage viral envelope (free virus)
  • Virus opsonisation enhanced phagocytosis
57
Q

what is the ADCC AB mediated effect

A
  • by ADCC “competent cells” (Tcytoxic, macrophage, NK)
  • Tcytoxic cells binds to Ab coated viral infected cell
    = perforin dependant killing of cell
  • Better at detecting infected cell than complement activation
    Note: involves both
  • humoral + cell-mediated response!
58
Q

what are the T-cell mediated responses

A

CD4+ T cell (T-helper cell)

CD8+T cell (CD8+ CTLs)

59
Q

what is the CD4+ T cell (T-helper cell) response

A
  • essential for B-cell/ Ab response
  • Induce CD8+
  • Ab more essential to prevent re-infection
60
Q

what is the CD8+T cell (CD8+ CTLs) response

A
  • Destroy virus infected cells
  • MHC-1 dependant: viral protein presentation
  • Perforin cytotoxic attack
  • “Clear” persistent infection through IFNγ and TNF
61
Q

what do cytokines do

A

immune ammunition/communication

62
Q

what makes IFNγ and TNFα

A

Produced by CD8 and CD4 Tcells

63
Q

what is IFNγ

A

Macrophage activator

64
Q

what does TNFα do

A

induction of

  • Intracellular IFN
  • Apoptosis
65
Q

what are the viral counter measures

A

Antigenic variation
IFN disruption
Cytokine
Chemokine disruption

66
Q

what does the antigenic variation do

A

able to rapidly change the virus particles on the surface – affect APC

Virology (15 decks)

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