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Immunology > immunity to viruses > Flashcards

immunity to viruses Flashcards

1
Q

how do natural killer cells recognize infected cells

A

activating ligand and no MHC 1

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2
Q

how do antibodies block free virus

A

block binding to cell, block entry into cell, block uncoating of virus

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3
Q

what is involved in CD8 T cell-mediated killing of virus infected cells

A

identify infected cells by recognizing MHC, release perforin/granzymes/other cytolytic proteins, trigger apoptotic cell death

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4
Q

what are strategies viruses use to evade host immunity

A

impairing host immune response, avoiding recognition by host immune defenses, resisting control by immune effector mechanisms

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5
Q

which mechanisms do viruses use to avoid recognition by host immune defenses

A

latency (produce little viral protein), hide in immune privileged sites, avoid T cell recognition by reducing MHC I expression, viral mutations

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6
Q

_____ uses decoy receptors to lure away cytokine stimulating ligands

A

smallpox

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7
Q

what causes antibody dependent enhancement (ADE)

A

poorly neutralizing antibody

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8
Q

what are the key players of the innate immune system

A

dendritic cells, macrophages, NK cells

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9
Q

what are the 3 signals required for dendritic cells

A

MHC:TCR, co-stimulation (CD80/86: CD28), cytokines

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10
Q

how do dendritic cells mature following antigen uptake

A

reduced phagocytosis, increased antigen presentation

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11
Q

what 3 levels do macrophages function at to destroy viruses and virus-infected cells

A

phagocytosis, killing of virus-infected cells, production of antiviral molecules (TNFa, NO, IFNa)

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12
Q

____ present in lysosomes is an important inhibitor of herpes virus and poxvirus

A

nitric oxide (NO)

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13
Q

NK cells are regulated by

A

the balance of signaling through stimulatory and inhibitory receptors

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14
Q

NK cells lyse cells that lack ___

A

MHC class 1 (inhibitory receptors specific for MHC 1)

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15
Q

how do NK cells kill infected cells

A

antibody-dependent cell-mediated cytotoxicity (ADCC)

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16
Q

what are the type 1 interferons

A

TNFa and IFNb

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17
Q

type 1 interferons are stimulated within hours of infection when ____

A

pattern recognition receptors recognize pattern associated molecular patterns on pathogens

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18
Q

what do ISGs do

A

make interferons that inhibit viral entry, block viral replication

19
Q

what is a type 2 interferon

A

IFN gamma

20
Q

IFN gamma is produced by

A

NK cells and T cells

21
Q

what does IFN gamma do

A

activates macrophages and other innate cells

22
Q

how does antibody + complement block free virus

A

damage to virus envelope, blockade of virus receptor

23
Q

how does antibody + complement target virus-infected cells

A

damage of infected cells (CDC), opsonization of coated virus or infected cells for phagocytosis

24
Q

how does antibody bound to infected cells kill it

A

ADCC by NK cells, macrophage and neutrophils

25
Q

role of CD8 versus CD4

A

CD8 kills infected cells, CD4 shapes the type of inflammatory response

26
Q

____ is a chemokine receptor involved in recruitment of macrophages and T cells to sites of infection

A

CCR5

27
Q

mutations in CCR5 gene

A

increases severity of west nile virus infection, required for HIV entry into cells so helps protect against HIV infection

28
Q

HIV recruits CD4 T cells only to __

A

infect and replicate within them

29
Q

RSV blocks _____ in the cells they infect

A

IFNa

30
Q

how does a chronic viral infection lead to T cell exhaustion (impairing host defenses)

A

as the viral load persists/increases, the expression of coinhibitory receptors such as PD1 and CTLA4 increases and causes suppression of T cells, they lose their capacity to proliferate and produce cytokines, they eventually undergo apoptosis

31
Q

what is latency

A

to avoid recognition by host immune defenses, minimal production of viral proteins makes the virus invisible to the immune system

32
Q

what is immune privileged sites

A

to avoid recognition by h9ost immune defenses, viruses hide in places like the brain where there is limited access to adaptive immune responses

33
Q

how do viruses render infected cells invisible to host immunity

A

they reduce MHC Class I expression on infected cells, thereby reducing CD8 T cell antiviral activity

34
Q

what is antigenic variation

A

a way to avoid recognition by host immune defenses, mutation of viral target allows escape from recognition by antibodies and T cells

35
Q

antigenic shift

A

abrupt, major change in the virus, new HA/NA; can occur when animal-derived viruses gain the ability to infect humans

36
Q

antigenic drift

A

small changes (mutations) in viral genes can lead to changes in viral surface proteins (HA/NA), which are the major antigenic targets of the immune system and vaccinations. changes occur continually over time and accumulate resulting in antigenically different viruses

37
Q

what is a mechanism to resist control by immune effector

A

soluble IFN receptors as decoys (smallpox)

38
Q

antibodies can form immune complexes resulting in _____

A

tissue damage

39
Q

virus induced damage

A

during some viral infections, tissues become damaged, provoking an inflammatory response during which hidden antigens become exposed and can be presented to the immune system to initiate an immune response

40
Q

molecular mimicry

A

a sequence in a viral protein that is homologous to a self-protein can be recognized, leading to a breakdown in immune tolerance to self-antigens

41
Q

bystander activation

A

self antigens are released from non-specific viral-mediated tissue damage

42
Q

epitope spreading

A

persistent infection releases hidden self-antigens that triggers autoreactive T cells

43
Q

example of molecular mimicry

A

coxsackie B virus-induced myocarditis

Immunology (10 decks)

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