immunity to viruses

Question 1

how do natural killer cells recognize infected cells

Answer 1

activating ligand and no MHC 1

Question 2

how do antibodies block free virus

Answer 2

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

Question 3

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

Answer 3

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

Question 4

what are strategies viruses use to evade host immunity

Answer 4

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

Question 5

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

Answer 5

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

Question 6

_____ uses decoy receptors to lure away cytokine stimulating ligands

Answer 6

smallpox

Question 7

what causes antibody dependent enhancement (ADE)

Answer 7

poorly neutralizing antibody

Question 8

what are the key players of the innate immune system

Answer 8

dendritic cells, macrophages, NK cells

Question 9

what are the 3 signals required for dendritic cells

Answer 9

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

Question 10

how do dendritic cells mature following antigen uptake

Answer 10

reduced phagocytosis, increased antigen presentation

Question 11

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

Answer 11

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

Question 12

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

Answer 12

nitric oxide (NO)

Question 13

NK cells are regulated by

Answer 13

the balance of signaling through stimulatory and inhibitory receptors

Question 14

NK cells lyse cells that lack ___

Answer 14

MHC class 1 (inhibitory receptors specific for MHC 1)

Question 15

how do NK cells kill infected cells

Answer 15

antibody-dependent cell-mediated cytotoxicity (ADCC)

Question 16

what are the type 1 interferons

Answer 16

TNFa and IFNb

Question 17

type 1 interferons are stimulated within hours of infection when ____

Answer 17

pattern recognition receptors recognize pattern associated molecular patterns on pathogens

Question 18

what do ISGs do

Answer 18

make interferons that inhibit viral entry, block viral replication

Question 19

what is a type 2 interferon

Answer 19

IFN gamma

Question 20

IFN gamma is produced by

Answer 20

NK cells and T cells

Question 21

what does IFN gamma do

Answer 21

activates macrophages and other innate cells

Question 22

how does antibody + complement block free virus

Answer 22

damage to virus envelope, blockade of virus receptor

Question 23

how does antibody + complement target virus-infected cells

Answer 23

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

Question 24

how does antibody bound to infected cells kill it

Answer 24

ADCC by NK cells, macrophage and neutrophils

Question 25

role of CD8 versus CD4

Answer 25

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

Question 26

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

Answer 26

CCR5

Question 27

mutations in CCR5 gene

Answer 27

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

Question 28

HIV recruits CD4 T cells only to __

Answer 28

infect and replicate within them

Question 29

RSV blocks _____ in the cells they infect

Answer 29

IFNa

Question 30

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

Answer 30

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

Question 31

what is latency

Answer 31

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

Question 32

what is immune privileged sites

Answer 32

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

Question 33

how do viruses render infected cells invisible to host immunity

Answer 33

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

Question 34

what is antigenic variation

Answer 34

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

Question 35

antigenic shift

Answer 35

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

Question 36

antigenic drift

Answer 36

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

Question 37

what is a mechanism to resist control by immune effector

Answer 37

soluble IFN receptors as decoys (smallpox)

Question 38

antibodies can form immune complexes resulting in _____

Answer 38

tissue damage

Question 39

virus induced damage

Answer 39

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

Question 40

molecular mimicry

Answer 40

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

Question 41

bystander activation

Answer 41

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

Question 42

epitope spreading

Answer 42

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

Question 43

example of molecular mimicry

Answer 43

coxsackie B virus-induced myocarditis