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29 Cards in this Set
- Front
- Back
What is an important early defense mechanism against viruses that peaks within 1-3 days of viral infection
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NK cell response. They have broad specificity and will lyse a wide variety of virally-infected cells; they are not antigen specific and do not exhibit immunological memory
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How do NK cells kill
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They are characterized by their ability to recognize and kill virally infected as well as transformed cells. They express a broad array of activating receptors whose ligands are expressed on transformed and viral infected cells as well as in normal cells
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How do NK cells avoid killing normal cells
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They express inhibitory receptors that are engaged by ligands expressed on normal cells and are downregulated or absent in viral infected and transformed cells
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NK cells specialize in eradicating what type of cell
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Low MHC cells, which are for the most part abnormal. Also some viruses down-regulate MHC expression in host cells
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dsRNA causes infected cells to do what
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Produce type I interferons
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Which cells produce interferon-alpha
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B cells, monocytes and macrophages
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Which cells produce Interferon-Beta
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Fibroblasts and many other cells
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Early in viral infection, what binds to specific receptors on neighboring cells and induces an antiviral state
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Interferons alpha and Beta. An antiviral state means the cells are primed to respond if they themselves become infected and encounter dsRNA (viral replication intermediates)
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What does 2'-5' oligo (A) synthetase do when induced by interferons
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Leads to degradation of host and viral mRNAs
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What does Pkr (dsRNA-activated protein kinase) do when induced by interferon
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Phosphorylates and thereby inactivates the eIF2 translation initiation factor
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In addition to inhibiting viral protein synthesis, what else do interferons do
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Increase lytic potential of NK cells
Increase MHC class I expression |
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What three cell types are involved in adaptive immunity against viruses
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Antigen presenting cells (dendritic cells and macrophages), T cells, and B cells
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In cell-mediated immunity, what cytokine causes proliferation and differentiation of CTL precursors into CTL effector cells?
What is it produced by? |
IL-2, produced by T helper cells
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What two processes are necessary for activation of viral-specific CTLs
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Viral particles presented on MHC class I molecules (endogenous pathway)
IL-2 from T helper cells |
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What cytokine, which is released by activated CTL and Helper T cells, has direct antiviral activity by enhancing macrophages, CTLs and NK cells, and increasing MHC expression
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Interferon-gamma
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CTLs are activated to do what two things
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Lyse virally infected cells, and release interferon-gamma
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What pathway involves processing of viral particles by APCs, which allows presentation of viral peptides in association with MHC Class II antigens to T helper cells
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The exogenous pathway
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What five things are required for generation of anti-viral antibodies
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1: Activation of viral-specific T helper cells
2: Cytokine production to activate T and B cells 3: Binding of virus particles to B cells and expression of their MHC II 4: Proliferation and activation of B cells after interaction with activated Helper T cells 5: Secretion of Abs |
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What is the limitation of antibodies in the immune response to viruses
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They tend to recognize "whole" proteins, and viruses may never express surface proteins or only at late stages
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Why are T cells more effective than antibodies in the immune response to antibodies
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They can recognize portions of almost any viral protein when expressed in the context of MHC, even those made at very early stages
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What are the three strategies viruses use to evade antibodies
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1: Mutation of viral gene sequences by Antigenic Drift
2: Wholesale replacement of viral proteins by Antigenic Shift 3: Down-regulation of viral protein expression |
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Why are neurons a popular site of viral persistence
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They express little or no class I MHC
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What is the T2 protein of poxvirus
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A TNF receptor analogue, which will mop up TNF and prevent it from killing virally-infected cells
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What are the four main types of vaccine
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Killed, live-attenuated, subunit, passive
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What type of vaccine has inactivated viral nucleic acid but has not lost the immunogenicity of the viral proteins
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Killed-virus vaccines.
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What are the disadvantages of killed-virus vaccines
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Requires boosters (low antigenicity)
Incomplete inactivation of vaccine virus Induction of low IgA and CMI Potential for disease |
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What type of vaccine has a variant virus that replicates and produces the same antigens as virulent viruses, but no longer causes disease
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Live attenuated-virus vaccines. They are often achieved by serial passage in unnatural hosts or tissue cultures, which selects for mutations resulting in decreased virulence
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What type of vaccine has a component of the virus (a protein) known to be a protective antigen, that is made and used as the immunogen in the vaccine
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Subunit
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What type of vaccine has immunoglobulin preparations containing specific antibodies to the virus in question, as prophylatic or post-exposure treatments
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Passive immunization
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