Host Response Flashcards
Recepter on the NK cell that binds to the MHC molecule on normal cell
Inhibitory receptor
Leukocyte interferon, produced in large quantities by plasmacytoid dendritic cells and is not host specific
INF-Alpha
When is gene silencing used?
Cells can utilize this mechanism to disrupt virus replication through production of RNAi that are complementary to specific viral genes
Antigenic Plasticity
Rapid changes in the structure of the viral antigen, may be the result of mutation, reassortment or recombination
(RNA/DNA) viruses are stronger inducers of Interferons
RNA
Possess potent antiviral, immunomodulating and anti-cancer properties
Interferons
NK cells recognize what molecules on healthy cells that keeps them from becoming activated
MHC Class I Molecules
Innate immune system responds in what ways when their PPRs are bound by a PAMP
Expression of interferons and inflammatory cytokines
Activation of phagocytic cells, increased production of inflammatory cells
Macrophages begin chemotaxis bringing neutrophils to site of inflammation
Interferon
Group of cytokines that are secreted by somatic cells in response to viral infections and to other stimuli
Ways in which Host responds to viral infection
Innate immune response
Adaptive immune response
Passive immune response
Natural Killer Cells
Large lymphocytes that are defined by their cytoplasmic granules, provide early and non specific resistance against viral infections
Virokines
Proteins synthesized by viruses which are homologs of cytokines/interferons
Ways that viruses evade host immune system
Antigen plasticity
Antigenic Multiplicity
Negative Cytokine Regulation
Down Regulation of MHC I Pathway
Inhibition of complement activation
Evasion of neutralizing antibodies
Latency
Cell to Cell spread
Inhibition of apoptosis
Humoral Immunity
Antibodies may be directed against viral proteins on free virions or against viral proteins expressed on surface of infected cells
CD4+ Th Cell mechanism of action
- Th interacts with microbial antigen in phagocyte
- Stimulates the release of cytokines
- Results in activation of macrophages, inflammation and Stimulation of B lymphocytes
Cellular immunity is mediated by
T Lymphocytes
Immunoregulatory interferon produced by antigen stimulated by T cells and NK cells. Labile at pH of 2 and demonstrates host specificity
Type II Interferon - Interferon Gamma
Defense exhibits neither antigen specificity nor memory
Innate Immunity
Components of adaptive immunity
Humoral Immune Response
Cellular Immune Response
Paracrine
Infected cell secretes IFN which acts on adjacent cells
Temperature of the nasal passages
33C
Gene Silencing
Cells utilize small, interfering RNA molecules (iRNA) to silence genes as a means of regulating normal developmental and physiological processes and potentially to interfere with virus replication
Interferons are inactivated by what route of administration
Oral
Innate immunity provides critical line of defense against viral infections because:
Constantly present
Operational immediately
Available for the first few days after viral infection
Temperature of the alveoli
37C
Fibroblast interferon secreted by virus-infected fibroblast, generally host species specific
INF - Beta
Granulocytosis
Presence in peripheral blood of increased number of granulocytes
Pathogen Associated Molecular Patterns
Macromolecues present in viruses and other microbes, but not on host cells
Antiviral effects of antibodies
Reduced damage to host from inflammatory response
Generation of oxidants
Immunomodulation
Opsonization
Activation of complement
Virus and toxin neutralization
Antibody dependent cell cytoxicity
Direct antimicrobial activity
Perforin
Produce pore in plasma membrane
Activation of the complement system causes
Opsonization
Chemotaxis
Lysis
Agglutination
How do viruses evade neutralizing antibodies
Produce large amounts of soluble protein to soak up antibody
Variation in viral antigens
Production of antibodies capable of neutralization
Slow production of antibodies
Antibody dependent cell mediated cytotoxicity
Antibodies bind to viral antigens expressed on surface of host cells, host cells are destroyed by phagocytosis or by complement mediated cytolysis
Virus Neutralization
Neutralizing antibodies prevent virus attachement and entry into host cells, bind viral capsid or host envelope
Viroceptors
Virus encoded proteins that are homologous to the receptor for cytokines, secreted cytokine receptor homolog bind to cytokines and serve as competitive antagonists
Autocrine
infected cell secretes the INF that acts on same cell triggering apoptosis
Opsonization
Coating of virions with antibodies, antibody coated virion is recognized and phagocytosed by macrophages and sometimes by neutrophils
How do type I interferons inhibit virus replication
- Activate latent ribonuclease - RNAase L
- RNAase L degrades viral RNA
- Synthesis of Mx proteins that bind and trap nucleocapsid and inhibit virus assembly
Adaptive Immunity
Antigen specific, responses take time to develop and is mediated by lymphocytes that possess surface receptors that are specific to each pathogen
Pattern Recognition Receptors
Surface receptors that recognize specific pathogen associated molecular patterns.
Mucocilliary Blanket
Layer of mucous produced by goblet cells that is kept in continuous flow by the coordinated beating of cilia on the luminal surface of the epithelial cells that line the nasal mucosa and airways
Antigen Multiplicity
Antigenic varients with little or no cross reactivity
Granzyme
Proteins that initiate apoptosis
At least three interferons have been identified, recently discovered. Expressed in response to viral infections and activation of toll-like receptors. Primary function as immuno regulator
Type III Interferon
Major classes of interferons based on antigenic and chemical differences
Type I
Type II
Type III
Roles of type I interferons
Inhibit virus replication
Activate NK cells
Increase expression of MHC-1
Stimulate differentiation of monocytes into dendritic cells
Maturation of dendritic cells
Memorty T cell proliferation
CD8+ Tc Cell mechanism of action
- Tc cell interaction with infected cell containing microbial antigen
- Killing of infected cell
Humoral immunity is mediated by
Antibodies released from B lymphocytes
Immunocomplex formation
Clumping of viruses, reduces the number of viral particles avilable for cell invasion
Cytoplasmic granules of NK cells contain
Perforin
Granzyme
