Ch2pp43-52

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Questions and Answers

Which cells secrete type I IFNs in response to recognition of viral nucleic acids by TLRs, RLRs, and other pattern recognition receptors?

Macrophages

B lymphocytes

Plasmacytoid dendritic cells (correct)

Natural killer cells

What is the basis for the use of IFN-α to treat some forms of chronic viral hepatitis?

Enhancement of viral entry into host cells

Inhibition of viral replication and destruction of viral genomes (correct)

Stimulation of inflammatory response

Induction of fever for virus clearance

What is associated with severe cases of COVID-19?

Overproduction of type I IFNs

Reduced inflammatory response

Enhanced activation of NK cells

Inherited or acquired deficiency of type I IFN production or signaling (correct)

What enhances the ability of NK cells to kill infected cells?

Type I IFNs Signup and view all the answers

Which cells secrete cytokines that induce inflammation?

Innate lymphoid cells (ILCs) Signup and view all the answers

What activates macrophages to kill phagocytosed microbes?

Cytokine interferon-γ (IFN- γ) Signup and view all the answers

What do complement proteins do when activated in innate immunity?

Coat (opsonize) microbes for phagocytosis, stimulate inflammation, and lyse microbes Signup and view all the answers

What is the function of type I interferons in antiviral defense?

Inhibit viral replication Signup and view all the answers

What do phagocytes do in inflammation?

Recruited from the circulation to sites of infection and tissue damage, ingest and destroy microbes and damaged cells Signup and view all the answers

What ensures that adaptive immunity is elicited by microbes and not by nonmicrobial substances?

Requirement for second signals that work together with antigens to activate B and T lymphocytes Signup and view all the answers

What is the role of natural killer (NK) cells in antiviral defense?

Kill host cells infected by intracellular microbes and produce the cytokine interferon-γ (IFN- γ) Signup and view all the answers

What is the role of cytokines in innate immunity?

Stimulate inflammation, activate NK cells, activate macrophages, and prevent viral infections Signup and view all the answers

What is the name of the first signal required for full activation of antigen-specific lymphocytes?

Signal 1 Signup and view all the answers

Why does the requirement for microbe-dependent second signals exist?

To ensure lymphocytes respond to infectious pathogens and not harmless substances Signup and view all the answers

What may induce adaptive immune responses without microbes?

Adjuvants that elicit innate immune reactions Signup and view all the answers

What are the second signals for T cells called?

Costimulators Signup and view all the answers

How do blood-borne microbes activate the complement system?

Through the alternative pathway Signup and view all the answers

What is the role of second signals in relation to adaptive immunity?

They stimulate adaptive immunity and guide the nature of the adaptive immune response Signup and view all the answers

What constitutes innate immunity in multicellular organisms?

Intrinsic mechanisms of defense against infections Signup and view all the answers

What are Toll-like receptors (TLRs) a major class of?

Innate immune system receptors that recognize different microbial products. Signup and view all the answers

What do inflammasomes generate?

The active form of the proinflammatory cytokine interleukin-1β (IL-1β) Signup and view all the answers

Which components are principal components of innate immunity?

Epithelial barrier cells, phagocytes, dendritic cells, mast cells, natural killer cells, cytokines, and plasma proteins. Signup and view all the answers

What do epithelia provide as a defense against microbes?

Physical barriers against microbes, produce antimicrobial peptides, and contain lymphocytes. Signup and view all the answers

Which mechanism prevents excessive tissue damage in innate immune responses?

Production of anti-inflammatory cytokines like IL-10 and IL-1 receptor antagonist Signup and view all the answers

What is the role of type I interferons (IFN-α, IFN-β) in response to viral infections?

Interfering with viral replication and increasing susceptibility to CTL-mediated killing Signup and view all the answers

What do pathogens do to evade innate immunity?

Resistance to phagocytosis, reactive oxygen intermediates, complement activation, and antimicrobial peptides Signup and view all the answers

What is the function of innate immune responses besides combating infections?

Serving as a warning function, alerting the adaptive immune system of the need for an effective immune response Signup and view all the answers

How is inflammasome activation controlled?

Tightly controlled by posttranslational modifications and micro-RNAs Signup and view all the answers

How do intracellular bacteria like Listeria monocytogenes evade innate immunity?

Produce proteins enabling escape from phagocytic vesicles Signup and view all the answers

What is the role of feedback mechanisms in innate immune responses?

Induce expression of inhibitors of cytokine signaling in response to TLR signaling Signup and view all the answers

What do some intracellular bacteria like mycobacteria contain that inhibits fusion of phagosomes with lysosomes?

Lipids inhibiting fusion of phagosomes with lysosomes Signup and view all the answers

What is the effect of microbial evasion on innate immunity?

Microbes have evolved mechanisms to evade innate immunity including resistance to various components like phagocytosis and antimicrobial peptides. Signup and view all the answers

What do feedback mechanisms induce in response to TLR signaling?

Expression of inhibitors of cytokine signaling such as suppressors Signup and view all the answers

Study Notes

Innate Immune Responses and Microbial Evasion

Viral DNA recognition by CDSs induces autophagy, leading to the destruction of viral-containing organelles by lysosomes.
Innate response to viral infections involves increased apoptosis of infected cells, aiding in the elimination of infection reservoirs.
Innate immune responses are regulated by mechanisms preventing excessive tissue damage, including the production of anti-inflammatory cytokines like IL-10 and IL-1 receptor antagonist.
Feedback mechanisms induce expression of inhibitors of cytokine signaling, such as suppressors of cytokine signaling (SOCS) in response to TLR signaling.
Inflammasome activation is tightly controlled by posttranslational modifications and micro-RNAs.
Type I interferons (IFN-α, IFN-β) are produced in response to TLR signaling and other viral nucleic acid sensors, interfering with viral replication and increasing susceptibility to CTL-mediated killing.
Microbes have evolved mechanisms to evade innate immunity, including resistance to phagocytosis, reactive oxygen intermediates, complement activation, and antimicrobial peptides.
Pathogenic microbes have evolved to resist innate immunity, with some intracellular bacteria and viruses encoding proteins that block induction of type I IFNs.
Some intracellular bacteria, like Listeria monocytogenes, produce proteins enabling escape from phagocytic vesicles, while mycobacteria contain lipids inhibiting fusion of phagosomes with lysosomes.
Innate immune responses not only combat infections but also serve as a warning function, alerting the adaptive immune system of the need for an effective immune response.
Innate immune responses generate molecules that provide signals, in addition to antigens, required to activate naive T and B lymphocytes.
The innate immune response to microbes stimulates adaptive immune responses, contributing to a comprehensive immune defense against infections.

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Test your knowledge of the two signals required for full activation of antigen-specific lymphocytes and the concept of danger signals in the adaptive immune system.