Chapter 4 Flashcards
What are the cellular components of the innate immune system?
epithelial barriers, leukocytes (neutrophils, macrophages, NK cells, lymphocytes with invariant antigen receptors, and
mast cells
how does the immune system recognize PAMPs?
uses cell-associated
pattern recognition receptors, present on plasma
and endosomal membranes and in the cytoplasm
what are PAMPs?
shared by
microbes, are not present on mammalian cells, and
are often essential for survival of the microbes,
thus limiting the capacity of microbes to evade
detection by mutating or losing expression of these
molecules
What are DAMPs?
molecules made by the host but whose expression
or location indicates cellular damage
What are examples of cytoplasmic pattern recognition receptors?
RIG-like receptors (RLRs), which recognize viral
RNA, and the NOD-like receptors (NLRs), which
recognize bacterial cell wall constituents and also
sense sodium urate and other crystals
What do TLRs and RLRs activate?
the transcription factors
NF-κB and AP-1, which promote inflammatory
gene expression, and the IRF transcription factors
that promote expression of the antiviral type I
interferon genes
What is an inflammasome?
specialized
complex that forms in response to PAMPs and
DAMPs, is composed of a NOD-like receptor, an
adaptor, and the enzyme caspase-1, the main
function of which is to produce active forms of the
inflammatory cytokines IL-1 and IL-18
What do soluble pattern recognition and effector molecules do?
bind microbial ligands and
enhance clearance by complement-dependent and
complement-independent mechanisms
What are NK cells?
lymphocytes that defend against
intracellular microbes by killing infected cells and
providing a source of the macrophage-activating
cytokine IFN-γ
what regulates activation of NK cells?
a combination of activating
and inhibitory receptors. Inhibitory receptors recognize class I MHC molecules, because of which
NK cells do not kill normal host cells but do kill
cells in which class I MHC expression is reduced,
such as virus-infected cells
What is included in the complement system?
several plasma
proteins that become activated in sequence by
proteolytic cleavage to generate fragments of the
C3 and C5 proteins, which promote inflammation,
or opsonize and promote phagocytosis of microbes.
Complement activation also generates membrane
pores that kill some types of bacteria
how is the complement system activated?
on microbial surfaces
and not on normal host cells because microbes
lack regulatory proteins that inhibit complement.
In innate immune responses, complement is
activated mainly spontaneously on microbial
cell surfaces and by mannose-binding lectin to
initiate the alternative and lectin pathways,
respectively
what are the two major effector functions of innate immunity?
induce inflammation, which involves
the delivery of microbe-killing leukocytes and
soluble effector molecules from blood into tissues,
and to block viral infection of cells by the antiviral
actions of type 1 interferons
what induces the two major effector functions of innate immunity?
PAMPs and DAMPs,
which initiate signaling pathways in tissue cells
and leukocytes that activate transcription factors
and lead to the expression of cytokines and other
inflammatory mediators
What do TNF and Il-1 do?
activate endothelial cells, stimulate chemokine
production, and increase neutrophil production by
the bone marrow. IL-1 and TNF both induce IL-6
production
