2.2 Flashcards
specificity
innate immunity
for structures shared by classes of microbes (pathogen-associated molecular patterns) or damaged cells (damaged-asssociaed molecular patterns)
specificity
adaptive immunity
for structural detail of microbial molecules (antigens) may recognize nonmicrobial antigens
receptors
innate
encoded in germline; limited diversity (pattern recognition receptors)
receptors
adaptive
encoded by genes produced by somatic recombination of gene segments; greater diversity
distribution of receptors
innate
noncolonal: identical receptors on all cells of the same lineage
distribution of receptors
adaptive
colonal: clones of lymphocytes with distinct specificities express different receptors
discrimination of normal self and nonself
innate
yes; healthy host cells are not recognized, or they may express molecules that prevent innate immune reactions
discrimination of normal self and nonself
adaptive
yes; based on selection against self-reactive lymphocytes; may be imperfect (giving rise to autoimmunity)
The two principal types of reaction of the innate immune
system are:
- Stimulate acute Inflammation.
- - Anti-viral defenses
- Stimulate acute Inflammation.
— which is the accumulation of leukocytes,
phagocytic cells, plasma proteins, and
fluid derived from the blood at an
extravascular tissue site of infection or injury.
Anti-viral defenses mediated by: (2)
— NK cell-mediated killing of virus-infected cells.
— Interferon α/β (Type I interferons), which are
secreted by virus-infected cells, bind to
receptors on surrounding cells, and induce
an anti-viral state in those cells.
Prominent cell-associated Pattern Recognition Receptors and
Sensors of Innate Immunity (3)
Toll-Like Receptors (TLRs).
NOD-like Receptors (NLRs).
RIG-like Receptors (RLRs)
NOD-like Receptors (NLRs).
– NLRs are a family of more than 20 different cytosolic proteins that recognize
PAMPs and DAMPs in the cytoplasm and recruit other proteins to form signaling
complexes (such as inflammasomes) that promote inflammation.
RIG-like Receptors (RLRs).
– RLRs are cytosolic sensors of viral RNA that respond to viral nucleic acids
by inducing production of the antiviral type I interferons.
Components of the Innate Immune Response.
- Epithelial barriers (3)
physical barrier to infection
killing of microbes by locally produced antibiotics
killing of microbes and infected cells by intraepithelial lymphocytes
Components of the Innate Immune Response.
- Phagocytes (2)
neutrophils
monocytes/macrophages
.Neutrophils. (3)
…Circulating phagocytic cells; Most abundant leukocytes blood.
…First cell type to respond to most infections.
…Live only a few hours in tissues.
.Monocytes/Macrophages. (1)
…Blood monocytes differentiate into tissue macrophages
after entering tissues.
Macrophages: fxn (2)
Secrete cytokines that induce
inflammation, and ingest and
destroy microbes.
Macrophages:
life span
Survive for long time periods in
tissues
Components of the Innate Immune Response.
- Dendritic cells (sentinel cells) (2)
…Secrete cytokines.
…Present antigenic peptides to T cells.
Components of the Innate Immune Response. mast cells (4)
…Abundant cytoplasmic granules.
…Present in skin and mucosal epithelium.
…contain vasoactive amines (e.g. histamine).
…cause vasodilation and capillary permeability
Components of the Innate Immune Response.
Innate lymphoid cells (2)
…lymphocyte-like cells.
…produce cytokines but lack T cells antigen receptors (TCRs)
Components of the Innate Immune Response.
- Complement (1)
…Induce inflammation, opsonize microbes enhancing
their phagocytosis, cause osmotic lysis of microbes.
Delivery of neutrophils, macrophages, T
lymphocytes, complement proteins, antibodies,
and acute-phase reactants to the site of
inflammation is due to reversible changes in
blood vessels in the infected or damaged tissue: (3)
– increased blood flow into tissue due to
arteriolar dilation
– increased adhesiveness of circulating
leukocytes to the endothelial lining of venules
– increased permeability of capillaries and
venules to plasma proteins and fluid
All these changes are induced by cytokines and
small molecule mediator initially derived from
(2) in response
to stimulation of pathogen-associated molecular
patterns (PAMPs) or damage-associated
molecular patterns (DAMPs).
sentinel cells (resident phagocytic cells) in the tissue, as well as endothelial cells,
Sequence of events in migration of blood leukocytes to sites of infection (4)
The sequence of selectin-mediated rolling, chemokine-dependent integrin-mediated
firm adhesion, and chemokine-mediated motility leads to the migration of blood
leukocytes to the extravascular site of infection.
Components of the Innate Immune Response.
- Natural Killer (NK) cells (2)
…Kill virus-infected cells.
…Secrete interferon γ which activates macrophages.
inhibitory receptor engaged
NK cell not activated, no cell killing
inhibitory receptor not engaged
NK cell activated; killing of infected cell
Components of the Innate Immune Response.
- IFN α/β (Type I Interferons) (1)
…Secreted by virus infected cells, induce anti-viral state in
surrounding cells.
The major protective innate immune responses to different microbes are:
Extracellular bacteria and fungi
are combated mainly by an acute inflammatory
response, in which neutrophils and monocytes are recruited to the site of
infection, and by the complement system.
The major protective innate immune responses to different microbes are:
Intracellular bacteria,
which can survive inside phagocytes, are eliminated when
the microbial killing functions of phagocytes are activated by Toll-like receptors
and other sensors, as well as by cytokines.
The major protective innate immune responses to different microbes are:
viruses
Defense against viruses is provided by type I interferons (interferons α and β) and
by natural killer (NK) cells.
