Chapter 15: Innate Immunity Flashcards
three types of physical barriers
epithelial, blood-brain, maternofetal (placental)
barrier that lines the mucosa of digestive, genitourinary, and respiratory tracts
epithelial barrier
epithelial barriers are held together by
tight junctions
multiprotein adhesion complexes, strictly regulated and control what passes through/keeps microbes out
tight junctions
barrier with highly selective permeability, blocks most molecules from entering the brain
blood-brain barrier
the blood-brain barrier is held together by ______ that only allow ___, ____, and ____ through
endothelial tight junctions; oxygen, carbon dioxide, alcohol
the blood-brain barrier keeps out all pathogens that may enter from
the blood
barrier that keeps the fetus pathogen-free and separates the fetal and maternal bloodstreams
maternofetal (placental) barrier
through the maternofetal barrier, the exchange of oxygen, carbon dioxide, nutrients, and waste are performed WITHOUT ____ and ____ blood mixing
fetal, maternal
molecules able to freely cross the blood-brain barrier
oxygen, carbon dioxide, alcohol
the immune system distinguishes ___ from ___
self, non-self
the immune system senses and reacts to
foreign antigens
difference between innate immunity and adaptive immunity
innate immunity is nonspecific, adaptive immunity is specific
system of nonspecific mechanisms that the body uses for protecting against pathogens, immediately activated
innate immunity
immune responses activated by a specific antigen, mediated by B and T cells, take a week or so to develop
adaptive immunity
formation of blood cellular components, how all immune cells are made (origin)
hematopoiesis
hematopoiesis starts at the
hematopoietic precursor stem cell (bone marrow)
white blood cells, can phagocytose and kill microbes
neutrophils
white blood cells, secrete antimicrobial compounds
eosinophils/basophils
white blood cells, differentiate into macrophages or dendritic cells
monocytes
white blood cells, only found in tissues, secrete antimicrobial compounds
mast cells
adaptive, B, T, natural killer cells
lymphocytes
monocytes circulate in the ____ and engulf foreign material (phagocytosis)
blood
monocytes enter ____ and differentiate to macrophages or dendritic cells
tissues
cells that are phagocytic and dispersed in tissues, likely to make first contact with invading pathogens
macrophages
macrophages __________ from engulfed pathogens to the adaptive immune system
present antigens
cells that phagocytose, process, and present small antigens on their surface
dendritic cells
dendritic cells are important to bridge _________ and _________
innate and adaptive immunity
process of engulfing foreign bacteria
phagocytosis
steps of phagocytosis
- bacterium binds to phagocytic cell surface
- phagocyte pseudopods extend and engulf the organism
- invagination of phagocyte membrane traps organism within a phagosome
- lysosome fuses and deposits enzymes into the phagosome (becomes a phagolysosome), enzymes then split macromolecules and generate reactive oxygen, destroying the organism
- results: either microbe is destroyed and microbial debris is released into extracellular space, or antigen is presented on the membrane
neutrophils, monocytes, macrophages, kill pathogens, important step in antigen presentation
phagocytes
activate the adaptive immune system
antigen-presenting cells (APCs)
immune cells that present antigen on their cell surface
dendritic cells
group of organs, vessels, and tissues that complement the immune and circulatory systems
lymphatic system
where immune cells originate and mature
primary organs
where immune cells encounter antigen
secondary organs
secondary organs
lymph nodes, lymphatic vessels
interstitial fluids and white blood cells from tissues, drained from tissues by lymphatic vessels
lymph
microbes that enter past the skin are targeted by
sebum
microbes that enter past the mucosa are targeted by
mucus
microbes that enter past the lungs are targeted by
stomach acid
chemical barrier that targets peptidoglycan
lysozyme
chemical barrier that produces superoxide radicals
lactoperoxidase
chemical barrier that are positively-charged small molecules and target membranes
defensins
five cardinal signs of inflammation
heat, edema, redness, pain, altered function/movement (HERPA)
infection/inflammation of the lungs, identified by light regions/cloudiness (bilateral inflammation) caused by mycobacterium tuberculosis
pneumonia
movement of white blood cells from the bloodstream into the tissues
extravasation
dominant cell infiltrating the tissues in extravasation
neutrophils
extravasation causes
the signs of inflammation (HERPA)
inflammatory response pathway
- resident macrophages engulf and digest invading organisms
- macrophages release inflammatory mediators that recruit more help (cytokines, vasoactive factors, chemokines)
- endothelial tight junctions loosen
- cytokines promote expression of adhesion molecules on endothelial cells
- allows for extravasation of WBCs expressing integrins that bind to endothelial adhesion molecules
- damaged tissue cells express bradykinin (directly promotes vasodilation), also activate mast cells
- bradykinin promote prostaglandin secretion from endothelial cells, signals to nerve cells to send a pain input to the brain
- once microbe is cleared, neutrophils, cytokines, and chemokines are removed and the tissue can heal
causes cell damage as a worthwhile cost to clear out the pathogen, damage done is repairable quickly
acute inflammation
occurs when the foreign body persists in the tissues, continues damaging and eventually causes permanent tissue damage, can be caused by nonliving irritants (splinters, etc.)
chronic inflammation
to evaluate if the cell they are contacting is self or non-self, macrophages probe their environment with
pseudopods
phagocytosis kills microbes by fusing the _____ with the ______
phagosome, lysosome
many microbes (especially viruses) not only survive phagocytosis, but use it to enter the
cell cytoplasm
packed with pro-inflammatory molecules, prevents wound healing, short-lived and die by apoptosis
neutrophils
programmed/controlled cell death
apoptosis
apoptosis is clean because it
maintains membrane integrity to limit the release of harmful neutrophil contents
apoptotic neutrophils are phagocytosed by macrophages and degraded, allowing for ______ to resolve and ________ to begin
inflammation; tissue repair
kill defective host cells (virus-infected, intracellular bacteria, cancer), not specific (only discern between self and non self enough)
natural killer (NK) cells
NK cells DO NOT directly kill microbes, they kill
cells that allow for microbial replication
self molecule receptor, expressed by all host cells
MHC I
NK cells know which cells to kill by looking for defective cells that express _________, NK cell will force cell to undergo apoptosis
less MHC I
NK cells kill by inserting ________ and entering target host cell membranes that lack _______
perforin (pore-forming protein); MHC I
NK cells release cytotoxic proteins like _______ that enter through the perforin pores and initiate apoptosis
granzyme
cells die when they are supposed to (programmed), NK cells kill defective cells
apoptosis
cells die when they are not supposed to
cell lysis
how innate cells sense if there are microbial invaders, recognize conserved molecular patterns that are common to broad classes of microbes
pathogen-associated molecular patterns (PAMPs)
patterns that cells might leak out when damaged
damage-associated molecular patterns (DAMPs)
immune cells use ________ to sense PAMPs and DAMPs and initiate the appropriate response
pattern-recognition receptors (PRRs)
primary example of pattern recognition receptors (PRRs)
Toll-Like Receptor family
PRR activation leads to the cell producing _______ that alert neighboring cells and immune cells the type of ______ taking place
cytokines; infection
pathogens sensed by TLRs on the cell membrane
PAMPs in extracellular environment (bacteria, yeast, protists, etc.)
pathogens sensed by TLRs on endosomal membranes
PAMPs taken up by endocytosis related to viruses and intracellular bacteria
cytokines that cells express during infection to warn other cells to establish an antiviral state
interferons
systemic inflammatory response to infection that can lead to multi-organ failure and death
sepsis
main driver of sepsis
bacterial infection infiltrates the bloodstream and is sensed by TLRs on monocytes and platelets
any molecule that can cause fever
pyrogens
pyrogens cause fever by
influencing the hypothalamus to increase body heat (fever creates an environment inhospitable to bacterial growth)
family of proteins present in the blood that react to bacterial membranes
complement
consequences of complement
can coat the bacterial cell and make them easier to be eaten by phagocytes (opsonization); add up to form membrane attack complex that forms pores in the membrane
all of our own cells have _______ proteins that inactivate complement, bacteria do not have these proteins
surface