Chapter 15: Innate Immunity Flashcards by Ella Ford

three types of physical barriers

epithelial, blood-brain, maternofetal (placental)

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barrier that lines the mucosa of digestive, genitourinary, and respiratory tracts

epithelial barrier

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epithelial barriers are held together by

tight junctions

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multiprotein adhesion complexes, strictly regulated and control what passes through/keeps microbes out

tight junctions

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barrier with highly selective permeability, blocks most molecules from entering the brain

blood-brain barrier

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the blood-brain barrier is held together by ______ that only allow ___, ____, and ____ through

endothelial tight junctions; oxygen, carbon dioxide, alcohol

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the blood-brain barrier keeps out all pathogens that may enter from

the blood

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barrier that keeps the fetus pathogen-free and separates the fetal and maternal bloodstreams

maternofetal (placental) barrier

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through the maternofetal barrier, the exchange of oxygen, carbon dioxide, nutrients, and waste are performed WITHOUT ____ and ____ blood mixing

fetal, maternal

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molecules able to freely cross the blood-brain barrier

oxygen, carbon dioxide, alcohol

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the immune system distinguishes ___ from ___

self, non-self

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the immune system senses and reacts to

foreign antigens

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difference between innate immunity and adaptive immunity

innate immunity is nonspecific, adaptive immunity is specific

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system of nonspecific mechanisms that the body uses for protecting against pathogens, immediately activated

innate immunity

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immune responses activated by a specific antigen, mediated by B and T cells, take a week or so to develop

adaptive immunity

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formation of blood cellular components, how all immune cells are made (origin)

hematopoiesis

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hematopoiesis starts at the

hematopoietic precursor stem cell (bone marrow)

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white blood cells, can phagocytose and kill microbes

neutrophils

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white blood cells, secrete antimicrobial compounds

eosinophils/basophils

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white blood cells, differentiate into macrophages or dendritic cells

monocytes

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white blood cells, only found in tissues, secrete antimicrobial compounds

mast cells

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adaptive, B, T, natural killer cells

lymphocytes

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monocytes circulate in the ____ and engulf foreign material (phagocytosis)

blood

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monocytes enter ____ and differentiate to macrophages or dendritic cells

tissues

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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

1. bacterium binds to phagocytic cell surface 2. phagocyte pseudopods extend and engulf the organism 3. invagination of phagocyte membrane traps organism within a phagosome 4. lysosome fuses and deposits enzymes into the phagosome (becomes a phagolysosome), enzymes then split macromolecules and generate reactive oxygen, destroying the organism 5. 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

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

1. resident macrophages engulf and digest invading organisms 2. macrophages release inflammatory mediators that recruit more help (cytokines, vasoactive factors, chemokines) 3. endothelial tight junctions loosen 4. cytokines promote expression of adhesion molecules on endothelial cells 5. allows for extravasation of WBCs expressing integrins that bind to endothelial adhesion molecules 6. damaged tissue cells express bradykinin (directly promotes vasodilation), also activate mast cells 7. bradykinin promote prostaglandin secretion from endothelial cells, signals to nerve cells to send a pain input to the brain 8. 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