The Immune System Flashcards
the innate defense system is ______
nonspecific
the innate defense system
is always ________
responding within _______
to protect the body from ________
prepared
minutes
foreign substances
the innate defense system has two barricades
the first line of defense
the second line of defense
the first line of defense
consists of surface barriers
intact skin and mucosae.
the second line of defense called into action whenever the first line has been ________
penetrated
the second line of defense relies on ____ defenses such as ______ proteins, ______, and other cells to inhibit the invaders’ spread throughout the body.
internal
antimicrobial
phagocytes
The hallmark of the second line
of defense is
inflammation
the adaptive defense system is _______
specific
the adaptive defense system attacks _____ foreign substances
identified
The adaptive defense response, which provides the body’s _________, takes considerably ______ to mount than the innate defense response.
third line of defense
longer
immune system is a _____ system rather than an ____ system in an anatomical sense.
functional
organ
The innate and adaptive systems release and recognize (bind to) many of the
same defensive molecules
The innate responses are not as nonspecific as once thought. Indeed, they have __________
specific pathways to target certain foreign substances.
Proteins released during innate responses alert cells of the _____ to the presence of specific foreign molecules in the body
adaptive system
When the immune system is operating effectively, it protects the body from most infectious microorganisms, cancer cells, and (unfortunately) transplanted organs and grafts. It does this both directly, by ______, and indirectly, by ________-and __________.
cell attack
releasing mobilizing chemicals
protective antibody molecules
pathogens
harmful or disease-causing microorganisms
we come fully equipped with _____ defense
innate
the innate defenses ____ the workload of the adaptive system by ____ the entry and ____ of microorganisms in the body.
reduces
preventing
spread
The body’s first line of defense the ___ and the _______, along with the _____ these membranes produce-is highly effective.
skin
mucous membranes
secretions
As long as the epidermis is unbroken, this heavily ___________ membrane is a formidable _____ barrier to most microorganisms
keratinized epithelial
physical
Keratin is also resistant to most _____ and ____ and to _____ and _____.
weak acids
bases
bacterial enzymes
toxins
Recall that mucous membranes line all body
cavities that ___________
open to the exterior
examples of mucous membranes
the digestive, respiratory, urinary, and reproductive tracts.
skin and mucous membranes produce a variety of protective chemicals
acid enzymes mucin defensins other chemicals
acid
The acidity of skin, vaginal, and stomach secretions _____________
the acid mantle inhibits bacterial growth
Enzymes
_______ found in saliva, respiratory mucus,
and ____fluid of the eye destroys bacteria. ___________ in the stomach kill many different microorganisms
lysozyme
lacrimal
Protein digesting enzymes
______ dissolved in water forms thick, sticky mucus
that lines the ______ and _______ passageways. This mucus traps many microorganisms. Likewise, the mucin in _______ traps microorganisms and washes them out of the mouth into the stomach where they are digested.
mucin
digestive
respiratory
watery saliva
Mucous membranes and skin secrete small
amounts of broad-spectrum antimicrobial peptides
called _____. Defensin output increases dramatically
in response to _____ when surface barriers are
breached. Using various mechanisms, such as disruption of microbial membranes, defensins help to control ____ and ____ colonization in the exposed areas.
defensins
inflammation
bacterial
fungal
In the skin, some lipids in _____ and
______ in eccrine sweat are ____ to bacteria.
sebum
dermcidin
toxic
These protective tactics identify potentially harmful substances by recognizing (binding to) molecules with specific shapes that are part of infectious organisms (bacteria, viruses, fungi, and various parasites) but
not normal human cells. The receptors that do this are called
pattern recognition receptors
one class of pattern recognition receptors called ___________ plays a central role in triggering an immune response
Toll-like receptors (TLRs)
There are ___ types of human TLRs, each recognizing a particular class of ________
11
attacking microbe
give examples of some TLRs
one type responds to a glycolipid in cell walls of the tuberculosis bacterium
another type responds to a component of gram-negative bacteria such as salmonella
These pattern recognition receptors allow the cells to recognize invaders and sound a
chemical “alarm” that initiates inflammation
Pathogens that get through the skin or mucosae into the underlying connective tissue are confronted by
phagocytes
Neutrophils, the most abundant type of _____ cell, become _____ on encountering _____ material in the tissues
White blood
phagocytic
infectious
the most voracious phagocytes are
macrophages
Macrophages derive from white blood
cells called
monocytes
what are the 2 types of macrophages
free and fixed macrophages
Free Macrophages
wander throughout the tissue spaces in
search of cellular debris or “foreign invaders.”
Fixed Macrophages
such as stellate macrophages in the
liver, are permanent residents of particular organs.
In phagocytosis
The particle (pathogen) is pulled inside,
enclosed within a membrane-lined vesicle called _____
phagosome
The resulting phagosome then fuses with a lysosome to form a
phagolysosome
Neutrophils and macrophages generally kill ingested prey by _____ the phagolysosome and digesting its contents with ______ enzymes.
acidifying
lysosomal
some pathogens such as the tuberculosis bacillus and certain parasites are resistant to_____ enzymes and can even multiply wthin the _____-.
lysosomal
phagolysosome
in cases like tuberculosis bacillus other immune cells called ________ release chemicals that stimulate the macrophage
helper T cells
when helper T cells release chemicals that stimulate macrophages This activates additional enzymes that produce a lethal
respiratory burst
The respiratory burst promotes killing of pathogens by:
- Liberating a deluge of highly destructive free radicals
- Producing oxidizing chemicals (hydrogen peroxide and a substance identical to household bleach)
- Increasing the phagolysosome’s pH and osmolarity, which activates other protein-digesting enzymes that digest the invader
Neutrophils also pierce the pathogen’s membrane by using
defensins
Phagocytic attempts are not always successful. In order for a phagocyte to ingest a pathogen, the phagocyte must first ____ to that pathogen, a feat made possible by recognizing the pathogen’s carbohydrate “______.”
adhere
signature
complement proteins or antibodies
opsonins
Any pathogen can be coated with
opsonins, a process called
opsonization
what does opsonization do
greatly accelerates phagocytosis of that pathogen.
When phagocytes are unable to ingest their targets (because of size, for example), they can
release their toxic chernicals into
the extracellular fluid.
Whether killing ingested or extracellular
targets, ______ rapidly destroy themselves in the process. In contrast, _____ are more robust and can survive to kill another day.
neutrophils
macrophages
Natural killer (NK) cells, which “police” the body in ____and ____, are a unique group of defensive cells that can kill ____ cells and _____body cells ____ the adaptive immune system is activated.
blood lymph cancer virus infected before
NK cells are part of a small group
of
large granular Lymphocytes.
Unlike lymphocytes of the adaptive immune system, which only recognize and react against specific infected or tumor cells, NK cells are
far less picky
NKs can eliminate a variety of infected or cancerous cells by detecting general abnormalities such as the lack of “self” cell-surface proteins called
MHC
The name “natural” killer cells reflects their
nonspecificity
NK cells are not
phagocytic
how do NK cells kill
directly contacting the target cell, inducing it to undergo apoptosis (programmed cell death).
NK cells kill by the same method as
used by cytotoxic T cells
NK cells also secrete ____ chemicals
that enhance the _______
potent
inflammatory response
what is inflammation
nonspecific response to any tissue injury
what are some causes of inflammation
physical trauma
intense heat
irritating chemicals
infection
Inflammation has several beneficial effects
- It prevents the spread of damaging agents to nearby tissues.
- It disposes of cell debris and pathogens.
- It alerts the adaptive immune system.
- It sets the stage for repair
How can you tell if inflammation is present
There are four cardinal signs of acute short term inflammation
redness, heat, swelling, pain
(impaired function some authorities consider it)
The inflammatory process begins with a chemical “alarm”
a flood of inflammatory chemicals released into the extracellular fluid.
Inflammatory chemicals are released by
injured or stressed tissue cells, and immune cells.
what do mast cells release
histamine
Other inflammatory chemicals include
kinins, prostaglandins, cytokines
cytokines
a group of chemical mediators of immune responses
If pathogens provoked the inflammation, a
group of plasma proteins known as ______ is activated to form potent inflammatory chemicals
complement
All inflammatory chemicals ____ local arterioles and
make local capillaries ____.
Many also attract _____ to the injured area.
In addition, some have individual inflammatory roles,
such as _________ and other elements of _______ immunity
dilate leakier phagocytes mobilizing lymphocytes adaptive
Vasodilation of local arterioles causes local
hyperemia (increased blood flow)
Hyperemia brings more ____ and _____ of the immune system to the injured area.
cells
chemicals
hyperemia accounts for which cardinal signs
redness and heat of an inflamed region
Inflammatory chemicals also increase the permeability of
local capillaries and venules
Consequently, _______ fluid containing clotting factors and antibodies-seeps from the blood into the tissue spaces.
exudate
This influx of protein-rich fluids into the tissue spaces
sweeps foreign material into the ____________ so it can be processed in the________
lymphatic vessels
lymphatic nodes
the influx of proteins also delivers important proteins such as ____and ____ factors to the interstitial fluid
complement
clotting
The clotting factors form a gel-like fibrin ___
that acts as a scaffold for_____
mesh
permanent repair
The mesh also _____ the injured area and
prevents bacteria and other harmful agents
from ____
isolates
spreading
The increased tissue fluid causes the _____________
that presses on adjacent nerve endings, contributing to a sensation of ____.
local swelling edema
pain
Pain also results from the release of ___________ and the sensitizing effects of released _______
and _____.
bacterial toxins
prostaglandins
kinins
Aspirin and some other anti inflammatory drugs reduce pain by ______________________________
inhibiting prostaglandin synthesis
Soon after inflammation begins, ______
flood the damaged area. ______ lead followed by _____
phagocytes
neutrophils
macrophages
Phagocyte Mobilization
leukocytosis
Margination
Diapedesis
chemotaxis
Injured cells release chemicals called
leukocytosis inducing factors
Leukocytosis. Injured cells release chemicals called
___________
In response, ______ enter blood from red bone marrow and within a few hours, the number of neutrophils in blood increases four- to five fold.
This leukocytosis, the increase in __________, is characteristic of inflammation
neutrophils
leukocytosis-inducing factors.
white blood cells
Margination
refers to the phenomenon of phagocytes clinging to the inner walls (margins) of the capillaries and post capillary venules.
Inflamed endothelial cells sprout ______ that signal “________.”
cell adhesion molecules
this is the place
As neutrophils encounter these CAMs, they
bind breifly
As neutrophils encounter these CAMs, they bind briefly. This causes them to
slow and roll along the inner surface of the blood vessel so they can be activated by inflammatory chemicals.
Once activated, neutrophils sprout additional
CAMs on their own plasma membranes
Once activated, neutrophils sprout additional CAMs on their own plasma membranes. This allows the neutrophils to
bind endothelial cells tightly, creating an initial foothold.
what is diapedesis
Continued chemical signaling prompts the neutrophils to flatten and squeeze between the endothelial cells of the capillary walls
Inflammatory chemicals act as homing devices,
or more precisely
chemotactic agents
_____ and other _____ migrate up the gradient of chemotactic agents to the site of injury
neutrophils
WBC
Within an hour after the inflammatory response has begun, _____ have collected at the site and are devouring any foreign material present
neutrophils
As the body’s counterattack continues, _____ follow ______ into the injured area.
monocytes
neutrophils
Monocytes are fairly poor _____, but within 12 hours of leaving the blood and entering the tissues, they ____ and develop large numbers of ____, becoming ____ with insatiable ____.
phagocytes swell lysosomes macrophages appetite
are the central actors in the final disposal of cell
debris as acute inflammation subsides, and they predominate at
sites of chronic inflammation.
macrophages
The ultimate goal of an inflammatory response is to clear the injured area of
pathogens, dead tissue
cells, and any other debris so that tissue can be repaired
what is pus
a mixture of dead or dying neutrophils, broken-down tissue cells, and living and dead pathogens
If the inflammatory
mechanism fails to clear the area of debris, collagen fibers may be laid down, which walls off the sac of pus, forming an
abscess
abscess may need to be _______ before healing
can occur.
surgically drained
Some bacteria, such as tuberculosis bacilli, resist digestion
by the macrophages that engulf them. They escape the effects
of prescription antibiotics by rernaining snugly enclosed within
their macrophage hosts. In such cases _______ form
granulomas
what do granulomas contain
tumorlike growths contain a central region of infected macrophages surrounded by uninfected macrophages and an outer fibrous capsule
A person may harbor pathogens walled off in granulomas
for years without displaying any symptoms. However, if the
person’s resistance to infection is ever compromised, the
bacteria may be activated and break free, leading to clinical disease symptoms.
antimicrobial proteins
enhance our innate defenses by attacking microorganisms directly or by hindering their ability to reproduce
The most important antimicrobial proteins are
interferons and complement proteins
Infected cells can do little to save themselves, but some
can secrete small proteins called
interferons
what do interferons do
help protect cells that have not yet been infected.
interferons diffuse to nearby cells, which they stimulate to synthesize proteins that block further protein synthesis and degrade _____. In this way they interfere with ________
viral RNA
viral replication
Because IFN protection is virus-specific, IFNs produced against a particular virus protect against
other viruses too
The IFNs are a family of __________ proteins produced by a variety of body cells, each having a slightly different _________ effect
modulating proteins
physiological
IFN alpha and beta have the
antiviral effects
activate NK cells
IFN gamma is also called
immune interferon
IFN gamma is secreted by ______
also explain its effect
lymphocytes and has widespread immune mobilizing effects, such as activating macrophages
Because both macrophages and NK cells can also act directly against cancerous cells, the ______ have an indirect role in fighting cancer.
interferons
IFNs are used to treat several disorders including
hepatitis C, genital warts, and multiple sclerosis
The term complement system, or simply complement, refers to a
group of at least 20 plasma proteins that normally circulate in the blood in an inactive state
the complement plasma proteins include those
numbered C1 through C9 plus several others that act as regulatory proteins and other factors
Complement provides a major mechanism for
destroying foreign substances in the body
complement activation does what
unleashes inflammatory chemicals that amplify virtually all aspects of the inflammatory process
Activated complement also lyses and kills
certain bacteria and other cell types
Although complement is a ____ defensive mechanism, it “complements” (enhances) the effectiveness of_____________
nonspecific
both innate and adaptive defenses
the three pathways by which complement can be activated.
classical
lectin
alternative
the classical pathway involves
antibodies
what are antibodies
water-soluble protein molecules that the adaptive immune system produces to fight off foreign invaders.
When antibodies bind to _____,
they can also bind complement components
pathogens
When antibodies bind to pathogens, they can also bind complement components. This double binding is the
first step in this classical complement activation pathway
The lectin patln vay involves
lectins
what are lectins
water-soluble protein molecules that the innate immune system produces to recognize foreign invaders
When lectins bind specific _____________, they can then bind and
activate complement.
sugars on the surface of microorganisms
The alternative pathway is triggered when spontaneously activated ____________ interact on the surface of microorganisms
C3 and other complement factors
These microorganisms lack the __________ inhibitors our own cells have
complement activation
The three pathways converge at C3, which is split into
C3a and C3b.
Splitting C3 initiates a
common terminal pathway that enhances inflammation, promotes phagocytosis, and can cause cell lysis
Cell lysis begins when ___ binds to the target cell ‘s surface and triggers the insertion of a group of complement proteins called _______ into the cell’s membrane.
C3b
MAC (membrane attack complex)
MAC forms and stabilizes a hole in the membrane that
allows a
massive influx of water, lysing the target cell.
The C3b molecules also act as
opsonins
C3a and
other molecules formed during complement activation amplify
the inflammatory response by
stimulating mast cells and basophils to release histamine and by attracting neutrophils and
other inflammatory cells to the area.
what is fever
an abnonnally high body temperature,
is a systemic response to invading microorganisms
When leukocytes and macrophages are exposed to foreign
substances in the body, they release chemicals called
pyrogens
These ______ act on the body’s thermostat cluster of neurons in the ______ raising the body’s
temperature above normal
pyrogens
hypothalamus
Fever causes the liver and spleen to
sequester iron and zinc, which may make them Jess available to support bacterial growth
fever increase the _________ of tissue cells, and may speed up ___________
metabolic rate
repair processes
adaptive immune system
the body’s built-in specific defensive system that stalks
and eliminates with nearly equal precision almost any type of pathogen that intrudes into the body
When it operates effectively, the adaptive immune system protects us from a wide variety of infectious agents, as well as from abnormal body cells. When it fails, or is disabled, devastating diseases such as
cancer and AIDS results
The activity of the adaptive immune system tremendously amplifies the _________ and is s responsible for most ________
inflammatory response
complement activation
the adaptive system must “meet” or be primed
by an initial exposure to a
specific foreign substance (antigen).
list the three characteristics of adaptive immunity
● It is specific. It recognizes and targets particular pathogens or foreign substances that initiate the immune response.
● It is systemic. Immunity is not restricted to the initial infection site.
● It has “memory.” After an initial exposure, it recognizes and mounts even stronger attacks on previously encountered pathogens.
that injecting antibody-containing serum did
not always protect the recipient from diseases the serum donor
had survived. In such cases, however, injecting the donor’s lymphocytes
did provide immunity
humoral immunity is also called
antibody mediated immunity
humoral immunity is provided by
antibodies present in the
body’s “humors,” or fluids (blood, lymph, etc.).
Though they are produced by lymphocytes, antibodies circulate freely in the ____ and ____, where they bind primarily to ______ bacteria, bacterial toxins, and free viruses inactivating them temporarily and marking them for destruction by _____ or ________.
blood lymph extracellular targets phagocytes complement
When lymphocytes themselves rather than antibodies defend
the body, the immunity is called
cellular or cell-mediated immunity because living cells provide the protection
cellular or cell-mediated immunity because living cells provide the protection
virus-infected or parasite-infected tissue
cells, cancer cells, and cells of foreign grafts
The lymphocytes act against such targets either directly, by ________, or
indirectly, by _______________
- killing the infected cells
- releasing chemicals that enhance the inflammatory response or activate other lymphocytes or macrophages.
adaptive defense involved ______________ which are not involved in innate immunity
B and T lymphocytes
Antigens
are substances that can mobilize the adaptive defenses.
They are the ultimate targets of all adaptive
immune responses
antigens
Most antigens are
large, complex molecules (natural or synthetic) that are foreign (not normally present in the body). Consequently, as far as our immune system is concerned, they are intruders, or nonself.
Antigens can be
complete or incomplete
Complete antigens have two important functional properties:
lmmunogenicity
Reactivity
lmmunogenicity
which is the ability to stimulate specific
lymphocytes to proliferate (multiply)
Reactivity
which is the ability to react with the activated
lymphocytes and the antibodies released by immunogenic reactions.
An almost limitless variety of foreign molecules can act
as complete antigens, including virtually all _______, many large ________, and some _____ and _______. Of these, ______ are the strongest antigens.
foreign proteins
polysaccharides
lipids
proteins
Pollen grains and microorganisms-such as bacteria, fungi, and virus particles are all ______ because their surfaces bear many different ___________
immunogenic
foreign macromolecules
As a rule, small molecules-such as peptides, nucleotides, and many hormones-are
not immunogenic
As a rule, small molecules-such as peptides, nucleotides, and many hormones-are not immunogenic. But if they link up with the body’s own proteins, the adaptive immune system may recognize the
combination as foreign and mount an attack that
is harmful rather than protective.
these reactions are referred to as hypersensitivities
In such cases of hypersensitivities the small troublesome molecule is called
hapten
hapten is
incomplete antigen
Unless attached to protein carriers, haptens have
reactivity but not immunogenicity.
Besides certain drugs (particularly penicillin), chemicals
that act as haptens are found in
poison ivy, animal dander, detergents, cosmetics, and a number of common household and industrial products.
The ability of a molecule to act as an antigen depends on
both its size and its complexity
Only certain parts of the antigen, called ______________ are immunogenic
antigenic determinants
Antibodies or lymphocyte receptors bind to these antigenic determinants in much the same manner that an
enzyme binds to a substrate
Most naturally occurring antigens have a variety of
antigenic determinants on their surfaces
Different lymphocytes “recognize” different
antigenic determinants, so a single antigen may mobilize several lymphocyte populations and
stimulate formation of many kinds of antibodies.
