PowerLecture: Chapter 10

PowerLecture:PowerLecture:Chapter 10Chapter 10

ImmunityImmunity

Learning ObjectivesLearning Objectives

Describe typical external barriers that Describe typical external barriers that organisms present to invading organisms.organisms present to invading organisms.

Understand how the lymphatic system Understand how the lymphatic system contributes to the body’s defenses.contributes to the body’s defenses.

Understand how vertebrates (especially Understand how vertebrates (especially mammals) recognize and discriminate mammals) recognize and discriminate between self and nonself tissues.between self and nonself tissues.

Distinguish between antibody-mediated and Distinguish between antibody-mediated and cell-mediated patterns of immune cell-mediated patterns of immune responses.responses.

Learning Objectives (cont’d)Learning Objectives (cont’d)

Describe some examples of immune Describe some examples of immune failures and identify as specifically as you failures and identify as specifically as you can which weapons in the immunity arsenal can which weapons in the immunity arsenal fail in each case.fail in each case.

Impacts/IssuesImpacts/Issues

The Face of AIDSThe Face of AIDS


Viruses, such as HIV, have Viruses, such as HIV, have wide ranging impacts on human wide ranging impacts on human health.health.

At least 40 million people are At least 40 million people are infected with HIV; 12 million infected with HIV; 12 million African children alone have been African children alone have been orphaned by AIDS.orphaned by AIDS.

Rates of new HIV infection are Rates of new HIV infection are declining in some areas, but we declining in some areas, but we still have no effective vaccine to still have no effective vaccine to prevent infection.prevent infection.


The immune system is responsible for The immune system is responsible for protecting us from HIV and other infectious protecting us from HIV and other infectious agents; the more we learn about this agents; the more we learn about this system, the more opportunities we have to system, the more opportunities we have to improve our health.improve our health.

How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main system, access “JoinIn Clicker Content” from the PowerLecture main menu. menu.

Should the federal government offer Should the federal government offer incentives to companies to discount the incentives to companies to discount the drugs for developing countries? drugs for developing countries? a. Yes, drug companies have a responsibility to a. Yes, drug companies have a responsibility to

world health, not just their bottom line. world health, not just their bottom line. b. No, if drug companies must provide subsidies, b. No, if drug companies must provide subsidies,

they won't be able to afford to develop new they won't be able to afford to develop new drugs. drugs.

Section 1Section 1

Overview of Body Overview of Body DefensesDefenses

Overview of Body DefensesOverview of Body Defenses

We are born with some general defenses We are born with some general defenses and acquire other, specific ones.and acquire other, specific ones.

We have many defenses to protect us from We have many defenses to protect us from pathogenspathogens—those viruses, bacteria, fungi, —those viruses, bacteria, fungi, protozoa, and parasitic worms that cause protozoa, and parasitic worms that cause disease.disease.

• AntigensAntigens on these pathogens identify them as on these pathogens identify them as nonself.nonself.

• Antigens are usually proteins, lipids, or Antigens are usually proteins, lipids, or oligosaccharides.oligosaccharides.


ImmunityImmunity is the body’s overall ability to resist is the body’s overall ability to resist and combat anything that is nonself.and combat anything that is nonself.

• Innate immunityInnate immunity encompasses preset responses encompasses preset responses that activate rapidly and in a generalized way to that activate rapidly and in a generalized way to

detected damage or invasion.detected damage or invasion.• Adaptive immunityAdaptive immunity responds to specific antigens on responds to specific antigens on

specific pathogens; this response takes longer to specific pathogens; this response takes longer to develop, but the body “remembers” what it sees and develop, but the body “remembers” what it sees and responds quicker the next time the same pathogen is responds quicker the next time the same pathogen is seen.seen.

Table 10.1, p.176


Three lines of defense protect the body.Three lines of defense protect the body. Intact skin and mucous membranes are Intact skin and mucous membranes are

important first-line physical barriers.important first-line physical barriers. Innate immunity forms the second line of Innate immunity forms the second line of

defense.defense. Adaptive immunity forms the third line of Adaptive immunity forms the third line of

defense.defense.


White blood cells and their chemicals are White blood cells and their chemicals are the defenders in immune responses.the defenders in immune responses.

White blood cells are the core of the White blood cells are the core of the immune immune systemsystem..

• Phagocytes release chemicals called Phagocytes release chemicals called cytokinescytokines to to further defense responses.further defense responses.

• Cytokines regulate different aspects of the immune Cytokines regulate different aspects of the immune response; response; interleukinsinterleukins affect inflammation and affect inflammation and fever, fever, interferonsinterferons defend against viruses, and defend against viruses, and tumor tumor necrosis factornecrosis factor also affects inflammation and also affects inflammation and stimulates tumor cell death.stimulates tumor cell death.


ComplementComplement is a group of about 30 blood is a group of about 30 blood proteins that can kill microbes or identify them proteins that can kill microbes or identify them for phagocytes to destroy. for phagocytes to destroy.

White blood cells serve a variety of different White blood cells serve a variety of different functions in the immune response:functions in the immune response:

• NeutrophilsNeutrophils make up two-thirds of all white blood make up two-thirds of all white blood cells and work at the site of inflammation or damage.cells and work at the site of inflammation or damage.

• BasophilsBasophils and and mast cellsmast cells produce histamines in produce histamines in response to antigens.response to antigens.

• MacrophagesMacrophages are the predominant phagocytes that are the predominant phagocytes that patrol the bloodstream.patrol the bloodstream.


• EosinophilsEosinophils target pathogens that are too large for target pathogens that are too large for the macrophages.the macrophages.

• Dendritic cellsDendritic cells signal when antigens are present in signal when antigens are present in skin and body linings.skin and body linings.

• BB and and T lymphocytesT lymphocytes (B and T cells) function in (B and T cells) function in adaptive immunity.adaptive immunity.

• Natural killer cellsNatural killer cells (NK cells) are lymphocytes that (NK cells) are lymphocytes that function in innate responses.function in innate responses.

Table 10.2, p.177

Fig. 10.1, p.177

eosinophilneutrophil

Fig. 10.1, p.177

mast cellbasophil

Fig. 10.1, p.177

B lymphocyte(B cell)

T lymphocyte(T cell)

Fig. 10.1, p.177Natural killer (NK) cell

dendritic cell

macrophage

Section 2Section 2

The Lymphatic SystemThe Lymphatic System


The The lymphatic systemlymphatic system has two key roles: has two key roles: to work with the cardiovascular system to to work with the cardiovascular system to cycle fluids back into the circulation; and to cycle fluids back into the circulation; and to circulate circulate lymphlymph from the spleen, lymph from the spleen, lymph nodes, and other lymphoid tissues nodes, and other lymphoid tissues throughout the body.throughout the body.

Fig. 10.2, p.178

Bone MarrowMarrow in some bones is production site for infection-fighting blood cells (as well as red blood cells and platelets)

TonsilsDefense against bacteria and other foreign agentsRight Lymphatic Duct

Drains right upper portion of the body

ThymusSite where certain white blood cells acquire means to chemically recognize specific foreign invaders

Thoracic DuctDrains most of the body

SpleenMajor site of antibody production; disposal site for old red blood cells and foreign debris; site of red blood cell formation in the embryo

Some of theLymph VesselsReturn excess interstitialfluid and reclaimablesolutes to the blood

Some of theLymph NodesFilter bacteria and many other agents of disease from lymph


The lymph vascular system functions in The lymph vascular system functions in drainage, delivery, and disposal.drainage, delivery, and disposal.

The The lymph vascular systemlymph vascular system consists of lymph consists of lymph capillaries and other vessels linking it to the capillaries and other vessels linking it to the cardiovascular system.cardiovascular system.

• Water and solutes that drain from the blood vessels Water and solutes that drain from the blood vessels collect in the lymphatic vessels and are returned to collect in the lymphatic vessels and are returned to the blood via these vessels.the blood via these vessels.

• The lymphatic vessels pick up absorbed fats and The lymphatic vessels pick up absorbed fats and deliver them to the blood.deliver them to the blood.

• Lymphatic vessels also transport foreign material to Lymphatic vessels also transport foreign material to the lymph nodes for disposal.the lymph nodes for disposal.


Lymph capillaries and vessels are structured Lymph capillaries and vessels are structured much like blood capillaries and veins.much like blood capillaries and veins.

Fig. 10.3a, p.179

bloodcapillary bed

a Lymph capillaries

flaplike “valve”formed fromoverlapping cellsat the tip of alymph capillary

interstitialfluid

lymphcapillary


Lymphoid organs and tissues are Lymphoid organs and tissues are specialized for body defense.specialized for body defense.

Lymph nodesLymph nodes are located at intervals along are located at intervals along the lymph vessels; lymphocytes congregate in the lymph vessels; lymphocytes congregate in these nodes, making them key battlefields in these nodes, making them key battlefields in fighting off pathogens.fighting off pathogens.

Fig. 10.3b, p.179

lymph trickles pastorganized arrays oflymphocytes withinthe lymph node

b A lymph node, cross section

valve (preventsbackflow)


The The spleenspleen filters blood and serves as a filters blood and serves as a holding station for large numbers of holding station for large numbers of lymphocytes.lymphocytes.

T cells are produced and become specialized T cells are produced and become specialized in the in the thymusthymus..

Section 3Section 3

Surface BarriersSurface Barriers


The normal microorganisms living on your The normal microorganisms living on your skin help prevent the growth of unwanted skin help prevent the growth of unwanted pathogens through competition.pathogens through competition.

Some microorganisms, such as the Some microorganisms, such as the LactobacillusLactobacillus species of the vaginal tract in species of the vaginal tract in women, lower the pH of their surroundings women, lower the pH of their surroundings to prevent growth of other microbes.to prevent growth of other microbes.

Figure 10.4Figure 10.4


The mucus coating your lungs contains The mucus coating your lungs contains enzymes such as enzymes such as lysozymelysozyme that can attack that can attack and destroy many bacteria; cilia can also and destroy many bacteria; cilia can also sweep out pathogens.sweep out pathogens.

Chemicals in tears, saliva, Chemicals in tears, saliva,

and gastric fluid offer and gastric fluid offer

similar protection.similar protection. The natural low pH of urine, as well as its The natural low pH of urine, as well as its

flushing action, helps protect the urinary tract.flushing action, helps protect the urinary tract.

Section 4Section 4

Innate ImmunityInnate Immunity


Once a pathogen enters the Once a pathogen enters the body, macrophages engulf it body, macrophages engulf it and release cytokines to and release cytokines to attract dendritic cells, attract dendritic cells, neutrophils, and more neutrophils, and more macrophages.macrophages.



Circulating complement proteins can detect Circulating complement proteins can detect pathogens and become activated.pathogens and become activated.

Activated complement attracts phagocytes, Activated complement attracts phagocytes, which can destroy the pathogens.which can destroy the pathogens.

Activated complement can also form Activated complement can also form membrane attack complexesmembrane attack complexes in the pathogen; in the pathogen; these are holes that cause the pathogen to these are holes that cause the pathogen to disintegrate.disintegrate.

Fig. 10.6, p.180

lipid bilayer ofa pathogen

one membraneattack complex(cutaway view)

pore


Activated complement and cytokines Activated complement and cytokines stimulate stimulate inflammationinflammation, characterized by , characterized by redness, swelling, warmth, and pain.redness, swelling, warmth, and pain.

Tissue irritation causes mast cells to release Tissue irritation causes mast cells to release histamine and cytokines that cause the blood histamine and cytokines that cause the blood vessels to dilate (tissue vessels to dilate (tissue

redness and warmth) redness and warmth)

and capillary walls to and capillary walls to

become leaky (become leaky (edemaedema).).



Plasma proteins and phagocytes leave the Plasma proteins and phagocytes leave the blood vessels.blood vessels.

• Plasma proteins contain clotting agents that help wall Plasma proteins contain clotting agents that help wall off the pathogen and promote repair of tissues.off the pathogen and promote repair of tissues.

• Macrophages release cytokines that tell the brain to Macrophages release cytokines that tell the brain to release prostaglandins, which in turn stimulates release prostaglandins, which in turn stimulates feverfever production; moderate fevers inhibit pathogen production; moderate fevers inhibit pathogen growth.growth.

Fig. 10.7, p.181

Bacteria invade a tissue and directly kill cells or releasemetabolic products that damage tissue.

a b Mast cells in tissue release histamine, which then triggers arteriolar vasodilation (hence redness and warmth) as well as increased capillary permeability.

Fluid and plasmaproteins leak out ofcapillaries; localizededema (tissue swelling)and pain result.

Plasmaproteins attackbacteria. Clottingfactors wall offinflamed area.

Neutrophils, macrophages, andother phagocytes engulf invaders and debris. Activated complement attracts phagocytes and directly kills invaders.

c d e

ab

c d

e

Section 5Section 5

Overview of Overview of

Adaptive DefensesAdaptive Defenses

Overview of Adaptive DefensesOverview of Adaptive Defenses

Adaptive immunity has three key features.Adaptive immunity has three key features. Adaptive immunity is the body’s third line of Adaptive immunity is the body’s third line of

defense and has three defining features:defense and has three defining features:• Adaptive immunity is Adaptive immunity is specificspecific; each B and T cell only ; each B and T cell only

recognizes one antigen.recognizes one antigen.• Adaptive immunity is Adaptive immunity is diversediverse; B and T cells ; B and T cells

collectively can recognize at least a billion different collectively can recognize at least a billion different threats.threats.

• Adaptive immunity has Adaptive immunity has memorymemory..


Recognition of an antigen results in rapid cell Recognition of an antigen results in rapid cell division to produce huge numbers of identical B division to produce huge numbers of identical B and T cells that recognize the stimulating and T cells that recognize the stimulating antigen.antigen.

• Some of these new cells are Some of these new cells are effector cellseffector cells that can that can immediately destroy pathogens.immediately destroy pathogens.

• Others are Others are memory cellsmemory cells, held in reserve for future , held in reserve for future battles against the same threat; memory cells are battles against the same threat; memory cells are what make you “immune” to various pathogens.what make you “immune” to various pathogens.


B cells and T cells become specialized to B cells and T cells become specialized to attack antigens in different ways.attack antigens in different ways.

Both B and T lymphocytes arise in stem cells in Both B and T lymphocytes arise in stem cells in the bone marrow.the bone marrow.

• B cells continue to develop within bone marrow.B cells continue to develop within bone marrow.• T cells travel to the thymus to finish developing; T T cells travel to the thymus to finish developing; T

cells divide into two populations—cells divide into two populations—helper T cellshelper T cells and and cytotoxic cytotoxic (“killer”) (“killer”) T cellsT cells..

When mature, B and T cells can be found in the When mature, B and T cells can be found in the lymph nodes, spleen, and other lymphoid lymph nodes, spleen, and other lymphoid tissues where they remain “naive” until they tissues where they remain “naive” until they recognize antigen. recognize antigen.

Overview of Overview of Adaptive DefensesAdaptive Defenses

B cells and T cells respond to pathogens in B cells and T cells respond to pathogens in different ways.different ways.• B cells produce B cells produce antibodiesantibodies (proteins) and are (proteins) and are

responsible for responsible for antibody-mediated antibody-mediated

immunityimmunity..• T cells directly attack invaders; their response is T cells directly attack invaders; their response is

called called cell-mediated immunitycell-mediated immunity..


Fig. 10.9, p.182

Bone marrowRed blood cellsPlateletsMonocytes,others

Cell-mediatedimmune response

Antibody-mediatedimmune response

T cellsB cells

Stem cells

Foreigninvasion

Organs of lymphatic system

T cellsB cells

Thymus

Fig. 10.10, p.183

antigen-presenting cells

Antibody-MediatedImmune Response

Cell-MediatedImmune Response

inactive B cells+

antigen+

complement

activatedB cells

effector B cells+

memory B cells

effector cytotoxic T cells+

memory cytotoxic cells

effectorhelper T cells

+memory

helper T cells

inactive helper T cells

inactivecytotoxic T cells


Proteins called MHC markers label body Proteins called MHC markers label body cells as self.cells as self.

All body cells have All body cells have MHC markersMHC markers (from (from MMajor ajor HHistocompatibility istocompatibility CComplex genes) to identify omplex genes) to identify them as “self.”them as “self.”

T cells have T cells have TCRsTCRs ( (TT CCell ell RReceptors) that see eceptors) that see MHC in context with antigen and respond.MHC in context with antigen and respond.


Antigen-presenting cells introduce antigens Antigen-presenting cells introduce antigens to T cells and B cells.to T cells and B cells.

T cells and B cells can only “see” antigens that T cells and B cells can only “see” antigens that have been processed by an have been processed by an antigen-antigen-presenting cellpresenting cell (APC). (APC).

• Macrophages, dendritic cells, and B cells can all Macrophages, dendritic cells, and B cells can all present antigen.present antigen.

• The antigen is ingested and digested; then its The antigen is ingested and digested; then its fragments are linked with MHC markers and fragments are linked with MHC markers and displayed on the cell’s surface as displayed on the cell’s surface as antigen-MHC antigen-MHC complexescomplexes..


Helper T cells see the antigen-MHC complex, Helper T cells see the antigen-MHC complex, release cytokines, and trigger repeated rounds release cytokines, and trigger repeated rounds of division to produce the large numbers of of division to produce the large numbers of activated B and T cells.activated B and T cells.

• Specialization of activated cells into effector or Specialization of activated cells into effector or memory cells also occurs.memory cells also occurs.

• An effector B cell is called a An effector B cell is called a plasma cellplasma cell; it can flood ; it can flood the bloodstream with antibodies.the bloodstream with antibodies.

Table 10.3, p.192

Section 6Section 6

Antibody-Mediated Antibody-Mediated Immunity: Defending Immunity: Defending

Against Threats Outside Against Threats Outside CellsCells

Antibody-Mediated Immunity: Defending Antibody-Mediated Immunity: Defending Against Threats Outside CellsAgainst Threats Outside Cells

Antibodies develop while B cells are in bone Antibodies develop while B cells are in bone marrow.marrow.

An antibody has a Y-shaped protein structure; An antibody has a Y-shaped protein structure; antigens are bound by the two “arms” of the antigens are bound by the two “arms” of the antibody.antibody.

No two B cells make antibodies that are alike; No two B cells make antibodies that are alike; this allows both diversity and specificity.this allows both diversity and specificity.

B cells make many copies of their antibodies, B cells make many copies of their antibodies, which are inserted in the plasma membrane, which are inserted in the plasma membrane, arms sticking out and ready to bind antigen.arms sticking out and ready to bind antigen.

binding site for antigen binding site for antigen

Fig. 10.11a, p.184

antigen on bacterial cell(not to scale)

Fig. 10.11b, p. 184

binding site on one kind of antibody molecule for a specific antigen


Antibodies target pathogens that are Antibodies target pathogens that are outside cells.outside cells.

Prior to activation, B cells serve as antigen-Prior to activation, B cells serve as antigen-presenting cells.presenting cells.

• Antibodies on the B cell surface bind antigens, Antibodies on the B cell surface bind antigens, internalize them, process them, and then display internalize them, process them, and then display antigen-MHC complexes.antigen-MHC complexes.

• TCRs of a helper T cell see the antigen-MHC TCRs of a helper T cell see the antigen-MHC complex and bind; binding causes the cells to complex and bind; binding causes the cells to exchange signals.exchange signals.

• The T cell disengages, but the B cell is now The T cell disengages, but the B cell is now activated; when it recognizes unbound antigen, the B activated; when it recognizes unbound antigen, the B cell will divide into plasma cells and memory cells.cell will divide into plasma cells and memory cells.

bacterium

Fig. 10.12, p. 185

dendritic cell

inactiveT cell

effectorhelperT cell

inactiveB cell

B cell

memoryB cell

effectorB cell

memoryhelperT cell

cytokines

complement

antigen-presenting cell


Plasma cells can release up to 2,000 antibodies Plasma cells can release up to 2,000 antibodies per minute into the bloodstream; these per minute into the bloodstream; these antibodies “flag” invaders for destruction by antibodies “flag” invaders for destruction by phagocytes and complement.phagocytes and complement.

There are five classes of antibodies, each There are five classes of antibodies, each with a particular function.with a particular function.

Collectively, antibodies are referred to as Collectively, antibodies are referred to as immunoglobulinsimmunoglobulins, or Igs., or Igs.


The five different classes of Igs are the protein The five different classes of Igs are the protein products of gene shuffling that takes place as products of gene shuffling that takes place as the B cells mature:the B cells mature:

• IgMIgM antibodies cluster into a structure with 10 antibodies cluster into a structure with 10 binding sites, making them more efficient at binding binding sites, making them more efficient at binding clumped targets; IgM is the first antibody produced in clumped targets; IgM is the first antibody produced in a response.a response.

• IgAIgA antibodies are present in secretions of exocrine antibodies are present in secretions of exocrine glands (tears, saliva, breast milk) and in the mucus glands (tears, saliva, breast milk) and in the mucus of the respiratory, digestive, and reproductive tracts.of the respiratory, digestive, and reproductive tracts.


• IgGIgG antibodies neutralize toxins, turn on antibodies neutralize toxins, turn on complement, are long lasting, can cross the complement, are long lasting, can cross the placenta, and are found in mother’s milk.placenta, and are found in mother’s milk.

• IgDIgD is the most common antibody bound to naive B is the most common antibody bound to naive B cells; it may help activate T cells.cells; it may help activate T cells.

• IgEIgE antibodies are involved in allergic reactions; they antibodies are involved in allergic reactions; they bind to basophils and mast cells where they act as bind to basophils and mast cells where they act as traps for antigen, causing the release of histamine.traps for antigen, causing the release of histamine.

IgG, IgD, and IgE IgA IgM

In-text Fig., p.184

Section 7Section 7

Cell-Mediated Cell-Mediated Responses—Defending Responses—Defending Against Threats Inside Against Threats Inside

CellsCells

Cell-Mediated Responses – Defending Cell-Mediated Responses – Defending Against Threats Inside CellsAgainst Threats Inside Cells

Cell-mediated responses fight those Cell-mediated responses fight those pathogens (viruses, bacteria, and some pathogens (viruses, bacteria, and some fungi and protozoans) that can enter cells to fungi and protozoans) that can enter cells to avoid antibody defenses; cell-mediated avoid antibody defenses; cell-mediated responses also fight abnormal body cells responses also fight abnormal body cells such as cancer cells.such as cancer cells.

APCs present antigen to T cells, similar to APCs present antigen to T cells, similar to their role in antibody-mediated immunity.their role in antibody-mediated immunity.


Helper T cells can be stimulated this way to Helper T cells can be stimulated this way to divide into effector and memory cells.divide into effector and memory cells.

Effector helper T cells or APCs directly can Effector helper T cells or APCs directly can stimulate cytotoxic T cells to divide.stimulate cytotoxic T cells to divide.

• Cytotoxic T cells rapidly multiply and release Cytotoxic T cells rapidly multiply and release molecules that can “touch-kill” infected and abnormal molecules that can “touch-kill” infected and abnormal body cells.body cells.

• Cytotoxic T cells also secrete chemicals that Cytotoxic T cells also secrete chemicals that stimulate stimulate apoptosisapoptosis—the programmed cell death of —the programmed cell death of the infected cell.the infected cell.

Fig. 10.14, p.187

cytotoxic T cell

tumor cell

Fig. 10.13, p. 186

virus particle(red) infectinga body cell(yellow)

dendritic cell

inactivehelperT cell


memoryhelperT cell


inactivecytotoxic

T cell

activatedcytotoxic

T cell

memorycytotoxic

T cell

effectorcytotoxic

T cell

effectorcytotoxic

T cell

a

b c

d

e

cytokines

Fig. 10.13, p. 186

virus particle( red) infectinga body cell( yellow)

dendritic cell


effectorcytotoxic

T cell

a

b c

d

e

Stepped Art

inactivehelperT cell

inactivecytotoxic

T cell

activatedcytotoxic

T cell


memoryhelperT cell

effectorcytotoxic

T cell

memorycytotoxic

T cell


Helper T cells can also stimulate NK cells; they Helper T cells can also stimulate NK cells; they will attack any cell that has too few or altered will attack any cell that has too few or altered MHC, any cells that have been tagged by MHC, any cells that have been tagged by antibodies, and cells showing “stress markers” antibodies, and cells showing “stress markers” as indicators of infection or cancer.as indicators of infection or cancer.

Cytotoxic T cells cause the body to reject Cytotoxic T cells cause the body to reject transplanted tissue.transplanted tissue.

During organ transplants, donor tissues must During organ transplants, donor tissues must be matched to a recipient to ensure that the be matched to a recipient to ensure that the MHC markers do not differ enough to stimulate MHC markers do not differ enough to stimulate rejection by cytotoxic T cells.rejection by cytotoxic T cells.


• Donor and recipient usually must share at least 75% Donor and recipient usually must share at least 75% of their MHC markers for the transplant to succeed; of their MHC markers for the transplant to succeed; close relatives make the best donors because of this.close relatives make the best donors because of this.

• Recipients usually also take drugs to suppress the Recipients usually also take drugs to suppress the immune system to prevent rejection; often they will immune system to prevent rejection; often they will also take antibiotics to ward off potential infections.also take antibiotics to ward off potential infections.

Tissues of the eye and testicles do not Tissues of the eye and testicles do not stimulate rejection; instead, cells of these stimulate rejection; instead, cells of these tissues secrete signals that cause lymphocytes tissues secrete signals that cause lymphocytes to undergo apoptosis, thus preventing the to undergo apoptosis, thus preventing the lymphocytes from attacking. lymphocytes from attacking.

Section 8Section 8

Immunological MemoryImmunological Memory

Immunological MemoryImmunological Memory

Memory cells form during the Memory cells form during the primaryprimary (first)(first) responseresponse to an antigen and remain to an antigen and remain in the blood for years or decades.in the blood for years or decades.

Secondary responsesSecondary responses to the same to the same antigen are much faster; plasma cells and antigen are much faster; plasma cells and effector T cells form sooner and in greater effector T cells form sooner and in greater numbers, preventing infectionnumbers, preventing infection..

Fig. 10.20, p.194

Fig. 10.15b, p. 188

later exposure to same antigen

first exposure to antigen

Rel

ativ

e co

nce

ntr

atio

ns

of

anti

bo

dy

Response time (weeks)

First exposureto antigenprovokesprimaryimmuneresponse.

effector cell memory cell

effector cells memory cells

inactive T or B cell

Fig. 10.15a, p. 188

Laterexposure to same antigenprovokessecondaryimmuneresponse.

Section 9Section 9

Applications of Applications of ImmunologyImmunology

Applications of ImmunologyApplications of Immunology

Immunization gives “borrowed” immunity.Immunization gives “borrowed” immunity. ImmunizationImmunization increases immunity against increases immunity against

specific diseases.specific diseases. In In active immunizationactive immunization, a , a

vaccinevaccine is given by injection or is given by injection or is taken orally.is taken orally.

• The first dose of vaccine elicits a primary immune The first dose of vaccine elicits a primary immune response; a second dose (“booster”) elicits a response; a second dose (“booster”) elicits a secondary, and more long-lasting, response.secondary, and more long-lasting, response.

• Vaccines are made from killed or very weak Vaccines are made from killed or very weak pathogens, inactivated forms of toxins, or transgenic pathogens, inactivated forms of toxins, or transgenic (genetically engineered) viruses.(genetically engineered) viruses.



PassivePassive immunizationimmunization involves injecting involves injecting antibodies into already infected individuals.antibodies into already infected individuals.

Vaccines are not risk free.Vaccines are not risk free.

p. 188


Monoclonal antibodies are used in research Monoclonal antibodies are used in research and medicine.and medicine.

Monoclonal antibodiesMonoclonal antibodies are antibodies made by are antibodies made by cells cloned from a single cells cloned from a single antibody-producing B cell; antibody-producing B cell; they are generally produced using genetically they are generally produced using genetically altered bacteria or sometimes plants.altered bacteria or sometimes plants.

Monoclonal antibodies are being used Monoclonal antibodies are being used commercially in home pregnancy tests, commercially in home pregnancy tests, screening for prostate cancer, and other uses.screening for prostate cancer, and other uses.



Immunotherapies reinforce defenses.Immunotherapies reinforce defenses. ImmunotherapyImmunotherapy alters the body’s own immune alters the body’s own immune

mechanisms to enhance defense against mechanisms to enhance defense against infections and cancer.infections and cancer.

• Cytokines can be used to activate B and T cells to Cytokines can be used to activate B and T cells to fight cancer.fight cancer.

• Monoclonal antibodies can be used to bind to Monoclonal antibodies can be used to bind to proteins on cancer cells to draw NK cells to the proteins on cancer cells to draw NK cells to the tumor.tumor.


• Other monoclonal antibodies are bound to toxins to Other monoclonal antibodies are bound to toxins to make make immunotoxinsimmunotoxins; these substances bind to ; these substances bind to cancer cells, enter them, and prevent growth.cancer cells, enter them, and prevent growth.

• GammaGamma interferon, produced by T cells, stimulates interferon, produced by T cells, stimulates NK cells and boosts activity of macrophages; it is NK cells and boosts activity of macrophages; it is currently being used to treat hepatitis C.currently being used to treat hepatitis C.

• BetaBeta interferon is being used to treat interferon is being used to treat multiple multiple sclerosissclerosis..

Immunotherapies, as with vaccines, do not Immunotherapies, as with vaccines, do not come without risks.come without risks.

Section 10Section 10

Disorders of the Immune Disorders of the Immune SystemSystem

Disorders of the Immune SystemDisorders of the Immune System

In allergies, harmless substances provoke In allergies, harmless substances provoke an immune attack.an immune attack.

An An allergyallergy is an immune is an immune response to a normally response to a normally harmless substance harmless substance called an called an allergenallergen..

• Allergens include: pollen, some foods and drugs, Allergens include: pollen, some foods and drugs, dust mites, fungal spores, insect venom, and certain dust mites, fungal spores, insect venom, and certain ingredients in cosmetics.ingredients in cosmetics.

• Allergens trigger mild to severe inflammation of Allergens trigger mild to severe inflammation of various tissues.various tissues.

• A variety of causes, from genetic to emotional, lead A variety of causes, from genetic to emotional, lead to allergies.to allergies. Figure 10.18aFigure 10.18a


Exposure to an allergen triggers production of Exposure to an allergen triggers production of IgE antibodies, which cause the release of IgE antibodies, which cause the release of histamines and prostaglandins from mast cells.histamines and prostaglandins from mast cells.

• Histamines and prostaglandins fuel inflammation.Histamines and prostaglandins fuel inflammation.• Hay feverHay fever manifests as stuffed sinuses, a drippy manifests as stuffed sinuses, a drippy

nose, and sneezing.nose, and sneezing. In a few individuals, explosive inflammatory In a few individuals, explosive inflammatory

responses trigger life-threatening responses trigger life-threatening anaphylacticanaphylactic shockshock in which air passages constrict and fluid in which air passages constrict and fluid rushes out of the capillaries.rushes out of the capillaries.


• Food allergies, such as peanut allergies, and wasp Food allergies, such as peanut allergies, and wasp and bee venom allergies, can trigger anaphylactic and bee venom allergies, can trigger anaphylactic shock.shock.

• Rapid injections of the hormone epinephrine can Rapid injections of the hormone epinephrine can prevent shock and save lives.prevent shock and save lives.

AntihistaminesAntihistamines are often used to relieve the are often used to relieve the short-term symptoms of allergies; short-term symptoms of allergies; desensitizationdesensitization can be used to “train” the body can be used to “train” the body not to see allergens.not to see allergens.

allergen (antigen)enters the body

histaminegranules

IgEantibodies

mast cell

B cell

IgE antibodies attach to mast cells in tissues, which have granules containing histaminemolecules

Fig. 10.18b, p. 190

nucleusmitochondrion

Effector B cells (plasma cells)produce and secrete IgE antibodies to the allergen

Allergen binds B cell receptors; thesensitized B cell nowprocesses the antigenand, with the help of Tcells (not shown), proceeds through the steps leading to cell proliferation

histaminegranules

SECONDARY RESPONSE

(allergy)

Fig. 10.18b, p. 190

After the first exposure, whenthe allergen enters the body itbinds with IgE antibodies onmast cells; binding stimulatesthe mast cell to release histamine and other substances


Autoimmune disorders attack “self.”Autoimmune disorders attack “self.” In an In an autoimmune responseautoimmune response, lymphocytes , lymphocytes

turn against the body’s own cells.turn against the body’s own cells. Examples of autoimmune diseases include the Examples of autoimmune diseases include the

following:following:• Rheumatoid arthritisRheumatoid arthritis, an inflammation of the joints , an inflammation of the joints

caused by immune attack against collagen and caused by immune attack against collagen and antibodies in the joints; antibodies in the joints;

inflammation, complement inflammation, complement

and faulty repair mechanisms and faulty repair mechanisms

contribute to the damage.contribute to the damage.



• Type 1 diabetesType 1 diabetes, a type of , a type of diabetes mellitusdiabetes mellitus, , caused when the immune system attacks and caused when the immune system attacks and destroys the insulin-secreting cells of the pancreas, destroys the insulin-secreting cells of the pancreas, impairing glucose absorption from the blood.impairing glucose absorption from the blood.

• Systemic lupus erythematosusSystemic lupus erythematosus, where patients , where patients develop antibodies to their own DNA and other “self” develop antibodies to their own DNA and other “self” components.components.

Autoimmune diseases tend to be more frequent Autoimmune diseases tend to be more frequent in women than in men. in women than in men.


Immune responses can be deficient.Immune responses can be deficient. ImmunodeficiencyImmunodeficiency is used to describe the is used to describe the

state where a person’s immune system is state where a person’s immune system is weakened or lacking; under these conditions weakened or lacking; under these conditions the body is vulnerable and infections that would the body is vulnerable and infections that would normally not be serious become life normally not be serious become life threatening.threatening.


In In severe combined immune deficiencysevere combined immune deficiency (SCID) both B and T cells are in low numbers; (SCID) both B and T cells are in low numbers; infants born with SCID usually die early in life.infants born with SCID usually die early in life.

In In acquired immune deficiency syndromeacquired immune deficiency syndrome (AIDS), the HIV virus attacks the body’s (AIDS), the HIV virus attacks the body’s macrophages and helper T cells, crippling the macrophages and helper T cells, crippling the immune response.immune response.

PowerLecture: Chapter 10

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