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Overview: Reconnaissance, Recognition, and ResponseBarriers help an animal to defend itself from the many dangerous pathogens it may encounter. The immune system recognizes foreign bodies = “not self” and responds with

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Слайд 1Chapter 43
The Immune System

Chapter 43The Immune System

Слайд 2Overview: Reconnaissance, Recognition, and Response
Barriers help an animal to defend

itself from the many dangerous pathogens it may encounter.
The

immune system recognizes foreign bodies = “not self” and responds with the production of immune cells and proteins.
Two major kinds of defense have evolved: innate immunity and acquired immunity.
Overview: Reconnaissance, Recognition, and ResponseBarriers help an animal to defend itself from the many dangerous pathogens it

Слайд 3How do immune cells of animals recognize foreign cells?
1.5

How do immune cells of animals recognize foreign cells? 1.5 µm

Слайд 4Innate immunity is present before any exposure to pathogens and

is effective from the time of birth.
It involves nonspecific responses

to pathogens.
Innate immunity consists of external barriers plus internal cellular and chemical defenses.
Innate immunity is present before any exposure to pathogens and is effective from the time of birth.It

Слайд 5Acquired immunity = adaptive immunity, develops after exposure to agents

such as microbes, toxins, or other foreign substances.
It involves a

very specific response to pathogens.
Acquired immunity = adaptive immunity, develops after exposure to agents such as microbes, toxins, or other foreign

Слайд 6 Animal Immunity
INNATE IMMUNITY

Recognition of traits
shared by broad ranges
of

pathogens, using a
small set of receptors
Non-specific




Rapid response

Recognition of traits
specific to

particular
pathogens, using a vast
array of receptors


Slower response

ACQUIRED IMMUNITY

Pathogens
(microorganisms
and viruses)

Barrier defenses:
Skin
Mucous membranes
Secretions

Internal defenses:
Phagocytic cells
Antimicrobial proteins
Inflammatory response
Natural killer cells

Humoral response:
Antibodies defend against
infection in body fluids.

Cell-mediated response:
Cytotoxic lymphocytes defend
against infection in body cells.

Animal Immunity INNATE IMMUNITYRecognition of traitsshared by broad rangesof pathogens, using asmall set of receptorsNon-specific••Rapid

Слайд 7For Innate Immunity, recognition and response rely on shared traits

of pathogens
Both invertebrates and vertebrates depend on innate immunity to

fight infection. Vertebrates also develop acquired immune defenses.
The immune system recognizes bacteria and fungi by structures on their cell walls.
An immune response varies with the class of pathogen encountered.
For Innate Immunity, recognition and response rely on shared traits of pathogensBoth invertebrates and vertebrates depend on

Слайд 8Innate Immunity of Invertebrates
In insects, an exoskeleton made of chitin

forms the first barrier to pathogens.
The digestive system is protected

by low pH and lysozyme, an enzyme that digests microbial cell walls.
Hemocytes circulate within hemolymph and carry out phagocytosis, the ingestion and digestion of foreign substances including bacteria.
Hemocytes also secrete antimicrobial peptides that disrupt the plasma membranes of bacteria.
Innate Immunity of InvertebratesIn insects, an exoskeleton made of chitin forms the first barrier to pathogens.The digestive

Слайд 9 Phagocytosis
Microbes

PHAGOCYTIC CELL

Vacuole
Lysosome
Containing
hydrolytic
enzymes

PhagocytosisMicrobesPHAGOCYTIC CELLVacuoleLysosomeContaininghydrolytic enzymes

Слайд 10Innate Immunity Defenses of Vertebrates
The immune system of mammals is

the best understood of the vertebrates.
Innate defenses include barrier defenses,

phagocytosis, antimicrobial peptides.
Additional defenses are unique to vertebrates: the inflammatory response and natural killer cells.
Innate Immunity Defenses of VertebratesThe immune system of mammals is the best understood of the vertebrates.Innate defenses

Слайд 11Barrier Defenses
Barrier defenses include the skin and mucous membranes of

the respiratory, urinary, and reproductive tracts.
Mucus traps and allows for

the removal of microbes.
Many body fluids including saliva, mucus, and tears are hostile to microbes.
The low pH of skin and the digestive system prevents growth of microbes.
Barrier DefensesBarrier defenses include the skin and mucous membranes of the respiratory, urinary, and reproductive tracts.Mucus traps

Слайд 12Cellular Innate Defenses
White blood cells = leukocytes engulf pathogens in

the body via phagocytosis.
Groups of pathogens are recognized by TLR,

Toll-like receptors.


Cellular Innate DefensesWhite blood cells = leukocytes engulf pathogens in the body via phagocytosis.Groups of pathogens are

Слайд 13 TLR signaling
EXTRACELLULAR
FLUID
Lipopolysaccharide
Flagellin
TLR4
TLR5
Helper
protein
TLR9
TLR3
WHITE
BLOOD
CELL
VESICLE
CpG DNA
ds RNA
Inflammatory
responses

TLR signaling EXTRACELLULARFLUIDLipopolysaccharideFlagellinTLR4TLR5HelperproteinTLR9TLR3WHITEBLOODCELLVESICLECpG DNAds RNAInflammatoryresponses

Слайд 14A white blood cell engulfs a microbe, then fuses with

a lysosome to destroy the microbe.
There are different types of

phagocytic cells:
Neutrophils engulf and destroy microbes.
Macrophages are part of the lymphatic system and are found throughout the body.
Eosinophils discharge destructive enzymes.
Dendritic cells stimulate development of acquired immunity.
A white blood cell engulfs a microbe, then fuses with a lysosome to destroy the microbe.There are

Слайд 15Lymphatic System
Adenoid

Tonsil

Lymph
nodes

Spleen
Peyer’s patches
(small intestine)
Appendix
Lymphatic
vessels
Lymph
node
Masses of
defensive cells
Blood
capillary
Lymphatic
vessel
Tissue
cells
Interstitial fluid

Lymphatic System AdenoidTonsilLymphnodesSpleenPeyer’s patches(small intestine)AppendixLymphaticvesselsLymphnodeMasses ofdefensive cellsBloodcapillaryLymphaticvesselTissuecellsInterstitial fluid

Слайд 16Antimicrobial Peptides and Proteins
Peptides and proteins function in innate defense

by attacking microbes directly or impeding their reproduction.
Interferon proteins provide

innate defense against viruses and help activate macrophages.
About 30 proteins make up the complement system, which causes lysis of invading cells and helps trigger inflammation.

Antimicrobial Peptides and ProteinsPeptides and proteins function in innate defense by attacking microbes directly or impeding their

Слайд 17Inflammatory Responses
Following an injury, mast cells release histamine, which promotes

changes in blood vessels; this is part of the inflammatory

response.
These changes increase local blood supply and allow more phagocytes and antimicrobial proteins to enter tissues.
Pus = a fluid rich in white blood cells, dead microbes, and cell debris, accumulates at the site of inflammation.
Inflammatory ResponsesFollowing an injury, mast cells release histamine, which promotes changes in blood vessels; this is part

Слайд 18 Major events in a local Inflammatory Response
Pathogen
Splinter
Macrophage
Mast cell
Chemical
signals
Capillary
Phagocytic cell
Red

blood cells
Fluid
Phagocytosis
1.
2.
3.

Major events in a local Inflammatory ResponsePathogenSplinterMacrophageMast cellChemicalsignalsCapillaryPhagocytic cellRed blood cellsFluidPhagocytosis1.2.3.

Слайд 19Inflammation can be either local or systemic (throughout the body).
Fever

is a systemic inflammatory response triggered by pyrogens released by

macrophages, and toxins from pathogens.
Septic shock is a life-threatening condition caused by an overwhelming inflammatory response.

Inflammation can be either local or systemic (throughout the body).Fever is a systemic inflammatory response triggered by

Слайд 20Natural Killer Cells
All body cells (except red blood cells) have

a class I MHC protein on their surface.
MHC =

Major Histocompatibility Complex , part of the extracellular matrix.
Class II MHC protein molecules are found on specialized cells
Cancerous or infected cells no longer express this MHC protein; natural killer (NK) cells attack these damaged cells.
Natural Killer CellsAll body cells (except red blood cells) have a class I MHC protein on their

Слайд 21Innate Immune System Evasion by Pathogens
Some pathogens avoid destruction by

modifying their surface to prevent recognition or by resisting breakdown

following phagocytosis.
Tuberculosis (TB) is one such disease and kills more than a million people a year.
Innate Immune System Evasion by PathogensSome pathogens avoid destruction by modifying their surface to prevent recognition or

Слайд 22In Acquired Immunity, lymphocyte receptors provide pathogen-specific recognition
White blood cells

called lymphocytes recognize and respond to antigens, foreign molecules.
Lymphocytes that

mature in the thymus above the heart are called T cells, and those that mature in bone marrow are called B cells.
Lymphocytes contribute to immunological memory, an enhanced response to a foreign molecule encountered previously.
Cytokines are secreted by macrophages and dendritic cells to recruit and activate lymphocytes.

In Acquired Immunity, lymphocyte receptors provide pathogen-specific recognitionWhite blood cells called lymphocytes recognize and respond to antigens,

Слайд 23Acquired Immunity = Active Immunity: Specific
B cells and T cells

have receptor proteins that can bind to foreign molecules.
Each individual

lymphocyte is specialized to recognize a specific type of molecule.
An antigen is any foreign molecule to which a lymphocyte responds.
A single B cell or T cell has about 100,000 identical antigen receptors.

Acquired Immunity = Active Immunity: SpecificB cells and T cells have receptor proteins that can bind to

Слайд 24 Antigen receptors on lymphocytes

Antigen-
binding
site



Antigen-
binding site
Antigen-
binding
site
Disulfide
bridge

Variable
regions
Constant
regions
Transmembrane
region
Plasma
membrane
Light
chain
Heavy chains
T cell
 chain
 chain
Disulfide bridge
Cytoplasm

of T cell

T cell receptor

Cytoplasm of B cell

B cell receptor

B cell

V

V

C

C

V

V

C

C

C

C

V

V

Antigen receptors on lymphocytes  Antigen-bindingsite     Antigen-binding siteAntigen-bindingsiteDisulfidebridge  VariableregionsConstantregionsTransmembraneregionPlasmamembraneLightchainHeavy chainsT cell

Слайд 25All antigen receptors on a single lymphocyte recognize the same

epitope, or antigenic determinant, on an antigen.
B cells give rise

to plasma cells, which secrete proteins called antibodies or immunoglobulins.

All antigen receptors on a single lymphocyte recognize the same epitope, or antigenic determinant, on an antigen.B

Слайд 26 Epitopes =

antigen determinants
Antigen-binding sites

Antigen-
binding
sites

Epitopes
(antigenic
determinants)
Antigen
Antibody B
Antibody C
Antibody A


C
C
C
V
V
V
V
C

Epitopes = antigen determinants Antigen-binding sitesAntigen-bindingsitesEpitopes(antigenicdeterminants)AntigenAntibody BAntibody CAntibody

Слайд 27The Antigen Receptors of B Cells and T Cells
B cell

receptors bind to specific, intact antigens.
The B cell receptor consists

of two identical heavy chains and two identical light chains.
The tips of the chains form a constant (C) region, and each chain contains a variable (V) region, so named because its amino acid sequence varies extensively from one B cell to another.
Secreted antibodies, or immunoglobulins, are structurally similar to B cell receptors but lack transmembrane regions that anchor receptors in the plasma membrane.

The Antigen Receptors of B Cells and T CellsB cell receptors bind to specific, intact antigens.The B

Слайд 28Each T cell receptor consists of two different polypeptide chains.

The tips of the chain form a variable (V) region;

the rest is a constant (C) region.
T cells can bind to an antigen that is free or on the surface of a pathogen.
T cells bind to antigen fragments presented on a host cell. These antigen fragments are bound to cell-surface proteins called MHC molecules.
MHC molecules are so named because they are encoded by a family of genes (many unique / specific) called the Major Histocompatibility Complex.


Each T cell receptor consists of two different polypeptide chains. The tips of the chain form a

Слайд 29The Role of the MHC
In infected cells, MHC molecules bind

and transport antigen fragments to the cell surface, a process

called antigen presentation.
A nearby T cell can then detect the antigen fragment displayed on the cell’s surface.
Depending on their source, peptide antigens are handled by different classes of MHC molecules.

The Role of the MHCIn infected cells, MHC molecules bind and transport antigen fragments to the cell

Слайд 30Antigen Presentation by an MHC molecule
Antigen

Top view: binding surface
exposed to

antigen receptors

Plasma
membrane of
infected cell
Antigen

Class I MHC
molecule

Antigen Presentation by an MHC moleculeAntigenTop view: binding surfaceexposed to antigen receptorsPlasmamembrane ofinfected cellAntigenClass I MHCmolecule

Слайд 31Class I MHC molecules are found on almost all nucleated

cells of the body.
They display peptide antigens to cytotoxic T

cells.
Class II MHC molecules are found on specialized cells: macrophages, B cells, and activated T cells…
Class I MHC molecules are found on almost all nucleated cells of the body.They display peptide antigens

Слайд 32 Interaction of T cells with Antigen-Presenting Cells
Infected

cell
Antigen
fragment
Class I MHC
molecule
T cell
receptor
(a)
Antigen
associates
with MHC
molecule
T cell
recognizes
combination
Cytotoxic T cell
(b)
Helper T cell
T

cell
receptor

Class II MHC
molecule

Antigen
fragment

Antigen-
presenting
cell

Microbe

1

1

1

2

2

2

Interaction of T cells with Antigen-Presenting Cells Infected cellAntigenfragmentClass I MHCmoleculeT cellreceptor(a)Antigenassociateswith MHCmoleculeT cellrecognizescombinationCytotoxic

Слайд 33Class II MHC molecules are located mainly on dendritic cells,

macrophages, and B cells.
Dendritic cells, macrophages, and B cells are

antigen-presenting cells that display antigens on their surface to cytotoxic T cells and helper T cells.
Class II MHC molecules are located mainly on dendritic cells, macrophages, and B cells.Dendritic cells, macrophages, and

Слайд 34Lymphocyte Development
The acquired immune system has three important properties:
Receptor Diversity
Lack

of reactivity against host cells
Immunological Memory

Lymphocyte DevelopmentThe acquired immune system has three important properties:Receptor DiversityLack of reactivity against host cellsImmunological Memory

Слайд 35Generation of Lymphocyte Diversity by Gene Rearrangement
Differences in the variable

region account for specificity of antigen receptors.
The immunoglobulin (Ig) gene

encodes one chain of the B cell receptor.
Many different chains can be produced from the same Ig chain gene by rearrangement of the DNA.
Rearranged DNA is transcribed and translated and the antigen receptor formed.
Generation of Lymphocyte Diversity by Gene RearrangementDifferences in the variable region account for specificity of antigen receptors.The

Слайд 36Origin of Self-Tolerance
Antigen receptors are generated by random rearrangement of

DNA.
As lymphocytes mature in bone marrow or the thymus, they

are tested for self-reactivity.
Lymphocytes with receptors specific for the body’s own molecules are destroyed by apoptosis, or rendered nonfunctional.

Origin of Self-ToleranceAntigen receptors are generated by random rearrangement of DNA.As lymphocytes mature in bone marrow or

Слайд 37Amplifying Lymphocytes by Clonal Selection
In the body there are few

lymphocytes with antigen receptors for any particular epitope.
The binding of

a mature lymphocyte to an antigen induces the lymphocyte to divide rapidly.
This proliferation of lymphocytes is called clonal selection.
Two types of clones are produced: short-lived activated effector cells (fight current battle) and long-lived memory cells… for future attacks by same pathogen.
Amplifying Lymphocytes by Clonal SelectionIn the body there are few lymphocytes with antigen receptors for any particular

Слайд 38Clonal Selection of B cells

B cells that
differ in
antigen


specificity
Antibody
molecules
Antigen
receptor
Antigen molecules
Clone of memory cells
Clone of plasma cells = effectors

Clonal Selection of B cells  B cells thatdiffer inantigen specificityAntibodymoleculesAntigenreceptorAntigen moleculesClone of memory cellsClone of plasma

Слайд 39The first exposure to a specific antigen represents the primary

immune response.
During this time, effector B cells = plasma

cells are generated, and T cells are activated to their effector forms.
In the secondary immune response = memory cells facilitate a faster, more efficient response.
The first exposure to a specific antigen represents the primary immune response. During this time, effector B

Слайд 40Antibodies
to A
Antibodies
to B
Secondary immune response to
antigen A produces antibodies to

A.
Primary immune response to antigen
B produces antibodies to B.
Primary immune

response
to antigen A produces
antibodies to A.

Antibody concentration
(arbitrary units)

Exposure
to antigen A

Exposure to
antigens A and B

Time (days)

104

103

102

101

100

0

7

14

21

28

35

42

49

56

Antibodiesto AAntibodiesto BSecondary immune response toantigen A produces antibodies to A.Primary immune response to antigenB produces antibodies

Слайд 41Acquired immunity defends against infection of body cells and fluids
Acquired

immunity has two branches: the humoral immune response and the

cell-mediated immune response.
Humoral immune response involves activation and clonal selection of B cells, resulting in production of secreted antibodies.
Cell-mediated immune response involves activation and clonal selection of cytotoxic T cells.
Helper T cells aid both responses.
Acquired immunity defends against infection of body cells and fluidsAcquired immunity has two branches: the humoral immune

Слайд 42 Acquired Immune Response
Humoral (antibody-mediated) immune response
B cell
Plasma cells
Cell-mediated immune response
Key
Stimulates
Gives

rise to
+
+
+
+
+
+
+
Memory B cells
Antigen (1st exposure)
Engulfed by
Antigen-
presenting cell
Memory
Helper T cells
Helper

T cell

Cytotoxic T cell

Memory
Cytotoxic T cells

Active
Cytotoxic T cells

Antigen (2nd exposure)

Secreted
antibodies

Defend against extracellular pathogens by binding to antigens,
thereby neutralizing pathogens or making them better targets
for phagocytes and complement proteins.

Defend against intracellular pathogens
and cancer by binding to and lysing the
infected cells or cancer cells.

+

+

+

Acquired Immune ResponseHumoral (antibody-mediated) immune response B cellPlasma cellsCell-mediated immune response KeyStimulatesGives rise

Слайд 43Acquired Immune Response
Key
Stimulates
Gives rise to
+
Memory
Helper T cells
Antigen-
presenting cell
Helper T cell
Engulfed

by
Antigen (1st exposure)
+
+
+
+
+
+
Defend against extracellular pathogens
Memory
B cells
Antigen (2nd exposure)
Plasma cells
B

cell

Secreted
antibodies

Humoral (antibody-mediated) immune response

Acquired Immune ResponseKeyStimulatesGives rise to+MemoryHelper T cellsAntigen-presenting cellHelper T cellEngulfed byAntigen (1st exposure)++++++Defend against extracellular pathogensMemoryB cellsAntigen

Слайд 44Acquired Immune Response
Cell-mediated immune response
Defend against intracellular pathogens
Active
Cytotoxic T cells
Memory
Cytotoxic

T cells
Memory
Helper T cells
Antigen-
presenting cell
Antigen (2nd exposure)
Helper T cell
Engulfed by
Antigen

(1st exposure)

Cytotoxic T cell

Key

Stimulates
Gives rise to

+

+

+

+

+

+

+

Acquired Immune ResponseCell-mediated immune responseDefend against intracellular pathogensActiveCytotoxic T cellsMemoryCytotoxic T cellsMemoryHelper T cellsAntigen-presenting cellAntigen (2nd exposure)Helper

Слайд 45 Helper T Cells: Respond to Nearly All Antigens
A surface

protein called CD4 binds the class II MHC molecule.
This binding

keeps the helper T cell joined to the antigen-presenting cell while activation occurs.
Activated helper T cells secrete cytokines that stimulate other lymphocytes.
Positive Feedback in the Immune System enhances the process until some endpoint or maximum rate is reached.
Helper T Cells: Respond to Nearly All AntigensA surface protein called CD4 binds the class II

Слайд 46The central role of helper T cells in humoral and

cell-mediated immune responses
Antigen-
presenting
cell
Peptide antigen
Cell-mediated
immunity
= attack on
infected cells.
Class II MHC

molecule

CD4

TCR (T cell receptor)

Helper T cell

Humoral
immunity
= secretion of
antibodies by
plasma cells.

Cytotoxic T cell

Cytokines
Positive Feedback …

B cell

Bacterium

+

+

+

+

The central role of helper T cells in humoral and cell-mediated immune responsesAntigen-presentingcellPeptide antigenCell-mediatedimmunity = attack oninfected

Слайд 47Cytotoxic T Cells: A Response to Infected Cells
Cytotoxic T cells

are the effector cells in cell-mediated immune response.
Cytotoxic T cells

make CD8, a surface protein that greatly enhances interaction between a target cell and a cytotoxic T cell.
Binding to a class I MHC complex on an infected cell activates a cytotoxic T cell and makes it an active killer.
The activated cytotoxic T cell secretes proteins that destroy the infected target cell.
Cytotoxic T Cells: A Response to Infected CellsCytotoxic T cells are the effector cells in cell-mediated immune

Слайд 48The killing action of cytotoxic T cells
Cytotoxic T cell

Perforin

Granzymes

TCR

CD8

Class I

MHC
molecule

Target
cell
Peptide
antigen
Pore

Released cytotoxic T cell
Dying target cell
1.
2.
3. lysis

The killing action of cytotoxic T cells Cytotoxic T cellPerforinGranzymesTCRCD8Class I MHCmoleculeTargetcellPeptideantigenPoreReleased cytotoxic T cellDying target cell1.2.3.

Слайд 49B Cells: A Response to Extracellular Pathogens
The humoral response is

characterized by secretion of antibodies by B cells.
Activation of B

cells is aided by cytokines and antigen binding to helper T cells.
Clonal selection of B cells generates antibody-secreting plasma cells, the effector cells of humoral immunity. Positive Feedback …
B Cells: A Response to Extracellular PathogensThe humoral response is characterized by secretion of antibodies by B

Слайд 50B cell activation in the humoral immune response
Antigen-presenting cell

Endoplasmic
reticulum of
plasma

cell

Secreted
antibody
molecules

Bacterium

B cell

Peptide
antigen

Class II MHC
molecule

TCR
CD4
Helper T cell
Activated
helper T cell
Cytokines
Clone of memory
B

cells

Clone of plasma cells

2 µm

+

B cell activation in the humoral immune response Antigen-presenting cellEndoplasmicreticulum ofplasma cellSecretedantibodymoleculesBacteriumB cellPeptideantigenClass II MHCmoleculeTCRCD4Helper T cellActivatedhelper

Слайд 51Antibody Classes
The five major classes of antibodies, or immunoglobulins, differ

in distribution and function.
Polyclonal antibodies are the products of many

different clones of B cells following exposure to a microbial antigen.
Monoclonal antibodies are prepared from a single clone of B cells grown in culture.
Antibody ClassesThe five major classes of antibodies, or immunoglobulins, differ in distribution and function.Polyclonal antibodies are the

Слайд 52The five antibody, or immunoglobulin (Ig), classes
Class of Immuno-
globulin (Antibody)
IgG
(monomer)
IgM
(pentamer)
J

chain
IgA
(dimer)
IgE
(monomer)
IgD
(monomer)
Trans-
membrane
region
J chain
Secretory
component
Distribution
Function
First Ig class
produced after
initial exposure to
antigen; then its
concentration in
the

blood declines

Promotes neutraliza-
tion and cross-
linking of antigens;
very effective in
complement system
activation

Present in
secretions such
as tears, saliva,
mucus, and
breast milk

Only Ig class that
crosses placenta,
thus conferring
passive immunity
on fetus

Triggers release from
mast cells and
basophils of hista-
mine and other
chemicals that cause
allergic reactions

Present primarily
on surface of
B cells that have
not been exposed
to antigens

Acts as antigen
receptor in the
antigen-stimulated
proliferation and
differentiation of
B cells (clonal
selection)

Most abundant Ig
class in blood;
also present in
tissue fluids

Promotes opsoniza-
tion, neutralization,
and cross-linking of
antigens; less effec-
tive in activation of
complement system
than IgM

Provides localized
defense of mucous
membranes by
cross-linking and
neutralization of
antigens

Presence in breast
milk confers
passive immunity
on nursing infant

Present in blood
at low concen-
trations

The five antibody, or immunoglobulin (Ig), classes Class of Immuno-globulin (Antibody)IgG(monomer)IgM(pentamer)J chainIgA(dimer)IgE(monomer)IgD(monomer)Trans-membraneregionJ chainSecretorycomponentDistributionFunctionFirst Ig classproduced afterinitial exposure

Слайд 53Distribution
Class of Immuno-
globulin (Antibody)
IgM
(pentamer)
J chain
First Ig class
produced after
initial exposure to
antigen;

then its
concentration in
the blood declines
Promotes neutraliza-
tion and cross-
linking of antigens;
very

effective in
complement system
activation

Function

DistributionClass of Immuno-globulin (Antibody)IgM(pentamer)J chainFirst Ig classproduced afterinitial exposure toantigen; then itsconcentration inthe blood declinesPromotes neutraliza-tion and

Слайд 54Distribution
Function
Class of Immuno-
globulin (Antibody)
IgG
(monomer)
Most abundant Ig
class in blood;
also present in
tissue

fluids
Promotes opsoniza-
tion, neutralization,
and cross-linking of
antigens; less effec-
tive in activation of
complement

system
than IgM

Only Ig class that
crosses placenta,
thus conferring
passive immunity
on fetus

DistributionFunctionClass of Immuno-globulin (Antibody)IgG(monomer)Most abundant Igclass in blood;also present intissue fluidsPromotes opsoniza-tion, neutralization,and cross-linking ofantigens; less effec-tive

Слайд 55Distribution
Function
Class of Immuno-
globulin (Antibody)
IgA
(dimer)
J chain
Secretory
component
Present in
secretions such
as tears, saliva,
mucus, and
breast

milk
Provides localized
defense of mucous
membranes by
cross-linking and
neutralization of
antigens
Presence in breast
milk confers
passive

immunity
on nursing infant
DistributionFunctionClass of Immuno-globulin (Antibody)IgA(dimer)J chainSecretorycomponentPresent insecretions suchas tears, saliva,mucus, andbreast milkProvides localizeddefense of mucousmembranes bycross-linking andneutralization ofantigensPresence

Слайд 56Distribution
Function
Class of Immuno-
globulin (Antibody)
IgE
(monomer)
Present in blood
at low concen-
trations
Triggers release from
mast

cells and
basophils of hista-
mine and other
chemicals that cause
allergic reactions

DistributionFunctionClass of Immuno-globulin (Antibody)IgE(monomer)Present in bloodat low concen-trationsTriggers release frommast cells andbasophils of hista-mine and otherchemicals that

Слайд 57Distribution
Function
Class of Immuno-
globulin (Antibody)
IgD
(monomer)
Trans-
membrane
region
Present primarily
on surface of
B cells that have
not

been exposed
to antigens
Acts as antigen
receptor in the
antigen-stimulated
proliferation and
differentiation of
B cells

(clonal
selection)
DistributionFunctionClass of Immuno-globulin (Antibody)IgD(monomer)Trans-membraneregionPresent primarilyon surface ofB cells that havenot been exposedto antigensActs as antigenreceptor in theantigen-stimulatedproliferation

Слайд 58The Role of Antibodies in Immunity
Neutralization occurs when a pathogen

can no longer infect a host because it is bound

to an antibody.
Opsonization occurs when antibodies bound to antigens increase phagocytosis.
Antibodies together with proteins of the complement system generate a membrane attack complex and cell lysis.

The Role of Antibodies in ImmunityNeutralization occurs when a pathogen can no longer infect a host because

Слайд 59Antibody-mediated mechanisms of antigen disposal
Viral neutralization
Virus
Opsonization
Bacterium
Macrophage
Activation of complement system
and

pore formation
Complement proteins
Formation of
membrane
attack complex
Flow of water
and ions
Pore
Foreign
cell

Antibody-mediated mechanisms of antigen disposal Viral neutralizationVirusOpsonizationBacteriumMacrophageActivation of complement system and pore formationComplement proteinsFormation ofmembraneattack complexFlow of

Слайд 60Active Immunization
Active immunity develops naturally in response to an infection.
It

can also develop following/ from immunization, also called vaccination.
In immunization,

a nonpathogenic form of a microbe or part of a microbe elicits an immune response to an immunological memory.
Active ImmunizationActive immunity develops naturally in response to an infection.It can also develop following/ from immunization, also

Слайд 61Passive immunity provides immediate, short-term protection.
It is conferred naturally when

IgG crosses the placenta from mother to fetus or when

IgA passes from mother to infant in breast milk.
It can also be conferred artificially by injecting antibodies into a nonimmune person.

Passive Immunity

Passive immunity provides immediate, short-term protection.It is conferred naturally when IgG crosses the placenta from mother to

Слайд 62Passive immunization of an infant occurs during breast-feeding

Passive immunization of an infant occurs during breast-feeding

Слайд 63Immune Rejection
Cells transferred from one person to another can be

attacked by immune defenses.
This complicates blood transfusions or the transplant

of tissues or organs.
MHC molecules are different among genetically nonidentical individuals.
Differences in MHC molecules stimulate rejection of tissue grafts and organ transplants.
Immune RejectionCells transferred from one person to another can be attacked by immune defenses.This complicates blood transfusions

Слайд 64Chances of successful transplantation increase if donor and recipient MHC

tissue types are well matched.
Immunosuppressive drugs facilitate transplantation.
Lymphocytes in bone

marrow transplants may cause the donor tissue to reject the recipient.
Chances of successful transplantation increase if donor and recipient MHC tissue types are well matched.Immunosuppressive drugs facilitate

Слайд 65Blood Groups
Antigens on red blood cells surface determine whether a

person has blood type A (A antigen), B (B antigen),

AB (both A and B antigens), or O (neither antigen).
Antibodies to nonself blood types exist in the body.
Transfusion with incompatible blood leads to destruction of the transfused cells.
Recipient-donor combinations can be fatal or safe.
Blood GroupsAntigens on red blood cells surface determine whether a person has blood type A (A antigen),

Слайд 66 Disruption in immune system function can elicit or exacerbate

disease
Some pathogens have evolved to diminish the effectiveness of host

immune responses.
If the delicate balance of the immune system is disrupted, effects range from minor to often fatal.


Disruption in immune system function can elicit or exacerbate diseaseSome pathogens have evolved to diminish the

Слайд 67Allergies
Allergies are exaggerated (hypersensitive) responses to antigens called allergens.
In localized

allergies such as hay fever, IgE antibodies produced after first

exposure to an allergen attach to receptors on mast cells.
AllergiesAllergies are exaggerated (hypersensitive) responses to antigens called allergens.In localized allergies such as hay fever, IgE antibodies

Слайд 68Mast cells, IgE, and the allergic response
Allergen
IgE
Granule
Mast cell
Histamine

Mast cells, IgE, and the allergic response AllergenIgEGranuleMast cellHistamine

Слайд 69The next time the allergen enters the body, it binds

to mast cell–associated IgE molecules.
Mast cells release histamine and other

mediators that cause vascular changes leading to typical allergy symptoms.
An acute allergic response can lead to anaphylactic shock, a life-threatening reaction that can occur within seconds of allergen exposure.
The next time the allergen enters the body, it binds to mast cell–associated IgE molecules.Mast cells release

Слайд 70Autoimmune Diseases
In individuals with autoimmune diseases, the immune system loses

tolerance for self and turns against certain molecules of the

body.
Autoimmune diseases include systemic lupus erythematosus, rheumatoid arthritis, insulin-dependent diabetes mellitus, and multiple sclerosis.
Autoimmune DiseasesIn individuals with autoimmune diseases, the immune system loses tolerance for self and turns against certain

Слайд 71X-ray of a hand deformed by rheumatoid arthritis

X-ray of a hand deformed by rheumatoid arthritis

Слайд 72Exertion, Stress, and the Immune System
Moderate exercise improves immune system

function.
Psychological stress has been shown to disrupt hormonal, nervous, and

immune systems.
Exertion, Stress, and the Immune SystemModerate exercise improves immune system function.Psychological stress has been shown to disrupt

Слайд 73Immunodeficiency Diseases
Inborn immunodeficiency results from hereditary or developmental defects that

prevent proper functioning of innate, humoral, and/or cell-mediated defenses.
Acquired immunodeficiency

results from exposure to chemical and biological agents.
Acquired immunodeficiency syndrome (AIDS) is caused by a virus.
Immunodeficiency DiseasesInborn immunodeficiency results from hereditary or developmental defects that prevent proper functioning of innate, humoral, and/or

Слайд 74Acquired Immune System Evasion by Pathogens
Pathogens have evolved mechanisms to

attack immune responses.
Through antigenic variation, some pathogens are able to

change epitope expression and prevent recognition.
The human influenza virus mutates rapidly, and new flu vaccines must be made each year.
Human viruses occasionally exchange genes with the viruses of domesticated animals.
This poses a danger as human immune systems are unable to recognize the new viral strain.

Acquired Immune System Evasion by PathogensPathogens have evolved mechanisms to attack immune responses.Through antigenic variation, some pathogens

Слайд 75Latency
Some viruses may remain in a host in an inactive

state called latency.
Herpes simplex viruses can be present in a

human host without causing symptoms.
LatencySome viruses may remain in a host in an inactive state called latency.Herpes simplex viruses can be

Слайд 76Attack on the Immune System: HIV
Human immunodeficiency virus (HIV) infects

helper T cells.
The loss of helper T cells impairs both

the humoral and cell-mediated immune responses and leads to AIDS.
HIV eludes the immune system because of antigenic variation and an ability to remain latent while integrated into host DNA.

Attack on the Immune System: HIVHuman immunodeficiency virus (HIV) infects helper T cells.The loss of helper T

Слайд 77The progress of an untreated HIV infection
Latency
Relative antibody
concentration
AIDS
Helper T cell

concentration
in blood (cells/mm3)
Helper T cell
concentration
Relative HIV
concentration
Years after untreated infection
0
1
2
3
4
5
6
7
8
9
10
0
200
400
600
800

The progress of an untreated HIV infection LatencyRelative antibodyconcentrationAIDSHelper T cell concentrationin blood (cells/mm3)Helper T cellconcentrationRelative HIVconcentrationYears

Слайд 78People with AIDS are highly susceptible to opportunistic infections and

cancers that take advantage of an immune system in collapse.


The spread of HIV is a worldwide problem.
The best approach for slowing this spread is education about practices that transmit the virus.
People with AIDS are highly susceptible to opportunistic infections and cancers that take advantage of an immune

Слайд 79Cancer and Immunity
The frequency of certain cancers increases when the

immune response is impaired.
Two suggested explanations are
Immune system normally suppresses

cancerous cells
Increased inflammation increases the risk of cancer
Cancer and ImmunityThe frequency of certain cancers increases when the immune response is impaired.Two suggested explanations areImmune

Слайд 80Review
Stem cell
Cell division and gene rearrangement
Antigen
Clonal selection
Elimination of
self-reactive
B cells
Formation of

activated cell populations
Antibody
Microbe
Memory cells
Effector B cells
Receptors bind to antigens

ReviewStem cellCell division and gene rearrangementAntigenClonal selectionElimination ofself-reactiveB cellsFormation of activated cell populationsAntibodyMicrobeMemory cellsEffector B cellsReceptors bind

Слайд 81You should now be able to:
Distinguish between innate and acquired

immunity.
Name and describe four types of phagocytic cells.
Describe the inflammation

response.
You should now be able to:Distinguish between innate and acquired immunity.Name and describe four types of phagocytic

Слайд 82Distinguish between the following pairs of terms: antigens and antibodies;

antigen and epitope; B lymphocytes and T lymphocytes; antibodies and

B cell receptors; primary and secondary immune responses; humoral and cell-mediated response; active and passive immunity.
Explain how B lymphocytes and T lymphocytes recognize specific antigens.
Explain why the antigen receptors of lymphocytes are tested for self-reactivity.
Distinguish between the following pairs of terms: antigens and antibodies; antigen and epitope; B lymphocytes and T

Слайд 83Describe clonal selection and distinguish between effector cells and memory

cells.
Describe the cellular basis for immunological memory.
Explain how a single

antigen can provoke a robust humoral response.
Compare the processes of neutralization and opsonization.
Describe clonal selection and distinguish between effector cells and memory cells.Describe the cellular basis for immunological memory.Explain

Слайд 84Describe the role of MHC in the rejection of tissue

transplants.
Describe an allergic reaction, including the roles of IgE, mast

cells, and histamine.
Describe some of the mechanisms that pathogens have evolved to thwart the immune response of their hosts.
List strategies that can reduce the risk of HIV transmission.
Describe the role of MHC in the rejection of tissue transplants.Describe an allergic reaction, including the roles

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