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Lecture 12 – Animal Immune Systems

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Title: Lecture 12 – Animal Immune Systems


1
Lecture 12 Animal Immune Systems
2
Key Concepts
  • Innate immunity provides broad-spectrum defense
    against many pathogens
  • Acquired immunity is very specific, develops over
    time, and relies on B and T cells
  • Antigen recognition properties of B and T cells
  • B and T cell binding sites develop randomly!
  • Integrated B and T cell function
  • When the immune system goes wrong

3
Some definitions.
Generates Pathology
  • Pathogen anything that causes disease
  • Microbes (bacteria, protozoans), viruses, fungal
    spores, pollen, dust mites, etc
  • Secretions (venoms, animal saliva)
  • Non-self tissue cells (transplant rejections)
  • Some cancer cells
  • Antigens cell surface proteins and other
    molecules that the body recognizes as non-self

Generates Antibodies
Pathogens have Antigens
4
The immune system is spread diffusely throughout
the body a system of organs, nodes and lymph
vessels
Schematic of the human immune system
5
Remember, the white blood cells are the defenders
Diagram of the blood cells
6
Some WBCs circulate though the lymph, the blood
and the interstitial fluidSome are permanently
housed in lymph nodes, thymus gland, spleen,
appendix and a few other glands
7
Defense is step-wise
  • 90 of pathogens are neutralized by innate
    immunity
  • Multiple strategies to destroy pathogens
  • Any remaining pathogens are normally attacked by
    the acquired immune system

Table showing the stages of defense
8
Innate Immunity you are born with it
  • Pathogens are ubiquitous
  • Innate immunity includes both external and
    internal systems to eliminate pathogens
  • Any and all pathogens are targeted
  • This system does not recognize specific pathogens
    it goes after any non-self cell

9
Innate Immunity external defenses
  • Skin important barrier, acids
  • Mucous membranes trap, cilia evacuate
  • Secretions both skin and mucous secrete
    anti-microbial proteins stomach secretes acids

Sweeping cilia in trachea
10
Innate Immunity internal defenses
  • Sometimes pathogens get past the barriers and
    into the tissues
  • Non-specific WBCs attack
  • Neutrophils
  • Monocytes ? macrophages
  • Dendritic cells
  • Eosinophils
  • Basophils

11
Innate Immunity internal defenses
  • Phagocytic WBCs cells ingest and destroy
    microbes in the tissues
  • Neutrophils the most abundant, but short-lived
  • Macrophages develop from monocytes large and
    long-lived
  • Dendritic cells mostly function to stimulate
    the acquired immune system

12
Model of a macrophage ingesting a fungal spore
13
Micrograph of macrophage ingesting bacteria
14
Innate Immunity internal defenses
  • Eosinophils destroy multi-cellular parasites by
    releasing toxic enzymes
  • Also contribute to allergic responses
  • Basophils contribute to inflammatory and allergic
    responses

Schistosoma mansoni
15
Additional Internal Defenses
  • Antimicrobial proteins
  • Lysosymes work in macrophages also found in
    saliva, tears and mucous
  • Complement proteins result in lysis also help
    trigger inflammation and activate acquired
    immunity
  • Interferons limit intra-cellular spread of
    viruses
  • Defensins are secreted by macrophages, attack
    pathogens
  • Natural killer cells attack virus-infected cells
    and cancer cells
  • The inflammatory response

16
Complement Protein Functionthese proteins
complement other immune system processes
Diagram showing complement protein function
17
Additional Internal Defenses
  • Antimicrobial proteins
  • Lysosymes work in macrophages also found in
    saliva, tears and mucous
  • Complement proteins result in lysis also help
    trigger inflammation and activate acquired
    immunity
  • Interferons limit intra-cellular spread of
    viruses
  • Defensins are secreted by macrophages, attack
    pathogens
  • Natural killer cells attack virus-infected cells
    and cancer cells
  • The inflammatory response

18
Interferons initiate production of proteins that
inhibit viral reproduction
Diagram of interferon activity
19
Additional Internal Defenses
  • Antimicrobial proteins
  • Lysosymes work in macrophages also found in
    saliva, tears and mucous
  • Complement proteins result in lysis also help
    trigger inflammation and activate acquired
    immunity
  • Interferons limit intra-cellular spread of
    viruses
  • Defensins are secreted by macrophages, attack
    pathogens
  • Natural killer cells attack virus-infected cells
    and cancer cells
  • The inflammatory response

20
Additional Internal Defenses
  • Antimicrobial proteins
  • Lysosymes work in macrophages also found in
    saliva, tears and mucous
  • Complement proteins result in lysis also help
    trigger inflammation and activate acquired
    immunity
  • Interferons limit intra-cellular spread of
    viruses
  • Defensins are secreted by macrophages, attack
    pathogens
  • Natural killer cells attack virus-infected cells
    and cancer cells
  • The inflammatory response

21
A natural killer cell (yellow) attacking a cancer
cell (red).
22
Additional Internal Defenses
  • Antimicrobial proteins
  • Lysosymes work in macrophages also found in
    saliva, tears and mucous
  • Complement proteins result in lysis also help
    trigger inflammation and activate acquired
    immunity
  • Interferons limit intra-cellular spread of
    viruses
  • Defensins are secreted by macrophages, attack
    pathogens
  • Natural killer cells attack virus-infected cells
    and cancer cells
  • The inflammatory response

23
The Inflammatory Response
  • Usually localized, in response to tissue injury
  • Cascade of events
  • May also be systemic increased WBC release from
    bone marrow fever

Diagram of the inflammatory response
24
Invertebrates Also Have InnateDefense Systems
  • Amoeboid cells ingest by phagocytosis in
    echinoderms
  • Insect exoskeleton acts as a barrier similar to
    skin
  • Hemocytes in insect hemolymph function similarly
    to vertebrate innate internal defenses
  • Research indicates little immune system memory
  • Little capacity for acquired immunity as seen in
    vertebrates

25
Defense is step-wise
  • 90 of pathogens are neutralized by innate
    immunity both external and internal
  • Any remaining pathogens are normally attacked by
    the acquired immune system

26
Acquired Immunity
  • Develops over time, in response to exposure to
    pathogens
  • Highly specific lymphocytes develop that match
    each incoming pathogen
  • B cells and T cells
  • Circulate in tissues some are also permanently
    located in lymph nodes, the spleen and other
    lymph system structures
  • Pathogen contact with lymphocytes, phagocytes,
    and other triggers initiates rapid immune
    responses

27
Remember the lymph system is closely tied to
the circulatory system
  • Lymph vessels absorb excess fluids in capillary
    beds
  • Pathogens in the blood are rapidly exposed to the
    phagocytes and lymphocytes in the lymph system
  • Every heart beat pushes blood, and any pathogens
    it carries, past the immune system structures

28
The next 3 slides show the relationship between
the capillary beds and the lymph vessels
29
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30
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31
Remember the lymph system is closely tied to
the circulatory system
  • Lymph vessels absorb excess fluids in capillary
    beds
  • Pathogens in the blood are rapidly exposed to the
    phagocytes and lymphocytes in the lymph system
  • Every heart beat pushes blood, and any pathogens
    it carries, past the immune system structures

32
Antigen Recognition
  • Remember, antigens are the non-self molecules
    that initiate the immune response
  • Mostly cell surface proteins, other cell surface
    molecules, or toxins dissolved in fluid (venoms
    and other secretions)
  • Most pathogens have several different kinds of
    antigens
  • Because of this, there are usually several
    different lymphocytes that recognize and respond
    to the pathogen
  • Antigens have specific binding sites epitopes

33
Membranes are complex, with many surface molecules
Diagram showing structure of the cell membrane
34
Antigen Recognition
  • Remember, antigens are the non-self molecules
    that initiate the immune response
  • Mostly cell surface proteins, other cell surface
    molecules, or toxins dissolved in fluid (venoms
    and other secretions)
  • Most pathogens have several different kinds of
    antigens
  • Because of this, there are usually several
    different lymphocytes that recognize and respond
    to the pathogen
  • Antigens have specific binding sites epitopes

35
Epitopes are the specific binding sites found on
all antigens
Diagram showing epitope structure
36
Lymphocytes B and T Cells
  • Remember, lymphocytes are one of the categories
    of white blood cells
  • Each B or T cell has 100,000 antigen receptors
    all of the exact same type
  • Each B or T cell recognizes a single epitope
  • The receptor molecules and recognition process
    are different for B cells vs. T cells
  • Both types of receptors are protein-based
  • Both have both constant and variable regions

37
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38
Lymphocytes B and T Cells
  • Remember, lymphocytes are one of the categories
    of white blood cells
  • Each B or T cell has 100,000 antigen receptors
    all of the exact same type
  • Each B or T cell recognizes a single epitope
  • The receptor molecules and recognition process
    are different for B cells vs. T cells
  • Both types of receptors are protein-based
  • Both have both constant and variable regions

39
Constant regions have stable amino acid sequences
from cell to cellVariable regions have
different amino acid sequences from cell to cell
Diagram showing the receptor molecules in B cells
and T cells. This diagram is used several times
in the next sequence of slides.
40
Antigen Recognition B Cells
  • B cell receptors are Y-shaped
  • Each branch of the Y has 2 parts, called chains
  • Inner, heavy chain makes the full Y
  • Outer, light chain is located on the branches of
    the Y
  • Both chains are proteins
  • Chains are linked by chemical bonds
  • The bottom of the Y is anchored in the B cell
    membrane

41
B Cell Receptor Structure
42
The protein structure of a B cell receptor
43
Antigen Recognition B Cells
  • The bottom regions of both chains have constant
    amino acid sequences
  • The outer branches of both chains, have variable
    amino acid sequences
  • These variable ends are the antigen binding sites
  • They bind directly to the epitopes
  • B cells recognize unaltered antigens!

44
B Cell Receptor Structure
45
Antigen Recognition T Cells
  • T cell receptors are unbranched
  • a chain and ß chain are chemically linked
  • Both are anchored in the membrane
  • Both have basal constant regions and terminal
    variable regions
  • A single antigen binding site is at the terminus

46
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47
T Cells DO NOT recognize intact antigens on
intact pathogens
  • T cells recognize antigen fragments that have
    been bound to a self-cell protein called an MHC
    molecule
  • MHC ? major histocompatibility complex of genes
    codes for these molecules
  • MHC molecules bind to antigen fragments inside a
    self-cell, and present the fragments at the
    surface of the cell
  • T cells detect the presented antigenMHC complex

48
MHC self-cell proteins
Diagram showing the production of MHC molecules,
how they become attached to antigen fragments,
and how the complex is presented at the cell
surface. This diagram is used repeatedly in the
next sequence of slides.
49
T Cells DO NOT recognize intact antigens on
intact pathogens
  • T cells recognize antigen fragments that have
    been bound to a self-cell protein called an MHC
    molecule
  • MHC ? major histocompatibility complex of genes
    codes for these molecules
  • MHC molecules bind to antigen fragments inside a
    self-cell, and present the fragments at the
    surface of the cell
  • T cells detect the presented antigenMHC complex

50
Development of MHC Variation
  • MHC alleles are numerous
  • Many more than just the 2 alleles common for most
    genes (ie not just dominant vs. recessive)
  • As a result, MHC molecules are the most
    polymorphic proteins known
  • Almost all antigens are recognized
  • Also, because of the high degree of variation, it
    is very rare for any two individuals to have the
    exact same set of MHC molecules
  • MHC molecules are unique to the self
  • Help to distinguish self from non-self cells

51
Development of MHC Variation
  • MHC alleles are numerous
  • Many more than just the 2 alleles common for most
    genes (ie not just dominant vs. recessive)
  • As a result, MHC molecules are the most
    polymorphic proteins known
  • Almost all antigens are recognized
  • Also, because of the high degree of variation, it
    is very rare for any two individuals to have the
    exact same set of MHC molecules
  • MHC molecules are unique to the self
  • Help to distinguish self from non-self cells

52
T Cells DO NOT recognize intact antigens on
intact pathogens
  • T cells recognize antigen fragments that have
    been bound to a self-cell protein called an MHC
    molecule
  • MHC ? major histocompatibility complex of genes
    codes for these molecules
  • MHC molecules bind to antigen fragments inside a
    self-cell, and present the fragments at the
    surface of the cell
  • T cells detect the presented antigenMHC complex

53
Two classes of MHC molecules each found in a
different type of antigen presenting cell
54
Class I MHC
  • Found in most nucleated cells
  • They bind antigen fragments if the cell has been
    infected, or is cancerous
  • Class I MHCantigen complexes are recognized by
    cytotoxic T cells
  • Cytotoxic T cells then destroy the infected or
    cancerous cell

55
Antigen Presentation Class I MHC molecules are
presented on infected or cancerous cells
56
Class II MHC
  • Found in dendritic cells, macrophages and B cells
  • Present antigens from pathogens that have been
    engulfed by phagocytosis
  • Class II MHCantigen complexes are recognized by
    helper T cells
  • Activated helper T cells begin a cascade of
    events that control the infection

57
Antigen Presentation Class II MHC molecules are
presented on phagocytic cells
58
In both cases, the T cell recognizes ONLY THE
COMBINATION of antigen self-protein
59
Review B and T Cell Receptors
B cell receptors bind directly to antigen on
intact pathogen
T cell receptors bind to MHCantigen complex on
self-cells
60
Review B and T Cell Receptors
Remember both B and T cells have multiple
receptors per cell (as many as 100,000), all
identical
61
Key Concepts
  • Innate immunity provides broad-spectrum defense
    against many pathogens
  • Acquired immunity is very specific, develops over
    time, and relies on B and T cells
  • Antigen recognition properties of B and T cells
  • B and T cell binding sites develop randomly!
  • Integrated B and T cell function
  • When the immune system goes wrong

62
Lymphocyte (B T cell) Development
  • Lymphocytes are all produced from stem cells in
    the bone marrow
  • Some mature in the bone marrow (B cells)
  • The rest mature in the thymus gland (T cells)

63
Lymphocyte (B T cell) Development
  • Maturation development of the B and T cell
    receptors
  • Once the cells are fully differentiated, they
    migrate into the rest of the body
  • Some stay permanently in the organs of the lymph
    system
  • Some circulate constantly through blood, lymph
    and interstitial fluids

64
Lymphocyte (B T cell) Development
  • Step 1 generation of diversity
  • Step 2 testing and removal
  • Step 3 clonal selection
  • Steps 1 and 2 occur during the development of the
    B and T cells
  • Step 3 occurs after exposure of the fully
    developed B and T cells to antigens

65
Lymphocyte (B T cell) DevelopmentStep 1
generation of diversity
  • The genes that code for the antigen receptors are
    randomly rearranged by enzymes during lymphocyte
    maturation
  • These are the genes that code for the variable
    regions of the light and heavy chains of B cells
  • Ditto for the variable regions of the a and ß
    chains of T cells
  • These chains are then linked together to form the
    T cell receptor molecule

66
Example gene re-alignment for the light chain
of a B cell receptor.
Diagram showing the development of diversity in
the receptors of a B cell. This diagram is used
repeatedly in the next sequence of slides.
67
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68
The coding gene has 40 variable (V) segments and
5 joining (J) segments
69
During differentiation of each B cell, one V
segment is snipped out and attached to one J
segment. Recombinase enzymes randomly snip and
join!
70
40 V regions x 5 J regions 200 possible
combinations of V and J in the functional gene.
Each cell ends up with only one of these possible
combinations for the light chain.
71
The VJ segment is attached via an intron to the
C segment that codes for the constant region of
the light chain.
72
This new gene is processed and translated into
the protein that makes up the light chain
73
The DNA coding for the heavy chain goes through
the same kind of random rearrangement process,
but there are more V regions
74
The light and heavy chains form independently
and are then linked thus the enormous number of
possible receptors Up to 1 million different
receptors are produced in B cells!!!
75
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76
Lymphocyte (B T cell) DevelopmentStep 1
generation of diversity
  • The genes that code for the antigen receptors are
    randomly rearranged by enzymes during lymphocyte
    maturation
  • These are the genes that code for the variable
    regions of the light and heavy chains of B cells
  • Ditto for the variable regions of the a and ß
    chains of T cells
  • These chains are then linked together to form the
    T cell receptor molecule

77
Lymphocyte (B T cell) DevelopmentStep 2
testing and removal
  • The rearrangement process is entirely random
  • Each new receptor is tested against self-cells
    both during development and during migration
    into lymph system organs
  • Receptors that bind to self-cells or self-MHC
    molecules are eliminated or deactivated

78
Critical Thinking
  • Why would testing be so important???

79
Critical Thinking
  • Why would testing be so important???
  • Testing process ensures that the immune system
    can distinguish self from non-self

80
Differentiation and testing result in an enormous
variety of B and T cells each capable of
recognizing a single epitope
  • 1 million different B cells
  • 10 million different T cells
  • Usually no duplication you start out with a
    single cell of each type
  • Clonal selection (the next step) builds a
    population of duplicate lymphocytes

81
Lymphocyte (B T cell) DevelopmentStep 3
clonal selection
  • Each B and T cell has receptors that are specific
    to a single epitope
  • Incoming pathogens typically display several
    epitopes
  • Virtually always, there is a B or T cell receptor
    to match at least one of the pathogen epitopes

82
Critical Thinking
  • How are incoming pathogens exposed to these
    myriad B and T cells???

83
Critical Thinking
  • How are incoming pathogens exposed to these
    myriad B and T cells???
  • Remember the way blood and lymph circulate
  • Incoming pathogens are rapidly exposed to the B
    and T cells because of the leaky capillaries and
    the lymph vacuum system

84
Lymphocyte (B T cell) DevelopmentStep 3
clonal selection
  • When a lymphocyte receptor encounters a matching
    epitope, the lymphocyte is activated
  • Activation stimulation of the lymphocyte to
    begin mitotic cloning

Diagram showing clonal expansion of selected B
cell
85
Lymphocyte (B T cell) DevelopmentStep 3
clonal selection
  • Duplicate lymphocytes are rapidly produced
  • Two clonal populations form
  • Effector cells are short-lived and carry out the
    immune system response (varies based on type of
    lymphocyte more later)
  • Memory cells are long-lived and remember the
    epitope
  • Memory cells allow for rapid response to that
    same pathogen the next time it enters the body
  • Memory cells confer active immunity

86
Clones divide into two populations effector and
memory
Diagram showing clonal expansion of selected B
cell
87
Lymphocyte (B T cell) DevelopmentStep 3
clonal selection
  • Duplicate lymphocytes are rapidly produced
  • Two clonal populations form
  • Effector cells are short-lived and carry out the
    immune system response (varies based on type of
    lymphocyte more later)
  • Memory cells are long-lived and remember the
    epitope
  • Memory cells allow for rapid response to that
    same pathogen the next time it enters the body
  • Memory cells confer active immunity

88
Step 3 clonal selectionMemory cells accumulate
over repeated exposure to the same pathogen
EX is for B cells T cells also accumulate
Graph showing accumulation of memory cells after
repeated exposures.
89
Critical thinking
  • If the immune system response is so rapidly
    initiated, why do we ever get sick???

90
Critical thinking
  • If the immune system response is so rapidly
    initiated, why do we ever get sick???
  • Note that the initial response takes about 2
    weeks to peak
  • This is about how long we usually stay sick after
    first exposure to a new pathogen!
  • Future exposures are more rapidly attacked

91
Key Concepts
  • Innate immunity provides broad-spectrum defense
    against many pathogens
  • Acquired immunity is very specific, develops over
    time, and relies on B and T cells
  • Antigen recognition properties of B and T cells
  • B and T cell binding sites develop randomly!
  • Integrated B and T cell function
  • When the immune system goes wrong

92
Integrated B and T Cell Function
Diagram showing how B cell and T cell functions
are integrated
93
Simultaneous
94
Helper T Cell Function
  • Nearly all antigens activate helper T cells
  • Dendritic phagocytes 1o activate naïve helper T
    cells
  • Important in primary immune response
  • Macrophages 1o activate memory helper T cells
  • Important in secondary immune response

Diagram of helper T cell binding to antigen
presenting cell.
95
Helper T Cell Function
  • Clones of active and memory T cells develop after
    exposure
  • Active helper T cells secrete proteins that
    stimulate cytotoxic T cells and B cells

96
Active helper T cells stimulate the rest of the
immune systemboth cytotoxic T cells and B cells
Diagram showing activated helper T cell functions.
97
Cytotoxic T Cell Function
  • Activated cytotoxic T cells release proteins that
    perforate target cells initiate apoptosis
  • The activated T cell releases, and moves on to
    target additional infected or cancer cells

Diagram showing cytotoxic T cell function
98
B Cell Function
  • Remember, B cells recognize and bind to specific
    intact pathogens
  • B cells also engulf some pathogens by
    phagocytosis
  • Antigens are presented on the B cell surface
  • These antigens are recognized by helper T cells
  • Helper T cells activate the B cell
  • Only its one specific antigen can be presented by
    each type of B cell

99
Some B cells are activated directly by exposure
to the antigen
100
B Cell Function
  • Remember, B cells recognize and bind to specific
    intact pathogens
  • B cells also engulf some pathogens by
    phagocytosis
  • Antigens are presented on the B cell surface
  • These antigens are recognized by helper T cells
  • Helper T cells activate the B cell
  • Only its one specific antigen can be presented by
    each type of B cell

101
Most B cells are activated by proteins secreted
from active helper T cells
Diagram showing an activated helper T activating
a B cell
102
B Cell Function
  • Remember, B cells recognize and bind to specific
    intact pathogens
  • B cells also engulf some pathogens by
    phagocytosis
  • Antigens are presented on the B cell surface
  • These antigens are recognized by helper T cells
  • Helper T cells activate the B cell
  • Only its one specific antigen can be presented by
    each type of B cell

103
B Cell Function
  • Activated B cells form 2 clones plasma cells
    and memory cells
  • Plasma cells release antibodies

Diagram showing secretion of antibodies from
activated B cell
104
Antibodies
  • Each activated B cells produces thousands of
    clones
  • Each clonal B cell releases nearly a billion
    antibodies
  • 2000 antibodies per second
  • Each B cell has a 4 5 day life span

Table of antibodies and their functions
105
Antibodies
  • Five classes of antibodies are secreted
  • Each recognizes and attacks specific pathogens
  • Read through this table for understanding dont
    memorize

106
Antibodies
  • Only one antibody per type of B cell
  • But remember, most pathogens have multiple
    antigens with multiple epitopes
  • Many B cells are activated

107
Antibody Mediated Pathogen Disposal
Diagram showing how antibodies work
108
Integrated B and T Cell Function
  • Responses to pathogens are coordinated and
    simultaneous, NOT mutually exclusive
  • All components of the immune system are activated
  • Positive feedback increases function

109
Active vs. Passive Immunity
  • Active immunity is generated when the acquired
    immune system is activated
  • Memory cells are generated
  • Exposure to pathogen OR vaccination with
    inactivated pathogen that still retains antigens
  • Confers long-term protection (often, lifetime)
  • Passive immunity is generated when antibodies
    alone are transferred
  • Does not generate memory cells
  • Antibodies cross placenta are injected
  • Short-term protection

110
Critical Thinking
  • What would be the advantage of passive immunity???

111
Critical Thinking
  • What would be the advantage of passive
    immunity???
  • Rapid protection against very toxic pathogens
    rabies virus, snake venoms

112
Key Concepts
  • Innate immunity provides broad-spectrum defense
    against many pathogens
  • Acquired immunity is very specific, develops over
    time, and relies on B and T cells
  • Antigen recognition properties of B and T cells
  • B and T cell binding sites develop randomly!
  • Integrated B and T cell function
  • When the immune system goes wrong

113
Immune System Failure
  • Allergic responses
  • Hypersensitive response to allergenic antigens
  • Antibody tails bind to mast cells
  • Exposure causes massive histamine release
  • Autoimmune diseases
  • Immune system fails to distinguish self-cells
  • Immunodeficiency diseases
  • Immune system fails
  • Can be genetic, developmental, or acquired
  • AIDS also some cancers, chemotherapy, stress

114
Allergic Responses
  • Most generated by IgE antibodies
  • Antibody tail binds to mast cells
  • IgE accumulates on mast cell surface
  • Eventually, allergen binds between 2 IgE
  • This triggers massive release of histamine
  • Histamine dilates blood vessels..

115
Immune System Failure
  • Allergic responses
  • Hypersensitive response to allergenic antigens
  • Antibody tails bind to mast cells
  • Exposure causes massive histamine release
  • Autoimmune diseases
  • Immune system fails to distinguish self-cells
  • Immunodeficiency diseases
  • Immune system fails
  • Can be genetic, developmental, or acquired
  • AIDS also some cancers, chemotherapy, stress

116
Rheumatoid Arthritis
117
Diabetes
118
Multiple Sclerosis
119
Lupus
120
Immune System Failure
  • Allergic responses
  • Hypersensitive response to allergenic antigens
  • Antibody tails bind to mast cells
  • Exposure causes massive histamine release
  • Autoimmune diseases
  • Immune system fails to distinguish self-cells
  • Immunodeficiency diseases
  • Immune system fails
  • Can be genetic, developmental, or acquired
  • AIDS also some cancers, chemotherapy, stress

121
T Cell
HIV
122
2007 40 million people are infected by HIV 15
million children have been orphaned by AIDS
Graph showing relationship between HIV
concentration, antibody concentration and T cell
concentration over time.
123
REVIEW Key Concepts
  • Innate immunity provides broad-spectrum defense
    against many pathogens
  • Acquired immunity is very specific, develops over
    time, and relies on B and T cells
  • Antigen recognition properties of B and T cells
  • B and T cell binding sites develop randomly!
  • Integrated B and T cell function
  • When the immune system goes wrong
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