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Immunology
Chapter 14
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Normal Immune Response
• Immunity
• Is the body’s ability to resist disease
• Serves three functions
• Defense
• Homeostasis
• Surveillance
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Types of Immunity
• Innate
• Present at birth
• First-line defense against pathogens
• Acquired
• Developed immunity
• Active
• Passive
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Normal Immune Response
• Antigens
• Substances the body recognizes as
foreign that elicit an immune response
• Most are composed of protein.
• Antibodies
• Immune globulins produced by
lymphocytes in response to antigens
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Organs of Immunity
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Immune Response to Virus
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Normal Immune Response
Lymphoid Organs
• Central (primary) lymphoid organs
• Thymus gland
• Thymus gland shrinks with age.
• Involved in the differentiation and maturation
of T lymphocytes
• Bone marrow
• Produces red blood cells, white blood cells,
and platelets
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Normal Immune Response
Lymphoid Organs
• Peripheral lymphoid organs
• Lymph nodes
• Tonsils
• Spleen
• Lymphoid tissues associated with the gut,
genitals, bronchi, and skin
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Macrophages and Lymphocytes in
Immune Response
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10
Normal Immune System
Cells of Immune Response
• Mononuclear phagocytes
• Include monocytes in the blood and
macrophages found throughout the body
• Capture, process, and present antigens to
lymphocytes to initiate an immune
response
• Capture antigens by phagocytosis
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Normal Immune System
Cells of Immune Response
• Lymphocytes
• Produced in the bone marrow
• Eventually migrate to peripheral organs
• Differentiate into B and T lymphocytes
• T Cytotoxic cells
• T Helper cells
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Types of Lymphocytes
T cells
B cells
Natural killer (NK) cells
70%–80%
10%–20%
<10%
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Normal Immune Response
• Dendritic Cells
• Important in activating the immune
response
• Capture antigens at sites of contact with the
external environment
• Transport an antigen until it encounters a T
cell with specificity for the antigen
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Normal Immune Response
• Cytokines
• Soluble factors secreted by WBCs and a
variety of other cells in the body
• Act as messengers among cell types
• Instruct cells to alter their proliferation,
differentiation, secretion, or activity
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Normal Immune Response
• Cytokines
• Currently at least 100 different cytokines
• Have a beneficial role in hematopoiesis
and immune function
• Can have detrimental effects
• Chronic inflammation
• Autoimmune diseases
• Sepsis
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Normal Immune Response
• Cytokine types
• Interleukins
• Interferons
• Tumor necrosis factor
• Colony-stimulating factors
• Erythropoietin
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Normal Immune Response
Cytokines
• IL-1
• Augments immune response
• Inflammatory mediator
• Promotes maturation and clonal
expansion of B cells
• Enhances activity of natural killer cells
• Activates T cells and macrophages
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Normal Immune Response
Cytokines
• IL-2
• Induces proliferation and differentiation
of T cells
• Activates T cells, NK cells, and
macrophages
• Stimulates release of other cytokines
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Normal Immune Response
Cytokines
• IL-3 (multicolony-stimulating factor)
• Hematopoietic growth factor for
hematopoietic precursor cells
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Normal Immune Response
Cytokines
• IL-4
• B-cell growth factor
• Stimulates proliferation and
differentiation of B cells
• Induces differentiation into TH2 cells
• Stimulates growth of mast cells
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Normal Immune Response
Cytokines
• IL-5
• B-cell growth and differentiation
• Promotes growth and differentiation of
eosinophils
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Normal Immune Response
Cytokines
• IL-6
• T- and B-cell growth factor
• Enhances inflammatory response
• Stimulates antibody secretion
• Promotes differentiation of B cells into
plasma cells
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Normal Immune Response
Cytokines
• IL-6
• Induces fever
• Synergistic effects with IL-1 and TNF
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Normal Immune Response
Cytokines
• -Interferon (-IFN) and β-interferon
(β-INF)
• Inhibit viral replication
• Activate NK cells and macrophages
• Antiproliferative effects on tumor cells
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Normal Immune Response
Cytokines
• γ-Interferon (γ-IFN)
• Activates macrophages, neutrophils, and
NK cells
• Promotes B-cell differentiation
• Inhibits viral replication
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Mechanism of Action of Interferon
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Normal Immune Response
Cytokines
• Tumor necrosis factor (TNF)
• Activates macrophages and granulocytes
• Promotes the immune and inflammatory
responses
• Kills tumor cells
• Responsible for extensive weight loss
• Associated with chronic inflammation and
cancer
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Normal Immune Response
Cytokines
• Colony-stimulating factors (CSFs)
• Granulocyte colony-stimulating factor (GCSF)
• Granulocyte-macrophage colonystimulating factor (GM-CSF)
• Macrophage colony-stimulating factor (MCSF)
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Normal Immune Response
Comparison of
Humoral and Cell-Mediated Immunity
Humoral
Cells involved B lymphocytes
Products
Antibodies
Memory cells
Present
Cellular
• T lymphocytes
• Macrophages
• Sensitized T cells
• Cytokines
Present
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30
Normal Immune Response
Comparison of
Humoral and Cell-Mediated Immunity
Humoral
Protection • Bacteria
• Viruses
(extracellular)
• Respiratory
pathogens
• Gastrointestinal
pathogens
Cellular
• Fungus
• Viruses
(intracellular)
• Chronic infectious
agents
• Tumor cells
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31
Normal Immune Response
Humoral Immunity
• Antibody-mediated immunity
• Antibodies produced by plasma cells
(differentiated B lymphocytes)
• Primary immune response is evident
4 to 8 days after initial exposure to
antigen.
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Normal Immune Response
Humoral Immunity
• Five classes of immune globulins
• Each has specific characteristics
• IgG
• lgA
• lgM
• lgD
• lgE
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Normal Immune Response
Humoral Immunity
• When an individual is exposed to an
antigen for a second time, the
response is faster (1 to 3 days) and
lasts longer.
• Main product of secondary response is IgG
rather than IgM.
• Memory cells account for more rapid
production of IgG.
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Primary and Secondary Immune
Response
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Normal Immune Response
Cell-Mediated Immunity
• Immune responses initiated through
specific antigen recognition by T cells
• Several cell types involved in cellmediated immunity
• T lymphocytes
• Macrophages
• NK cells
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Normal Immune Response
Cell-Mediated Immunity
• Important roles
• Immunity against pathogens that survive
inside cells (viruses, some bacteria)
• Fungal infections
• Rejection of transplanted tissues
• Contact hypersensitivity reactions
• Tumor immunity
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Effects of Aging on the
Immune System
• Immunosenescence
• ↑ Incidences of tumors
• Greater susceptibility to infection
• ↑ Autoantibodies
• ↓ Cell-mediated immunity
• Thymic involution
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Effects of Aging on the
Immune System
• Immunosenescence
• ↓ Delayed hypersensitivity reaction
• ↓ IL-1 and IL-2 synthesis
• ↓ Expression of IL-2 receptors
• ↓ Proliferation response of T and B cells
• ↓ Primary and secondary antibody
responses
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Audience Response Question
A patient with a sore throat and rhinitis has an
elevated level of IgG in the blood. The nurse explains
that the patient’s symptoms are most likely caused by
a.
b.
c.
d.
an allergy.
exposure to toxic fume.
an initial viral infection.
a re-infection by bacteria.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.