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THIRD EDITION
HUMAN PHYSIOLOGY
AN INTEGRATED APPROACH
Dee Unglaub Silverthorn, Ph.D.
Chapter 24
The Immune System
PowerPoint® Lecture Slide Presentation by
Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University
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About this Chapter
• Anatomy & function of immune system, organs, &
cells
• How the body defends itself
• Non-specific body defenses
• Specific defenses that target one pathogen
• Combined defenses against bacteria and viruses
• Allergies and autoimmune problems
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Immune System Functions: Overview of Defenses
• Scavenge dead, dying or abnormal (cancerous)
body cells
• Protect from pathogens & foreign molecules
• Parasites
• Bacteria
• Viruses
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Immune System Functions: Overview of Defenses
Figure 24-1: Viruses
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HIV or Human Immunodeficiency Virus
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Life Cycle
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Infectious Causes of Gastroenteritis.
Bok K, Green KY. N Engl J Med 2012;367:2126-2132.
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Genomic Organization and Atomic Structure of the Norovirus Capsid.
Bok K, Green KY. N Engl J Med 2012;367:2126-2132.
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Body Defenses: Overview
• Physical barriers: skin & epithelial linings & cilia
• Chemical: acids, mucous & lysozymes
• Immune defenses – internal
• Innate, non-specific, immediate response
(min/hrs)
• Acquired – attack a specific pathogen (antigen)
• Steps in Immune defense
• Detect invader/foreign cells
• Communicate alarm & recruit immune cells
• Suppress or destroy invader
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Lymphatic System:
Overview of Immune Defense Organs & Cells
• Bone marrow
• Thymus
• Lymph nodes
• Spleen
• Lymph vessels
• Leukocytes:
• (white blood cells – WBCs)
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Lymphatic System:
Overview of Immune Defense Organs & Cells
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Figure 24-2 ab: Anatomy of the immune system
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Key Cells & Overview of their Function in Immune
Defense
• Lymphocytes: helper, plasma, cytotoxic & natural
killer (NK)
• Basophils
• Mast cells
• Monocytes
• Macrophages
• Neutrophils
• Eosinophils
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Key Cells & Overview of their Function in Immune
Defense
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Figure 24-4: Cells of the immune system
Innate Immunity: Phagocytosis & Inflammation
• Physical & chemical barriers
• Phagocytosis: macrophages, neutrophils, NK cells
• Engulf and digest recognized "foreign" cells –
molecules
• Inflammatory response
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Innate Immunity: Phagocytosis & Inflammation
Figure 24-6: Phagocytosis
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Cells of the Innate Immune System
The Innate Leukocytes include:
• Natural killer cells
• Mast cells
• Eosinophils
• Basophils
• Phagocytic cells: including macrophages,
neutrophils and dendritic cells, and
All these cells function within the immune system by identifying and
eliminating pathogens that might cause infection
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Chemical factors produced during inflammation
• Histamine
• Bradykinin
• Serotonin
• Leukotrienes
sensitize pain receptors, cause vasodilation of the
blood vessels at the scene, and attract
phagocytes, especially neutrophils
• Prostaglandins
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Inflammatory Response: Cytokines Signal Initiation
• Histamines: from mast cells  swelling, edema,
b. v . dilation
• Interleukins: fever, b.v. gaps  WBC's &
proteins  infection
• Bradykinin: pain & swelling
• Membrane attack complex proteins
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Inflammatory Response: Cytokines Signal Initiation
Figure 24-8: Membrane attack complex
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Acquired Immunity: Antigen-Specific Responses
• Activate T lymphocytes: direct attack
• Activate B lymphocytes to become:
• Memory cells: 20 immune response to that
antigen
• Plasma cells: antibodies – attack that antigen
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Antigen Presentation to Immature T Cells
Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or
"helper" CD4+ cells. Cytotoxic cells directly attack other cells carrying certain foreign or
abnormal molecules on their surfaces. Helper T cells, or Th cells, coordinate immune
responses by communicating with other cells. In most cases, T cells only recognize an
antigen if it is carried on the surface of a cell by one of the body’s own MHC, or major
histocompatibility complex, molecules.
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T Cell Dependent B Cell Activation
A TH2 cell (left), B cell (right), and several
interaction molecules
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B Cell Activation
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ANTIBODIES
STRUCTURE
CLASS
ANTIBODIES
POLYCLONAL.
MONOCLONAL.
Derived from different B
Lymphocytes cell lines
Derived from a single B cell
clone
Batch to Batch variation
affecting Ab reactivity & titre
mAb offer Reproducible,
Predictable & Potentially
inexhaustible supply of Ab
with exquisite specificity
NOT Powerful tools for
clinical diagnostic tests
Enable the development of
secure immunoassay systems.
Acquired Immunity: Antigen-Specific Responses
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Figure 24-13: Functions of antibodies
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The Human Leukocyte Antigen (HLA) System
• Essential to immune function: HLA
molecules present peptide antigens to the
immune system (T-cells)
• Important for self versus non-self
distinction
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HLA Class I Monitors Inside of the Cell
Tapasin
CR
CN
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Dr. Brian Freed
HLA Class II Monitors Outside of Cell
Peptides
Extracellular
Proteins
DM
monitors
peptide
specificity
for DR
DM
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Dr. Brian Freed
HLA Class I and II Molecules Have a Distinct Structure and Function
•Binds 8-10mers
•Expressed on most
Nucleated cells
•Presents Cytosolic
Proteins to CD8+ T cells
•Binds 13-25mers
•Expressed on APCs,
Macs, B cells, activated
T cells
•Presents Vesicular
Proteins to CD4+ T cells
 
 
2 3
 
Class I
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Class II
BDC
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Humoral
Versus
Cellular
Immune
Response
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Class I (1.1 Mb)
Class III (0.7 Mb)
Class II (2.2
Mb)
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Complement
& cytokines
Transplantion
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Gene
low high resolution typing
“subtype”=01
Allele:
Haplotype:
Genotype:
HLA-DRB1*0401
HLA-DRB1*0401
HLA-DQB1*0302
HLA-DRB1*0301
HLA-DQB1*0201
DRB1*02
HLA-DRB1*04
HLA-DQB1*0302
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J. Noble
Antigen–presenting cells (APCs):
monocytes, macrophages, dendritic cells, B cells
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slides:
www.barbaradaviscenter.com
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T Lymphocytes: Cell Mediated Immunity
• T cell receptors: cell activated to antigen
• Major histocompatability complex (MHC)
• Helper T cells:
• Cytotoxic T cells: perforins, granzymes,
(apoptosis) & Fas
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Defenses against Bacteria: Complement P Activates:
• Make membrane attack complex  kill
bacteria
• Inflammation: + recruit phagocytes, B & T
lymphocytes
• (Acquired response  antibodies, cytotoxic
Ts … if needed)
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T Lymphocytes: Cell Mediated Immunity
Figure 24-16: T lymphocytes and NK cells
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Antigen Presentation
Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or
"helper" CD4+ cells. Cytotoxic cells directly attack other cells carrying certain foreign or
abnormal molecules on their surfaces. Helper T cells, or Th cells, coordinate immune
responses by communicating with other cells. In most cases, T cells only recognize an
antigen if it is carried on the surface of a cell by one of the body’s own MHC, or major
histocompatibility complex, molecules.
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Defenses against Bacteria: Complement P Activates
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Figure 24-17: Immune responses to bacteria
Viral Defense:
Summary of Innate & Acquired Responses
• Circulating antibodies inactivate or target virus
(opsins)
• Macrophage  inflammation, interferon, cell
activation
• Helper, cytotoxic T, NK & B cells 
plasma c. antibodies
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Viral Defense:
Summary of Innate & Acquired Responses
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Figure 24-18: Immune responses to viruses
Allergic Response:
Inflammation Reaction to Non-pathogen
• First exposure: sensitization
• Activation
• Clone B cells
• Form antibodies
• Memory cells
• Re-exposure
Many antibodies
Activated Ts
• Intensified
• Inflammation
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Allergic Response:
Inflammation Reaction to Non-pathogen
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Figure 24-19: Allergic responses
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Blood Types:
Like Antibodies & antigens will agglutinate
• Antigens on RBCs (A, B, AB or none = O)
• Antibodies in plasma (anti A, anti B, anti AB)
• Rh antigens & antibodies
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• Although there are over 600 known red blood cell
antigens organized into 22 blood group systems,
routine blood typing is usually concerned with
only two systems: the ABO and Rh blood group
systems. Antibody screening helps to identify
antibodies against several other groups of red
blood cell antigens.
• Some of the other groups are the Duffy, Kell,
Kidd, MNS, and P systems
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Blood Types:
Like Antibodies & antigens will agglutinate
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Figure 24-20a: ABO blood groups
Autoimmune Diseases: Failure of “Self-Tolerance”
• Type I diabetes mellitus – immune system attacks
- cells
• Graves disease – antibodies mimic TSH
hyperthyroidism
• Multiple Sclerosis – autoimmine attack on
myelin nerve sheath
• Rheumatoid arthritis – autoimmune attack on
joint cartilage
• Myasthenia gravis – ACh-receptors at endplate
attacked by immune system
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Interaction of Nervous, Endocrine & Immune
Systems
• Much yet to understand
• Neuroimmunomodulation
• All three share some:
• Signal molecules
• Receptors
• Overlapping responses
• Fight or flight
• Chronic stress
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Interaction of Nervous, Endocrine & Immune
Systems
Figure 24-21: Model for interaction between nervous, endocrine, and immune systems
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Summary
• Body defends itself with barriers, chemicals &
immune responses
• WBCs and relatives conduct direct cellular attack:
phagocytosis, activated NK & cytotoxic T cells and
produce attack proteins (i.e. antibodies,
complement, & membrane attack complex)
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Summary
• Cytokines, communicate cell activation,
recruitment, swelling, pain, & fever in the
inflammation response
• Defense against bacteria is mostly innate while
viral defense relies more on acquired immune
responses
• Autoimmune diseases are a failure of selftolerance
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