Memmler’s
The Human Body in Health and Disease
11th edition
Chapter 17
Body Defenses, Immunity, and Vaccines
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The Immune System
• Types of general body defenses against disease
• Nonspecific defenses
– Effective against any harmful agent
– present from birth; do not distinguish one type of
threat from another
• Specific defenses
– Effective against a certain agent only
–
Depend on specific lymphocyte activities
–
Produce state of protection (immunity or specific
resistance)
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Why Do Infections Occur?
• Factors involved in infection
– Portal of entry
– Virulence of organism
• Aggressiveness
• Toxin production
– Dose (number) of pathogens
– Individual condition (predisposition) to infection
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Nonspecific Defenses
•
Physical barriers
•
Phagocytes
•
NK Cells (immunological surveillance)
•
Inflammatory response
•
Fever
•
Interferons
•
Complement
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Chemical and Mechanical Barriers
• Skin
• Mucous membranes
–
Cilia
• Body secretions
–
Tears
–
Perspiration
–
Saliva
–
Digestive juices
• Reflexes
–
Sneezing
–
Coughing
–
Vomiting
–
Diarrhea
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Phagocytes
• Engulf and destroy foreign compounds and pathogens
• “First line of cellular defense” against pathogenic invasion
• Types
1. Neutrophils (in bloodstream and tissues)
•
Phagocytize cellular debris or bacteria
2. Eosinophils (less abundant)
•
Phagocytize foreign compounds and antibody-coated
pathogens
3. Macrophages (derived from monocytes)
•
Fixed (permanent residents of certain organs)
•
Free (travel throughout body)
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Natural Killer Cells
Type of lymphocyte
• Can recognize body cells with abnormal membranes
• Found in lymph nodes, spleen, bone marrow, blood
• Secrete protein that breaks down cell membrane
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Immunological Surveillance
•
Constant monitoring of normal tissues by NK cells
–
Normal cells are generally ignored by immune
system
–
Cancer cells often contain tumor-specific
antigens
•
–
NK cells recognize as abnormal and destroy
NK cells recognize bacteria, foreign cells, virusinfected cells, and cancer cells
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NK cells recognize and kill target cells
Step 1: If a cell has
unusual components in its
plasma membrane, an NK
cell recognizes that other
cell as abnormal. Such
recognition activates the
NK cell, which then
adheres to its target cell.
Step 2: The Golgi apparatus
moves around the nucleus until
the maturing face points directly
toward the abnormal cell. A flood
of secretory vesicles is then
produced at the Golgi apparatus.
These vesicles, which contain
proteins called perforins, travel
through the cytoplasm toward the
cell surface.
Step 3: The perforins
are released at the cell
surface by exocytosis
and diffuse across the
narrow gap separating
the NK cell from its
target.
Step 4: As a result of the
pores made of perforin
molecules, the target cell
can no longer maintain
its internal environment,
and it quickly
disintegrates.
Golgi apparatus
NK cell Abnormal
cell
Perforin
molecules
NK cell
Pores produced by the
interaction of perforin
molecules
Abnormal
cell
Immunological Surveillance, cont’d
•
NK cells also destroy abnormal cells
–
Abnormal daughter cells occur during cell
division
–
Some abnormal cells become cancer cells
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NK cells detect and destroy abnormal cells
resulting from faulty cell division
Abnormal cell
Stem cell
Daughter cells
Daughter cells
NK cell identifies and
destroys abnormal cell
Inflammation
Infection is inflammation caused by pathogens
• Inflammatory reaction (response)
– Heat, redness, swelling, pain
– Cells release histamine
– Leukocytes enter tissue
• Granulocytes, macrophages, mast cells
– Leukocytes and plasma produce inflammatory exudate
– Pus is produced
– Lymph nodes enlarge
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The Events in Inflammation
•
Tissue damage causes chemical change in
interstitial fluid
•
Mast cell activation
–
Release of histamine and heparin
• Causes:
•
•
Increased blood flow to area
•
Clot formation
•
Phagocyte attraction (removes debris
and activates specific defenses)
Tissue repair
–
Pathogen removal, clot erosion, scar tissue
formation
Fever
As phagocytes work, they release substances that raise
body temperature
• Pyrogens
– Reset temperature thermostat in hypothalamus
– Stimulates phagocytes
– Increases metabolic rate which may accelerate tissue
defenses and repair process
– Decreases some organisms’ ability to multiply
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Interferons
•
Small proteins released by activated lymphocytes,
macrophages, and virus-infected tissues
•
Trigger antiviral proteins in cytoplasm of nearby
cells
–
•
Do not prevent entry of viruses but interfere
with viral replication
Also stimulate activities of macrophages and NK
cells
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Interferons, cont’d
•
Three types
1. Alpha (α) interferons (produced by virusinfected cells)
•
Attract and stimulate NK cells and give viral
resistance
2. Beta (β) interferons (secreted by fibroblasts)
•
Slow inflammation in damaged area
3. Gamma (γ) interferons (secreted by T cells
and NK cells)
•
Stimulate macrophage activity
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Three Types of Interferons
Alpha (α)-interferons
are produced by cells
infected with viruses.
They attract and
stimulate NK cells and
enhance resistance to
viral infection.
Beta (β)-interferons,
secreted by fibroblasts,
slow inflammation in a
damaged area.
Gamma
()-interferons,
secreted by T cells and
NK cells, stimulate
macrophage activity.
Complement System
•
Complement system (complements antibody
action)
–
•
11 plasma proteins that interact to attach to
foreign cells
Pore formation
–
formed by many complement proteins
–
Destroys integrity of target cell
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Complement System
•
Enhanced phagocytosis
–
Attracts phagocytes and makes target cells
easier to engulf
•
•
= Opsonization
Histamine release
–
By mast cells and basophils
–
Increases inflammation and blood flow to
region
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Summary of the Body’s Nonspecific Defenses
Physical Barriers
Prevent approach of
and deny access to
pathogens
Secretions
Epithelium
Duct of eccrine
sweat gland
Hair
Phagocytes
Remove debris
and pathogens
Neutrophil
Eosinophil
Immunological Surveillance
Destroys
abnormal cells
Natural killer cell
Interferons
Increase resistance of
cells to viral infection;
slow the spread of
disease
Monocyte
Fixed
Free
macrophage macrophage
Lysed
abnormal
cell
Interferons released by activated
lymphocytes, macrophages, or
virus-infected cells
Summary of the Body’s Nonspecific Defenses
Complement System
Attacks and breaks down the
surfaces of cells, bacteria, and
viruses; attracts phagocytes;
Complement
stimulates inflammation
Lysed
pathogen
Inflammatory Response
Multiple effects
Mast cell
• Blood flow increased
• Phagocytes activated
• Damaged area isolated by clotting reaction
• Capillary permeability increased
• Complement activated
• Regional temperature increased
• Specific defenses activated
Fever
Mobilizes defenses;
accelerates repairs;
inhibits pathogens
Body temperature rises above 37.2°C in
response to pyrogens
Immunity
• Power to overcome a specific disease agent
• Innate immunity
– Inherited in genes
• Adaptive immunity
– Develops after birth
– Acquired naturally or artificially
– Active or passive
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Types of
immunity
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Innate Immunity
Differences in physical constitution
• Species immunity
• Individual immunity
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Adaptive Immunity
Develops in a person
• During lifetime
• From encounters with specific harmful agents
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Antigens
• Foreign substances that
• Enter body
• Induce immune response of certain lymphocytes
– T cells
– B cells
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T Cells
• Originate in stem cells in bone marrow
• Change to T cells in thymus
• Become sensitized to specific antigens
• Produce cell-mediated immunity
– Cytoxic T cells
– Helper T cells
– Regulatory T cells
– Memory T cells
• Macrophages
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Activation of a helper T cell by a macrophage (antigenpresenting cell).
Zooming In: What is contained in the lysosome that joins the
phagocytic vesicle?
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B Cells and Antibodies
Antibody (Ab) also known as immunoglobulin (Ig) is
substance produced in response to antigen
• Manufactured by B cells (B lymphocytes)
• Must mature in fetal liver or in lymphoid tissue
• Provides humoral immunity
• Contained in gamma globulin fraction of blood plasma
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Activation of B cells.
The B cell combines
with a specific
antigen. The cell
divides to form
plasma cells, which
produce antibodies.
Some of the cells
develop into memory
cells, which protect
against reinfection.
•Zooming In: What
two types of cells
develop from
activated B cells?
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The Antigen–Antibody Reaction
Complement is the enzymatic activity of a group of
nonspecific proteins in blood that:
• Coats foreign cells
• Destroys cells
• Promotes inflammation
• Attracts phagocytes
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Naturally Adaptive Immunity
Immunity acquired through contact with a specific
disease organism
• Active immunity
• Passive immunity
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Artificially Adaptive Immunity
Vaccination (immunization) can cause a person’s
immune system to manufacture antibodies
• Preventive measure
• Risk of side effects
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Types of Vaccines
• Live
• Attenuated
• Toxoid
• Killed by heat or chemicals
• Antigenic component
• Genetically engineered
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Boosters
• Active immunity does not always last a lifetime
• Repeated inoculations (booster shots) help maintain high
titer of antibodies in the blood
• Number and timing varies with vaccines
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Examples of Vaccines
• Whooping cough (pertussis)
• Diphtheria, tetanus toxoid (Td)
• Haemophilus influenzae type B (Hib)
• Pneumococcal vaccine (PCV)
• Viral
–
Inactivated polio, oral polio
–
Measles (rubeola), mumps, rubella (MMR)
–
Hepatitis B
–
Hepatitis A
–
Chicken pox (varicella); vaccine for shingles now available for those >60 yr
–
Influenza
–
Rabies
–
Rotavirus
–
HPV (human papillomavirus) for girls 11-26
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Passive Immunity
Acquired by administration of immune serum (antiserum)
• Short-lived immunity
• Used in emergencies
• Often derived from animals
• May cause sensitivity reaction
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Disorders of the Immune
System
• Resulting from overactivity
– Allergy
– Autoimmune disease
• Resulting from underactivity
– Hereditary
– Infections
– Environmental
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Allergy
Abnormal reactivity to one’s own tissues
• Factors
– Disease
– Loss of immune system control
– Cross-reaction of antibodies and self antigens
• Treatments
– Immune-suppressing drugs
– Chemotherapy/stem cell replacement
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Immune Deficiency Diseases
Failure of immune system
• May involve any part of system
• Varies in severity
• Congenital or acquired (e.g., AIDS)
• HIV
– A retrovirus; uses reverse transcriptase enzyme
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Multiple Myeloma
Cancer of blood-forming bone marrow cells
• Effects of disease
–
Lowered resistance to infection
–
Anemia
–
Bone pain
–
Bone tissue loss
–
Kidney failure
• Treatment
–
Chemotherapy
–
Bone marrow transplants
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The Immune System and Cancer
• Immune surveillance
– Declines with age
• Immunotherapy
– T cells activated with interleukin
– Vaccines
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Transplantation and Rejection Syndrome
• Caused by normal antigen–antibody reaction
• Reduced by
– Tissue typing
– Immune suppression drugs
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End of Presentation
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