Download The Immune System

The Immune
System
Immune system
 Recognizes, attacks, destroys, and
“remembers” each type of pathogen that enters
the body
 Immunity is the process of producing cells that
inactivate foreign substances in the body
 2 categories in the immune system
 Specific defenses
 Nonspecific defenses
Nonspecific defenses
 Include physical and chemical barriers (skin, mucus,
sweat, tears)
 Keep pathogens out of the body
 Body secretions (mucus, saliva, and tears) contain
lysozyme, an enzyme that breaks down bacteria
 Oil and sweat glands provide an acidic environment
that inhibits bacterial growth
 Mucus in nose and throat trap pathogens
 Cilia in nose and throat push pathogens away from
lungs
 Digestive enzymes break down pathogens
Second line of defense
 Inflammatory response-body responds to
tissue damage caused by injury or
infection
 Millions of white blood cells fight infection
 Blood vessels near would expand and
allow WBCs to pass into wounded area
 WBCs engulf bacteria; affected area can
become swollen and painful
Macrophage
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Histamine Production
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Fever
 Immune system releases chemicals that
raise the body’s core temperature
 Higher temperature helps to destroy
pathogens (cannot survive high heat)
 Fever also increases heart rate which
allows WBCs to get to would or infection
faster
Interferon
 Proteins produced by viral-infected cells
that help other cells resist viral infection
 Interferons inhibit the synthesis of viral
proteins in infected cells and block viral
reproduction
 Gives immune system time to respond
Specific defenses
 Attack particular disease-causing agents
 Make up the immune response
 Antigens (viruses, bacteria, other
pathogens) trigger this response
 Two types of lymphocytes in the immune
response
 B lymphocytes (B cells)
 T lymphocytes (T cells)
B cells
 Provide immunity against antigens in body
fluids
 Recognize antigens, grow and divide rapidly to
make plasma cells and memory B cells
 Plasma cells release antibodies (proteins that
recognize and bind to antigens) into the blood
to go and attack the pathogen
 Memory B cells remain capable of producing
the antibodies in case a second infection
occurs
Antibody
Immunity
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T cells
 Provide defense against abnormal cells and
pathogens living in cells (cancerous cells or
viral-infected cells)
 Cell-mediated immunity
 Also helps against infections by fungi or
protists
 T cells become killer T cells, helper T cells,
suppressor T cells, and memory T cells
Cellular
Immunity
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Killer T cells
 Track down and destroy bacteria, fungi,
protozoa, or foreign tissue that contains a
pathogen or antigen
Helper T cells and
memory T cells
 Helper T cells produce memory T cells
 Memory T cells cause a secondary
response in case of another infection by
the same pathogen
Suppressor T cells
 Release substances that shut down the
killer T cells
Active immunity
 Caused by injection of a weakened or mild
form of a pathogen to produce immunity
(vaccines)
 Modern vaccines stimulate the immune system
to create millions of plasma cells ready to
produce specific types of antibodies
 Can also be developed after natural exposure
Passive immunity
 Antibodies produced by other animals are
injected into the body to produce antibodies
 Last only a short time before the body destroys
them
 Can be developed from natural exposure or
vaccines
 Antibodies can also move across the placenta
during pregnancy or be passed to infants in
breast milk