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Immune System
First line of defense
• The skin serves as a physical barrier to prevent the
passage of many disease-causing microorganisms. The
skin is also slightly acidic and has good bacteria.
Antigens
• Antigens are
substances that cause
the immune system to
attack. An example of
an antigen is a surface
protein of a flu virus.
Cells produce
antibodies to fight
antigens. Antibodies
destroy pathogens
directly or signal
immune cells that
pathogens are present.,
Specific mechanisms of host
resistance
• This specific immune response enables the
body to target particular pathogens and
pathogen-infected cells for destruction. It
depends on specialized white blood cells called
lymphocytes produced in the bone marrow .
• T-cells (produced from lymphocytes that
matured in the thymus gland)
• B-cells (produced from lymphocytes that
matured in the bone marrow).
Production and
Maturation
• All lymphocytes,
macrophages and red
blood cells produced
in bone marrow and T
cells mature in
Thymus and B cells
stay in bone marrow
to mature
T-helper
• These cells travel through the blood and lymph,
looking for antigens –markers on foreign cells.
Upon locating an antigen, they notify other cells
to assist in combating the invader.
• T-helper cells do this through the use of
cytokines (or specifically, lymphokines) which
help destroy target cells – T-killer cells, activate
B cells and stimulate the production of healthy
new tissue. Interferon is an example of such a
cytokine – one treatment of HIV which infects
and kills T-helper cells.
• T-killer
cells
get help
from Thelper
cells to
turn on
then do
the
killing
B-cells get
turned on by
T-helper
cells to
make
specific
antibodies
that tell
macrophage
to get them
out of the
way
Vaccines
• Vaccinations give the body a preview of
dangerous antigens.
• This allows the body to develop antibodies
to fight this antigen.
• The body is able to generate an immune
response quickly to prevent the disease
from doing harm to the body.
Brain Pop Video
Common pathogens
• Pathogens cause disease.
• Bacteria and viral pathogens are the most
common causes of human disease.
Bacteria
• Bacteria can also cause infections.
• When bacteria enters a host they are
able to reproduce in large numbers and
may produce toxins that affect the
health of the host.
• The bacteria and their toxins are
perceived as antigens by the body.
• Antibiotics can be an effective
treatment for bacterial infections.
Viruses
• Viruses lack ribosomes and are not able to
reproduce on their own. Viruses infect
cells and use the cellular components to
reproduce and spread to other cells.
Virus Infection
Viruses
• When necessary viruses are treated with
anti-viral medications that prevent their
reproduction within the host. Antibiotics
are not effective against viruses.
Examples of viruses
• Influenza (flu)
• Herpes
• HIV
HIV
• HIV attacks key cells involved in the
bodies immune system.
• Infected individuals can not recognize
antigens or are not able to mount a
response.
• These individuals can then be killed by
“harmless” diseases.