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Immune System
AND INFECTIOUS DISEASES
Immune System
● The network of cells, tissues,
and organs that work together
to protect the body against
infectious invaders.
● The organs involved in the
immune system are called the
lymphatic system and consist of:
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Thymus
Spleen
Bone Marrow
Lymph Nodes
● These are important parts of the
immune system because they
produce or store leukocytes
Lymphatic System
● Macrophages are a type of phagocyte that migrate
through the body by using the lymphatic system.
Leukocytes
Leukocytes circulate through the blood and lymphatic system
and there are two types:
Phagocytes
● Cells that engulf and break
down the invading organism
● Most common is neutrophils,
which fight bacteria
Lymphocytes
● cells that allow the body
to remember and
recognize previous
invaders and help the
body destroy them
● B-cells and T-cells find
organisms identified by
antibodies and destroys
them
Lymphocyte Response
● When foreign organisms (antigens) are recognized by the body
B-cells produce antibodies
● Antibodies are proteins that are developed to lock onto specific
antigens
● These antibodies will be present in your body for life, so the next
time that antigen enters your body it is destroyed very quickly
● That is how immunizations work, they introduce a weakened
antigen into your body, so your body
can produce antibodies in case a
stronger antigen returns
● Antibodies cannot destroy these
antigens on their own, the T-cells
destroy the antigens
Types of Immunity
● Humans have three different types of immunity:
○ Innate – immunity you are born with
○ Adaptive – immunity that develops throughout our lives
○ Passive – immunity that is borrowed from another person or
source
Innate Immunity
● This includes lots of our external
barriers that prevent antigens from
ever entering our bodies
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Our skin prevent germs from entering our blood stream
Secretions give the skin a pH between 3 and 5, acidic enough to
prevent colonization of many microbes and secretes lysozyme,
which digests bacterial cell walls
If there is a break in the skin, it will try to heal and blood flows
outward preventing the infection from getting inside
Our breathing passages are covered in hairs and mucus that are
meant to trap foreign organisms and expel them from our bodies
Organisms that enter through our mouth will either be killed by
the chemicals in our saliva or the acid in our stomach
Adaptive Immunity
● Adaptive immunity includes the
antibodies we develop by being
exposed to different diseases
throughout our lives and the
vaccinations we receive
Types of Immunity
Passive Immunity
● Sometimes we can borrow immunity from another
source, but this does not usually last for very long
● The most common example of this is when babies get
antibodies from the mother’s breast milk, which is
one reason breast feeding is beneficial for babies
Inflammatory Response
● Inflammatory response is when fluid and white blood cells
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leak out of the blood vessels and into the tissues.
The white blood cells fight the pathogens
During an inflammatory response, the blood vessel get
wider to increase the flow of blood to that area
Because of the increase blood flow and the fluid leaking
into the tissue, an inflamed area will look red and swollen.
Also, the inflamed area will feel warn to the touch.
In some cases, the inflammatory response will result in you
having a temperature. This high temperature keeps
pathogens from reproducing.
Inflammatory Response
● Triggered by the release of histamines (which are
sometimes released when harmless substances enter
the body causing an allergic reaction)
Infectious Diseases
● a disease that can be passed from one organism to
another (called antigens or pathogens)
● When you have an infectious disease, a pathogen has
gotten into your body and harmed it
● Pathogens make you sick by damaging individual
cells
● There are four major groups of pathogens
Bacteria
● Bacteria are single cell organisms
● Bacteria are classified as PROKARYOTES
● Most bacteria cannot make their own food; they
have to break down, or decompose, other living
things to obtain their energy
● Most bacteria do not cause diseases
● Bacteria are almost everywhere:
air, food, water, soil.
● Example: Strep throat
Viruses
● Virus – a nonliving particle consisting of a core of
hereditary material surrounded by a protein coat.
● Viruses can reproduce ONLY inside a living
cell.
● Examples: Flu, common cold
Fungi
● Most fungi are multicellular
● Fungi obtain food by secreting enzymes onto the
dead material outside of their bodies (external
digestion). The fungi then absorb the nutrients
into their cells. Organisms that feed this way are
called SAPROPHYTES
● Example: Athlete’s foot
Protists
● One cell organisms (unicellular) that have
organelles
● Example: Malaria
Man-Made Defenses
● PASTERUIZATION – a heating process that is used
today to kill microorganisms in food products such
as milk
● ANTIBIOTICS – a chemical that is used to kill
bacteria or slow their growth without harming your
body cells. Unfortunately, there is no way to cure
viral diseases.
● VACCINE – introducing the body to a weaker or
dead form of a pathogen, so we can generate
antibodies against that disease
Famous Fights Against Disease
● Louis Pasteur
○ Proved that microbes caused infectious disease.
○ He showed these microbes were in the air.
○ Food could avoid contamination by being heated in a flask that
did no allow bacteria from the air to get in.
○ His methods led to development of pasteurization.
Famous Fights Against Disease
● Jonas Salk
○ Invented the polio vaccine.
○ In the 1950’s there was an outbreak of polio
that killed over 3,ooo and left over 21,000
paralyzed.
○ It was the first mass distributed vaccine that
was safe for public use.
○ It used a dead form of the virus, so people
would generate antibodies to it without ever
getting sick
Spread of Disease
● PERSON-TO-PERSON TRANSFER
○ Diseases can be transferred by direct contact such as kissing and shaking
hands
○ Diseases can be transferred by indirect contact such as sneezing and
coughing
● CONTAMINATED OBJECTS
○ Food and water can become contaminated
○ You can get ill by using contaminated objects such as towels and silverware
● ANIMAL BITES
○ An infected animal can pass on pathogens through their bite
○ Examples: rabies (dog, raccoon), Lyme disease (tick), malaria (mosquitoes
in tropical areas)
● PATHOGENS FROM THE ENVIRONMENT
○ Some pathogens live naturally in the soil and water
○ Example: tetanus, botulism (causes food poisoning)
Super-Bugs
● Antibiotics kill bacteria, but if antibiotics are not taken their full
term too many bacteria are left alive, so your immune system
can’t kill the rest before they begin reproducing.
● The bacteria left are ones resistant to the antibiotic, which
reproduce asexually creating identical copies (also resistant to
antibiotics).
● So, next time
you take the
antibiotic to
kill the
bacteria they
are
immune and
won’t die.
Spread of Infection
● The spread of infectious can be affected by several
factors:
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Amount of time the person is contagious
How the disease spreads (STD, airborn, through bodily fluids,
contact, etc)
Population density
Population Mixing
● http://www.learner.org/courses/envsci/interactives
/disease/disease.html
Non-Infectious Disease
● A disease that is not
contagious (cannot be
passed from person to
person or animal to person)
● These are not caused by
pathogens (germs)
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Examples:
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Heart disease
Cancer
Arthritis
Autoimmune Diseases
● An autoimmune disease occurs when the immune
system attacks and destroys healthy body tissue.
● The causes of these disorders are unknown for the
most part.
● We suspect some are caused by bacteria, some by
drugs, and some people may just have a genetic
predisposition.
● Examples of autoimmune diseases are:
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Lupus
Diabetes Type I
Guillain-Barre Syndrome
HIV / AIDS
● HIV (human immunodeficiency virus) – the virus
that attacks the immune system causing patients to
become more and more vulnerable to infection
● AIDS (acquired immune deficiency syndrome) – this
is the disorder that occurs after symptoms of the
virus begin to present themselves.
● This is an infectious disease because it is transmitted
from person to person through bodily fluids.
● Tomorrow we will complete the AIDS Lab. You will
learn more about this disease when you read the prelab information.