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The Immune System
Dr. Timmel
What is the function of the immune
system?
To fight infection through the production of
cells that inactivate foreign substances or
cells.
 Some defenses are non-specific and some
are specific.
 These defenses work together to both
prevent and fight off disease.

What is disease?
Any change, other than an injury, that
disrupts the normal functions of the body.
 What this really means is that something is
forcing your body out of equilibrium.
 If an organism is in a disease condition for
too long a period of time, death will ensue.

What are pathogens
Pathogens are disease causing agents.
 Diseases caused by pathogens are
generally called infectious diseases.
 Examples of pathogens are:

Viruses (the flu, the common cold, warts)
 Bacteria (strep throat, anthrax)
 Protists (malaria, sleeping sickness)
 Worms (tapeworms)
 Fungi (Athlete’s foot)

Non-specific defenses
First line of defense: The bodies most
important nonspecific defense is the skin.
 This first line of defense also consists of
mucus, sweat and tears.
 Consists of physical and chemical
defenses.
 Any break in the skin is a possible avenue
into your body for a disease causing
agent.

Second line of defense
The inflammatory response. A
nonspecific response to tissue damage
caused by injury or infection.
 Infected tissue may become swollen and
painful.
 A fever is often a component of the
inflammatory response.

What are antigens?
A foreign substance which triggers a
response by your immune system.
 Viruses, bacteria and other pathogens are
examples of antigens.
 The antigen is what is making you sick.
 Allergies are also caused by antigens that
aren’t really dangerous, but trick your body
into acting as if they were. (eg. Pollen).

What are antibodies
Antibodies are proteins that recognize and
bind to antigens, inactivating them.
 Each antibody is specific to a certain
antigen.
 Once a particular antibody is produced by
a body, memory B-cells become capable
of quickly producing them should the body
encounter the same antigen in the future.

Vaccination
The injection of a weakened or killed form
of a pathogen to produce immunity.
 Vaccines give the patient an active
immunity against a particular disease and
have saved millions of lives.

Lymphocytes

As we should recall from the circulatory system, there
are four different types of white blood cells.

T-Cells: Provide a defense against abnormal cells and pathogens inside living cells.
T-Cells are formed in the Thymus gland. 2 types: Helper and Killer T cells.

B-Cells: Provide immunity against pathogens and antigens in the body fluids. BCells are formed in the Bones. These cells produce the antibodies that either disable
or destroy the pathogen.

Phagocytes: Cells that devour foreign cells through phagocytosis

Macrophages: Very large phagocytes. Assist the activation of B and T Cells.
Autoimmune disease
When the body’s own immune system
attacks it’s own cells.
 The immune system produces “antiself”
antibodies.
 Examples are type one diabetes, MS and
AIDS.

AIDS

Acquired Immune Deficiency Syndrome.
A viral disease in which the body’s T-cells
are destroyed, leaving the body
susceptible to secondary infections.
 Causes by the HIV (Human
immunodeficiency virus). It is a retrovirus,
meaning it contains RNA and not DNA

What is lymph?
It is a clear fluid that is lost by the blood to
the surrounding tissue.
 Travels through the lymphatic system: A
network of vessels, nodes and organs
which collects fluids and returns them to
the circulatory system.
 Contains a large number of white blood
cells.

What are lymph nodes?
Part of the lymphatic system, lymph nodes
are small bean shaped enlargements that
filter the lymph and capture bacteria and
other microorganism that cause disease.
 When the doctor says you have swollen
glands, they are actually referring to your
lymph nodes. They get larger when you
are fighting an infection.

Other organs of the immune
system
In addition to lymphocytes, lymph and
lymph nodes, one gland and one other
organ play important roles.
 Thymus gland. As mentioned earlier, TCells mature in the thymus gland.
 Spleen: helps to cleanse the blood and
remove damaged cells from the circulatory
system. Also contains phagocytes.
