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Getting to Know: Immune
Think of the last time that you caught a cold. Do you remember how it felt? You probably had a cough and a stuffy nose. Perhaps you felt tired, lethargic, and you may have had a fever. You couldn’t wait to feel better. What you may not have realized at the time was that your body was already working hard to get rid of pathogens, the viruses or bacteria that were making you sick. Your nose was stuffy because your body produced extra mucous to trap pathogens. As you sneezed and coughed, you were forcing the mucous and pathogens out. When we feel sick, we are often feeling
the effects of our bodies fighting pathogens.
Your body’s immune system is comprised of all of
your body’s natural defenses against pathogens,
from the outer layer of skin that keeps pathogens out to the white blood cells that attack
foreign bodies inside your bloodstream. In this section, you will investigate what the immune
system does and how it works.
What is the function of the immune system?
The function of the immune system is to be the body’s barrier to disease and pathogens. The first line of defense against infection is the skin. Without the skin, pathogens would have free access to many of the body’s tissues. The skin therefore plays a very important role in keeping pathogens out of the body.
However, sometimes pathogens do get into the body. When this happens, the immune system begins to search for and destroy the invaders. How does the immune system fight an infection?
When pathogens attack the body, they can cause an inflammatory response. Blood circulation
increases around the pathogen. This brings many white blood cells called phagocytes to
counter the effects of the pathogen. These cells envelop and absorb the pathogens. They then
dissolve the pathogens with chemicals.
Misconception 1: When I get sick, I sometimes get a fever. Is that a negative side
effect of the infection?
The fever you feel when you are sick is actually a part of your body’s response to the
infection. By raising your internal temperature, your body is creating an inhospitable
environment for infectious agents.
Concept: Immune
Getting to Know
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What does the lymphatic system do?
The lymphatic system consists of a network of vein-like
structures and glands that produce a substance called
lymph. Lymph contains billions of white blood cells.
Clusters of cells called lymph nodes are found at certain
points in the lymphatic system. The nodes collect dead
pathogens and remove them from the lymph.
The lymph nodes also contain special blood cells called
lymphocytes. These cells manufacture antibodies, which
are specialized molecules that can be customized so
that they will only attack a particular type of pathogen.
All pathogens contain special markers on them called
antigens. These antigens are unique to that pathogen.
Antibodies can be tailored so they fit onto the pathogen’s
antigens just like the pieces of a jigsaw puzzle.
The first time that a particular pathogen attacks the
body, it takes some time for the lymphocytes to produce
antibodies that correspond to that pathogen. However,
if the same pathogen ever attacks the body again, the
lymphocytes can produce the same antibodies again
very quickly. This is known as gaining “immunity” to that
pathogen.
The lymphatic system
produces and circulates
lymph in the body.
What do immunizations do?
Immunity can be gained in other ways as well. Immunizations, or vaccines, are special
injections that contain dead or weakened pathogens. The pathogens are harmless, but
when a person receives the injection, their body still learns to recognize them. That way,
the body learns how to fight that disease without the person ever becoming sick from it.
Immunizations have helped to greatly reduce and even eliminate some historically significant
diseases such as polio and smallpox.
Misconception 2: Are vaccines the same as the body’s immune cells?
Vaccines are injections that create the artificial “memory” of a pathogen so that our
bodies can recognize and attack that pathogen in the future. Vaccines usually contain
weakened or dead pathogens and are different from the antibodies produced by the
immune system.
Concept: Immune
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.