Immunotherapies were tested using clinical trials in the 1970's; some became
widely used beginning in the1980s. There are many types of immunotherapies,
and all of them work with the immune system.
What is the immune system?
The immune system is a body-wide network of biological processes designed to
safeguard health (learn much more about this in: "What We Know About Cancer -
Research Hallmarks: Circa Today"). It is the body's own power of protection. Cells,
tissues, and organs help create immune system function.
Immune cells circulate throughout the body and are responsible for recognizing
foreign substances and eliminating them. The immune system consists of many
different types of white blood cells, including B lymphocytes (or B cells), T
lymphocytes (or T cells), and others such as natural killer cells, dendritic cells, monocytes, eosinophils, and basophils.
Cells destined to become immune cells, as all blood cells, arise in the body's bone
marrow from stem cells. Some develop into myeloid progenitor cells while others
become lymphoid progenitor cells.
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The myeloid
progenitors develop
into red blood cells and other cells that
respond early and
nonspecifically to
infection.
Lymphoid precursors develop into small white
blood cells called
lymphocytes.
Lymphocytes respond
later in the course of
infection.
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| Image courtesy of the National Cancer Institute |
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They mount a more
specifically tailored
attack after antigenpresenting
cells such as
dendritic cells identify and present
their "catch" in the form
of antigen fragments.
T cells contribute to the body's immune defenses in two major ways. Some help
regulate the complex workings of the overall immune response, while others are
cytotoxic and directly contact infected cells and destroy them.
The key to a healthy immune system is its ability to distinguish between the body's
own cells, recognized as "self," and foreign cells, or "nonself." The body's immune
defenses normally coexist peacefully with cells that carry distinctive "self" marker
molecules. Immune defenders launch an attack when they encounter foreign cells
or organisms carrying markers of "nonself".
What is an antigen?
An antigen is a substance (often a protein) that causes the immune system to
make a specific response. Any nonself substance capable of triggering an immune
response is known as an antigen. An antigen can be a whole nonself cell, a
bacterium, a virus, an MHC marker protein or even a portion of a protein from a
foreign organism.
Antigens can be manufactured in a laboratory or produced naturally by the body.
Some forms of immunotherapy contain antigens.
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At the molecular level, an antigen is
characterized by its ability to be "bound" at the antigen-binding site of an
antibody.
Also, each antibody binds to a specific
antigen; an interaction similar to a lock
and key.
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| Image courtesy of the National Human Genome Research Institute |
