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Immunotherapy (sometimes called biological therapy) attempts to stimulate the immune system to reject and destroy tumors. The concept of immunotherapy is based on the body's natural defense system, which protects us against a variety of diseases. Although we are less aware of it, the immune system also works to aid our recovery from many illnesses.

For many years, physicians believed that the immune system was effective only in combating infectious diseases caused by such invading agents as bacteria and viruses. More recently, we have learned that the immune system may play a central role in protecting the body against cancer and combating cancer that has already developed.

This latter role is not well understood, but there is evidence that, in many cancer patients, the immune system slows down the growth and spread of tumors. The body's ability to develop an immune reaction to tumors may help determine which patients are cured of cancer using conventional therapies, including surgery, radiation and drugs.


Organs involved in immune function include

  • The spleen
  • Lymph nodes
  • Thymus
  • Bone marrow
  • Tonsils
  • Adenoids
Image courtesy of Mohit Joshi  

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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.


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.

Image courtesy of the National Cancer Institute  


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.


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.

Image courtesy of the National Human Genome Research Institute




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