What Is Immunotherapy (Biological Therapy)?

Biological therapy (also called immunotherapy, biological response modifier therapy, or biotherapy) uses the body's immune system to fight cancer. The cells, antibodies, and organs of the immune system work to protect and defend the body against foreign invaders, such as bacteria or viruses. Doctors and researchers have found that the immune system might also be able to both determine the difference between healthy cells and cancer cells in the body, and to eliminate the cancer cells.

Immunotherapies are designed to boost the immune system, either directly or indirectly, by assisting in:

  • Making cancer cells more recognizable by the immune system, and therefore more susceptible to destruction by the immune system
  • Boosting the killing power of immune system cells
  • Changing the way cancer cells grow, so that they act more like healthy cells
  • Stopping the process that changes a normal cell into a cancerous cell
  • Enhancing the body's ability to repair or replace normal cells damaged or destroyed by other forms of cancer treatment, such as chemotherapy or radiation
  • Preventing cancer cells from spreading to other parts of the body

How does the immune system fight cancer?

The immune system includes different types of white blood cells - each with a different way to fight against foreign or diseased cells, including cancer:

  • Lymphocytes—white blood cells, including B cells, T cells, and NK cells
    • B cells—produce antibodies that attack other cells
    • T cells—directly attack cancer cells themselves and signal other immune system cells to defend the body
    • Natural killer cells (NK cells)—produce chemicals that bind to and kill foreign invaders in the body
  • Monocytes—white blood cells that swallow and digest foreign particles.

B cells, T cells, natural killer cells, and monocytes are white blood cells in the blood and thus, circulate to every part of the body, providing protection from cancer and other diseases. Cells secrete two types of substances: antibodies and cytokines. Antibodies respond to (harmful) substances that they recognize, called antigens. Specific (helpful) antibodies match specific (foreign) antigens by locking together. Cytokines are proteins produced by some immune system cells and can directly attack cancer cells. Cytokines are "messengers" that "communicate" with other cells.

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