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    Biological Therapies for Cancer: Questions and Answers

    Key Points

    • Biological therapies use the body's immune system to fight cancer or to lessen the side effects that may be caused by some cancer treatments (see Question 1).
    • Biological response modifiers (BRMs) occur naturally in the body and can be produced in the laboratory. BRMs alter the interaction between the body's immune defenses and cancer cells to boost, direct, or restore the body's ability to fight the disease (see Question 3).
    • Biological therapies include interferons, interleukins, colony-stimulating factors, monoclonal antibodies, vaccines, gene therapy, and nonspecific immunomodulating agents (see Questions 4 to 10).
    • Biological therapies can cause a number of side effects, which can vary widely from agent to agent and patient to patient (see Question 11).

    1. What is biological therapy?

    Biological therapy (sometimes called immunotherapy, biotherapy, or biological response modifier therapy) is a relatively new addition to the family of cancer treatments that also includes surgery, chemotherapy, and radiation therapy. Biological therapies use the body's immune system, either directly or indirectly, to fight cancer or to lessen the side effects that may be caused by some cancer treatments.

    2. What is the immune system and what are its components?

    The immune system is a complex network of cells and organs that work together to defend the body against attacks by "foreign" or "non-self" invaders. This network is one of the body's main defenses against infection and disease. The immune system works against diseases, including cancer, in a variety of ways. For example, the immune system may recognize the difference between healthy cells and cancer cells in the body and works to eliminate cancerous cells. However, the immune system does not always recognize cancer cells as "foreign." Also, cancer may develop when the immune system breaks down or does not function adequately. Biological therapies are designed to repair, stimulate, or enhance the immune system's responses.

    Immune system cells include the following:

    • Lymphocytes are a type of white blood cell found in the blood and many other parts of the body. Types of lymphocytes include B cells, T cells, and Natural Killer cells.

      B cells (B lymphocytes) mature into plasma cells that secrete proteins called antibodies (immunoglobulins). Antibodies recognize and attach to foreign substances known as antigens, fitting together much the way a key fits a lock. Each type of B cell makes one specific antibody, which recognizes one specific antigen.

      T cells (T lymphocytes) work primarily by producing proteins called cytokines. Cytokines allow immune system cells to communicate with each other and include lymphokines, interferons, interleukins, and colony-stimulating factors. Some T cells, called cytotoxic T cells, release pore-forming proteins that directly attack infected, foreign, or cancerous cells. Other T cells, called helper T cells, regulate the immune response by releasing cytokines to signal other immune system defenders.

      Natural Killer cells (NK cells) produce powerful cytokines and pore-forming proteins that bind to and kill many foreign invaders, infected cells, and tumor cells. Unlike cytotoxic T cells, they are poised to attack quickly, upon their first encounter with their targets.

    • Phagocytes are white blood cells that can swallow and digest microscopic organisms and particles in a process known as phagocytosis. There are several types of phagocytes, including monocytes, which circulate in the blood, and macrophages, which are located in tissues throughout the body.

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