Immunotherapy, also called biological therapy, is a type of cancer treatment that uses the body's immune system to fight cancer. The therapy mainly consists of stimulating the immune system with highly purified proteins that help it do its job more effectively. To help understand the role that biological agents play in cancer treatment some understanding of how the normal immune system works is helpful.
How The Immune System Works
The Immune system is a complex network of cells and organs that work together to defend the body against foreign substances (antigens) such as bacteria, a virus or tumor cell. When the body discovers such a substance several kinds of cells go into action in what is called an immune response. Below is a description of some of the cells that are part of the immune system.
Macrophages are the body's first line of defense and have many roles. They are the first cells to recognize and engulf foreign substances (antigens). They break down these substances and present the smaller proteins to the T lymphocytes. (T cells are programmed to recognize, respond to and remember antigens). Macrophages also produce substances called cytokines that help to regulate the activity of lymphocytes.
Lymphocytes are one of the main types of immune cells. They are divided mainly into B and T cells.
B lymphocytes produce antibodies - proteins (gamma globulins) that recognize foreign substances (antigen) and attach themselves to them. Each B cell is programmed to make one specific antibody. When a B cell comes across its triggering antigen it gives rise to many large cells known as plasma cells. Each plasma cell is essentially a factory for producing antibody. An antibody matches an antigen much like a key matches a lock. Whenever the antibody and antigen interlock, the antibody marks the antigen for destruction. B cells are powerless to penetrate the cell so the job of attacking these target cells is left to T lymphocytes. lymphocytes are cells that are programmed to recognize, respond to and remember antigens. T cells contribute to the immune defenses in two major ways. Some direct and regulate the immune responses. When stimulated by the antigenic material presented by the macrophages, the T cells make lymphokines that signal other cells. Other T cells are able to destroy targeted cells on direct contact.
Dendritic cells are known as the most efficient antigen-presenting cell type with the ability to interact with T cells and initiate an immune response. Dendritic cells are receiving increasing scientific and clinical interest due to their key role in the immune response and potential use with tumor vaccines.
White Blood Cells
There are different types of white blood cells that are part of the immune response. Neutrophils or granulocytes are the most common immune cells in the body. With an infection, their number increases rapidly. They are the major components of pus and are found around most common inflammations. Their job is to eat and destroy foreign material.
Basophils and eosinophils are white blood cells that contain large granules inside the cell. They interact with certain foreign materials. Their increased activity may lead to an allergic reaction.
The immune response is a coordinated effort. All of the immune cells work together, so they need to communicate with each other. They do this by secreting a large number of special protein molecules called cytokines that act on other cells. There are many different cytokines. Examples of these are interleukins, interferons, tumor necrosis factors, prostaglandins and colony-stimulating factors. Some immunotherapy treatment strategies involve giving larger amounts of these proteins by an injection or infusion. This is done in the hope of stimulating the cells of the immune system to act more effectively or to make the tumor cells more recognizable to the immune system.
Caution: There are people who promote unproven therapies as immune system boosters. Be careful when evaluating these claims. The following are types of immunotherapies that are commonly and legitimately used in traditional and scientific medical practice.
Types of Immunotherapy
Biological Response Modifiers
Biological response modifiers are substances that have no direct antitumor effect but are able to trigger the immune system to indirectly affect tumors. These include cytokines such as interferons and interleukins. As mentioned above, this cancer treatment strategy involves giving larger amounts of these substances by injection or infusion in the hope of stimulating the cells of the immune system to act more effectively.
In our body's bone marrow (the soft, sponge-like material found inside bones) blood cells are produced. There are three major types of blood cells; white blood cells, which fight infection; red blood cells, which carry oxygen to and remove waste products from organs and tissues; and platelets, which enable the blood to clot. Cancer treatments such as chemotherapy and radiation therapy can effect these cells which put a person at risk for developing infections, anemia and bleeding problems. Colony-stimulating factors are substances that stimulate the production of blood cells. They do not directly affect tumors but through their role in stimulating blood cells they can be helpful as support of the person's immune system during cancer treatment.
Researchers are developing vaccines that may encourage the patient's immune system to recognize cancer cells. These would in theory work in a similar way as vaccines for measles, mumps and small pox. The difference in cancer treatment is that vaccines are used after someone has cancer. The vaccines would be given to prevent the cancer from returning or to get the body to reject tumor lumps. This is much more difficult than preventing a viral infection. The use of tumor vaccines continues to be studied in cancer treatment clinical trials.
Monoclonal antibodies are laboratory-produced substances that can locate and bind to cancer cells wherever they are in the body. They do this by reacting against tumor-associated proteins on the surface of the cancer cell. These antibodies can be used to see where the tumor is in the body (detection), or as therapy to deliver drugs, toxins, or radioactive material directly to a tumor.
Side Effects of Immunotherapies
Like other forms of cancer treatment, immunotherapies can cause a number of side effects. These side effects can vary widely from patient to patient. Biologic response modifiers, may cause flu-like symptoms including fever, chills, nausea, and appetite loss. Rashes or swelling may develop at the site where they are injected. Blood pressure may also be affected, usually decreasing it. Fatigue is another common side effect of biologic response modifiers. Side effects of colony stimulating factors may include bone pain, fatigue, fever, and appetite loss. The side effects of monoclonal antibodies vary, and serious allergic reactions may occur. Vaccines can cause muscle aches and low-grade fever.