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Immunotherapy & Cancer
The immune system is the body's natural defense mechanism to prevent and combat disease. The primary disease-fighting functions of the immune system are carried out by white blood cells. In response to the presence of disease, white blood cells can mediate two types of immune responses, referred to as innate, or natural, immunity and adaptive, or acquired, immunity. Together the innate and adaptive arms of the immune system generally provide an effective defense against a broad spectrum of diseases that surround us throughout our lives.
Despite the effectiveness of the immune system in defending the body against infectious disease, it is ineffective in defending the body against a cancer once it has appeared. The immune system has developed numerous immune suppression mechanisms to prevent it from destroying a person's normal tissue. These same mechanisms can prevent an immune response from being mounted against cancer cells. In addition, the cancer cells themselves can make changes that reduce the ability of the immune system to attack the tumor.
Immunotherapy utilizes a person's immune system in an attempt to combat diseases, including cancer. There are two forms of immunotherapy used to treat various diseases: passive and active. Both types of immunotherapy have been used with success to treat a number of different diseases. For example, active immunotherapies in the form of preventative vaccines have enabled the complete or virtual elimination of viral diseases like small pox and polio.
Passive immunotherapy is characterized by the introduction of antibodies specific to a particular antigen into a patient. When antibodies are infused into a cancer patient, they attach to any cell that displays the antigen. The patient's immune system then responds to eliminate those specific cells tagged by the antibody. Alternatively, radioactive molecules or toxins can be attached to an antibody before it is infused into the patient to kill the tagged cells directly. Although the protection that is provided by a passive immunotherapy is immediate, it is temporary. Consequently, while passive immunotherapies have shown clinical benefits in some cancers, and some have improved safety profiles compared to existing therapies, they require repeated infusions and can cause the destruction of normal cells as well as cancer cells.
An active immunotherapy generates an adaptive immune response by introducing an antigen into a patient, often in combination with other components that can enhance an immune response to the antigen. The specific adaptive immunity generated can include both the production of antigen-specific antibodies made by B-cells, known as humoral immunity, and the production of antigen-specific T-cells, known as cellular immunity. Active immunotherapies have been successful in preventing many infectious diseases, such as measles, mumps or diphtheria and are being actively explored for their ability to combat cancer.