Immunotherapy is a medical treatment that makes use of the body’s own immune system to fight disease, particularly cancer . An immune response generally depends on immune system molecules called antibodies. Antibodies bind to molecules called antigens on the surface of pathogens (disease-causing agents), marking a pathogen for attack by immune cells. Infectious pathogens may be readily recognized as foreign by the immune system. Cancer cells, however, begin as body cells, which may make it difficult for the immune system to recognize and attack them. Immunotherapies boost immune activity or assist the immune system in targeting cancer cells. They may have fewer or less severe side effects than treatment with radiation or chemotherapy .
There are many different kinds of immunotherapy. They include (1) monoclonal antibody therapy, (2) chimeric antigen receptor (CAR) T-cell therapy, (3) checkpoint inhibitors, and (4) cancer vaccines, among others. Different types of immunotherapy are effective against different cancers.
Monoclonal antibodies are molecules designed to target a specific antigen. They are engineered in a laboratory and then copied in large numbers. In monoclonal antibody therapy, antibodies designed to target cancer cells are injected into the body. The antibodies bind to antigens on the cancer cells, marking them for attack by the immune system.
Some immune cells, called T cells, can bind directly to pathogens using molecules on their surface, called receptors. In CAR T-cell therapy, doctors remove T cells from the body. They then alter the T cells in a lab to add a receptor that binds to cancer cell antigens. The T cells are injected back into the body, where they target and destroy cancer cells.
Many immune cells have mechanisms to prevent an immune response, sometimes referred to as “checkpoints.” In a healthy body, checkpoints help to prevent an immune response from being triggered by body cells. Some cancers, however, can activate or deactivate checkpoints much as healthy cells do, evading attack by the immune system. Drugs called checkpoint inhibitors can be administered to disable checkpoint mechanisms, enabling an immune response.
Cancer vaccines work in much the same way as vaccines against infectious illness. But cancer vaccines aim to destroy a disease already inside the body, rather than to prevent a disease from infecting the body. A cancer vaccine may contain cancer cells, parts of cancer cells, or purified antigens. Introduced into the body, the vaccine triggers the immune system to manufacture antibodies to attack cancer cells.
Several other immunotherapies are also used to treat cancer. In general, they consist of medicines that boost immune system function.
