  |
|
|
|
A vaccine contains an antigen that is designed to stimulate the immune system to respond to a pathogen or other foreign substance that has that antigen. Vaccines are usually considered a preventative measure, such as a vaccine against flu or measles. This approach is not feasible in the case of cancer, however, due to the large number of cancer types, and the unpredictibility of whom might get cancer. Instead, cancer vaccines are therapeutic, used to treat a person who already has cancer.
Although cancer cells can appear very abnormal under the microscope, the immune system may pass them off as normal body cells. In order to mount an immune response against cancer cells, the immune system must detect antigens on the cell surface. Since cancer cells are derived from normal cells, either in many cases they do not produce antigens, or the antigens only stimulate a weak response. Researchers have developed the means to detect cancer antigens that are not so readily apparent. The cytotoxic T cell (CD8 cell) has a central role in the immune response against cancer, since its job is to destroy cells that are infected or abnormal in some way. The immune system has a built-in safety mechanism to prevent an autoimmune attack (against the body's own cells). The CD8 cell must be stimulated by two signals before it can react to the abnormal cell. The first signal is the binding of the T cell receptor with the antigen presented by the Class I major histocompatability complex (MHC). The second signal is the binding of the CD28 protein receptor on the CD8 cell with a protein molecule such as B7. Both the antigen-MHC complex and B7 costimulatory molecules are commonly produced by antigen presenting cells, such as macrophages. Cancer cells are poor antigen presenting cells and may not be able to bind antigen to the MHC molecule, nor secrete B7. Non-specific immunotherapy This type of therapy seeks a broad stimulatory effect on the immune system that respond to cancer cells in a similar manner. Dr. William Coley pioneered in this method by the use of various bacterial agents. These methods were not very successful. The procedure continues to this day in the use of carbohydrate antigens present on the surface of certain encapsulated organisms. Another approach involves gene therapy, which I will discuss in a future article. The method involves introducing genes that code for the formation of cytokines into the cancer cell's DNA. The cell then proceeds to make and secrete the cytokines, which in turn stimulate the immune system.
The copyright of the article Cancer Vaccines in Cancer Treatment is owned by David Olle. Permission to republish Cancer Vaccines in print or online must be granted by the author in writing.
|
|
|
|
