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Immune
System Overview In the field of cancer research exists a category called biological response modifiers or BRM’s for short. BRM’s are agents designed to mobilize the body’s own defense mechanisms against disease; in this case, cancer. Most of the work in this area has centered on enhancing the ability of the immune system to identify and destroy cancers (neoplasms). In order to conceptualize the potential and problems associated with BRM’s, we must look at some of the components of the immune system. A key concept in understanding BRM’s concerns the ability of the immune system to respond to the antigen. This is referred to as immunogenicity. In employing BRM’s against cancer, the challenge has been that most human tumors exhibit high antigenicity, but low immunogenicity, partly due to their ability to evade detection.
MHC: MHC stands for major histocompatibility complex. MHC’s are present on the surface of all of our cells and when all is well they say hey this tissue is me this is self don’t destroy me I’m you! The MHC on the surface of the cell will express not only self, but also pieces of the viruses or abnormal proteins such as might be found in cancer cells. Cytotoxic T-cells (CD-8) can recognize antigens in this context if they have had previous exposure to the particular antigen. In such a case they will start sending signals (cytokines, lymphokines) to the rest of the immune system saying, we have an invader. Later, we’ll describe what happens after that. When an infected cell, virus or other pathogen is ingested by a macrophage, specific pieces of the invader are displayed on the macrophages cell surface along with information about the host. In this context, the present material is referred to as MHC 2. Helper T-cells can only respond to MHC 2, in other words, the antigen must be ingested by a macrophage or other antigen-presenting cell first, presented on the cell surface, and then read by the Helper T cell. Then, the T-helper cell begins to activate other components of the immune system. One of the main lymphokines secreted by the T-helper cell is IL-2. It is important to understand the role of MHC, because defects in the way MHC is presented on the cell surface allow many cancers to evade detection. One role of biological response modifiers (BRM’s) is to help the immune system recognize cells, which are becoming cancerous. Fortunately, one type of lymphocyte does not need to see MHC. In fact when it does not see MHC on the surface of a cell (remember that MHC identifies the cell as self) it knows something is wrong. This cell is the natural killer cell (NK). Because many cancerous cells do not display MHC, NK cells are vitally important in the immune response to cancers. Scientists have attempted to help the immune system by administration of chemical messengers such as IL-2 and certain interferon’s. Often these therapies are plagued with side effects. The good news is that emerging research is demonstrating ways to use these chemical messengers with minimal side-effects. Immune Therapies International is actively researching in this area. If you are technically minded, there is an excellent overview of tumor immunology here. |
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"Alternative Cancer Treatments"
Michael Guthrie,
R.Ph. CGP 2003-2006
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Though an oversimplification, we can visualize the immune system as having two
main components: cell-mediated immunity, and humoral-mediated (antibody)
immunity. Cell mediated immunity is the term used to describe any immune
response in which phagocytic or cytotoxic cells play the main role. In
cell-mediated immunity the cells of primary importance in cancer are
macrophages, T-cells (Helper, Cytotoxic and Suppressor) and natural killer cells
(NK).