It is believed that any person who lives long enough will eventually get cancer. In the past, cancer was thought to be invincible. More recently traditional treatments have been supplemented with newer treatments like chemoprevention and cancer vaccines.
The immune system has developed to protect the body against invasion by microorganisms and prevent disease. As more information about immune cells is discovered, scientists have realized that the immune system plays a crucial role in preventing cancer. The implication of this finding is that, by designing cancer vaccines, it is possible to boost the immune system to enable it to combat cancer more effectively.
Traditional vaccines have successfully prevented infectious diseases like small pox. Recently, great progress has been made in the development of vaccines against cervical cancer, caused by human papilloma virus. However, vaccine development of other types of cancers poses more challenges, since most cancers are believed not to be caused by infectious agents, but rather, defects in cellular proteins. Since these proteins are very similar to those found in normal cells, it is difficult to develop vaccines targeting the cancer cells while sparing normal cells. Indeed, most cancer vaccines will be useful for treating cancers in patients already afflicted and not for preventing cancers. The concept of a universal vaccine against cancer is not realistic since there are many types and many causes of cancers.
To learn how cancer vaccines work it is essential to start with insight into the working of the immune system. This review begins with a primer on tumor immunology: the identity and role of each cell involved in recognizing and fighting cancer. The next section explains how tumors actively try to evade the immune system, while the concluding section highlights the strategies used in designing cancer vaccines.
REVIEW SUMMARY
Immunology Primer
The immune system can be divided into two branches; both are involved in fighting cancer.
Innate: Barriers that human beings are born with, including special cells, to fight specific bacteria and other invaders. Natural killer cells are the most significant innate cells that fight cancer directly.
Adaptive: Response that the immune system generates to fight threats as they occur. Lymphocytes are cells involved in fighting these threats. There are two types of lymphocytes, B cells and T cells. Some lymphocytes are cells that trigger immunity, while other lymphocytes are memory cells that allow this adaptive response to occur repeatedly. Cytotoxic T cells are the adaptive cells that directly fight cancer. However, they cannot always recognize cancers and need antigen-presenting cells, dendritic cells, to help them do so.
Properties of Tumors
-Since they resemble normal cells, tumors tend not to trigger the immune system.-Tumors also actively evade the immune system in different ways.
-Immune cells are not very efficient in detecting tumor growth.
Cancer Vaccines
-Vaccines boost the immune system.
-Preventive vaccines may be used to prevent cancers induced by viruses, such as cervical cancer.
-Most cancer vaccines will probably be therapeutic, used for patients who already have cancer.
-Cancer vaccines modify the immune system response to evoke a strong and specific immune response.
-Types of cancer vaccines include: - Tumor antigens used to familiarize the body against the cancer; Monoclonal antibodies to mimic tumor antigens; Stimulation of the cytotoxic T cells to fight the cancer
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