Immune Response to Tumors: Tumor Antigens and Antitumor Immunity

So let’s turn now away from tumors of the immune system itself, and ask the question - does the immune system naturally prevent or attack cancers? Well the answer is yes, but perhaps only for certain cancers. So what is the evidence that the immune system can actually recognize and attack cancers. Well there’s an increased incidence of certain cancers in patients with immunodeficiency, including immunosuppressed transplant patients as we’ve just mentioned. The term immunosurveillance is used. And this relates to the concept that cells of the immune system patrol around the body looking for cells that have become abnormal because of malignant transformation. Certainly the immune system can prevent tumors that are linked to oncogenic pathogens. And it’s now known that a number of organisms can trigger the development of tumors. So for example, the virus HTLV1 (Human T-cell Leukemia Virus-1) as the name suggests, is responsible for inducing T-cell leukemia. Epstein-Barr virus can trigger a number of tumors including Burkitt’s lymphoma, nasopharyngeal carcinoma and post-transplant lymphoma. The Human Papilloma viruses 16 and 18 are responsible for triggering cervical cancer and penile cancer. Hepatitis B virus and Hepatitis C virus are linked to the development of liver cancer. And the bacterium Helicobacter pylori can trigger the development of stomach cancer. So it’s quite clear in these kind of situations where infectious agents are linked to the development of a tumor. And after all the immune response has developed, has evolved to fight infectious agents. One can see a clear potential role for the immune system in this kind of situation. The term tumor antigen is used to describe antigens that are associated with tumor cells. Remember, tumors are derived from normal cells. Tumor-associated antigens are antigens that are present either in or on normal cells. And the immune system...