Tumor Immunology

Tumor Immunology

Tumor Immunology

The change from a normal cell to a cell with tumor potential is accompanied by several physiological changes. Tumor cells contain antigens not found in surrounding cells. These antigens may induce an immune response and make the cancer cells vulnerable to destruction. However, the cells escape the resistance mechanisms of the body and proliferate to form the tumor. As the tumor breaks apart and spreads, a metastasizing cancer develops. Four types of antigens have been indentified in tumor cells. One type, called oncofetal antigen occurs in certain tumors as well as in fetal tissues.

An example is aplha fetoprotein (AFP), an antigen found in embryonic development and several cancers, especially of liver. Another example is carcinoembryonic antigen (CEA) also found in fetal tissues as well as cancer of the colon. The second type of antigen is found in tissues transformed by chemical carcinogens. The third and fourth types of antigens are those associated with DNA viruses and RNA viruses respectively. Host resistance to tumors depends immune responses directead against the tumor antigens. This process is termed immune surveillance. It is considered an ongoing function of killer T -lymphocytes which recognise the antigens as foreign and destroy the cells containing them in a way similar to graft rejection. Another cell thought to function in immune surveillance is the natural killer (NK) cell, that exerts a nonspecific. Cytotoxic effect against other cells, including tumor cells.

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