Immunologic Escape and Immunotheraphy

Immunologic Escape and Immunotheraphy

Immunologic Escape and Immunotheraphy

In spite of immune surveillance, tumors occur in normal individuals because tumor cells escape destruction. Several theories are put to explain this immunologic escape. For instance, (i) individuals learn to tolerate tumor cells before' immune competence has developed and then express the tumor later in life, (ii) that majority of cancer cells are destroyed by killer cells, but that rapidly growing variants emerge and outpace the immune system, (iii) that tumor antigens elicit antibodies that protect against the killer cells, (iv) that tumor cells release substances that suppress the immune system.

None of these theories is universaily accepted. Immunotherapy for the management of cancer is developing along several lines. It includes (i) injection of the killer lymphocytes specific for the tumor, or monocolonal antibodies for tumor antigens be injected. (ii) use of interferon to enhance the activity of natural killer cells. In 1986, interferon was used against hairy cell leukatm1ia, cancer of white blood cells named for the hairlike appendages on malignant cells, (iii) use of interleukin 2, a T-lymphocyte protein (a lymphokine), began in 1985. This protein stimulates the rapid multiplication of the cell that produced it as well as other helper T-lymphocytes. (iv) the use of another anti-cancer agent, the tumor necrosis factor (TNF), a protein product of macrophages discovered in 1975. TNF is currently produced by genetic engineering and is shown effective against 20 kinds of cancer cells grown in culture.

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