Cancer and the immune system
The immune system attacks and eliminates not only bacteria and other foreign substances but also cancer cells. A cancer cell is a cell not strange, it is a cell whose biological function has been altered so that does not meet the body’s normal mechanisms that control the growth and reproduction of it. The abnormal cells can continue to grow, turning into cancer.
In the immune system, a large part of the body’s defense against cancer is carried out directly by cells, rather than by antibodies circulating in the blood. For example, the presence of tumor antigens on cancer cells can activate certain white blood cells (lymphocytes and in a much lesser degree, monocytes) which perform an immune surveillance seeking and destroying cancer cells.
The primary role of the immune system to control the development of a cancer cell is exemplified by a startling statistic: Cancer is 100 times more likely to occur in people who take drugs that suppress the immune system (eg, because of transplant of an organ or a rheumatic disease) than in those with normal immune systems. Also, sometimes a transplanted organ is a cancer that was not diagnosed before transplantation. The cancer could have been growing very slowly or may not have grown at all in the donor organ. However, it begins to grow and spread rapidly in the transplant patient, whose immune system is nullified by the drugs supplied to protect the transplant. In general, when drugs that decrease the immune response are suspended, the transplanted organ is rejected and transplanted cancer is also destroyed.
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