IMMUNOLOGICAL RESPONSES TO AFLATOXINS AND OTHER CHEMICAL CARCINOGENS

Human populations are exposed to a large variety of natural and synthetic chemical compounds in air, water and food. Cancer, which has become one of the most frequent causes of death today in many parts of the world, may have environmental etiology. Previously, cancer incidence was thought to be more frequent in developed countries than in the developing ones. However, developing countries are quickly catching up with the developed ones, as the present data indicate. Some of the important chemical carcinogens present in our environment are mycotoxins, polycyclic aromatic hydrocarbons, various solvents, pesticides, metals, synthetic harmones, food colours and food additives. Most cancers result from a complex interaction between multi-environmental and endogenous factors, and carcinogenesis is regarded as mediated through a multistep process. Further, it is possible that various chemical carcinogens help in expression of 'oncogene' which otherwise remains repressed. A majority of carcinogenic compounds have been shown to induce immunosuppressive effects. Immunosuppression has been found in high proportion in cancer prone families and patients. Increased metastasis and enhanced growth of tumors have been reported in immunosuppressed animals. Malnutrition may predispose the host to severe immunosuppression and thus facilitate the development of cancer. It has been found that a malnourished host is more susceptible to toxicity and carcinogenicity caused by various chemicals including aflatoxins. Recently, the use of immunomodulators has become more and more helpful in the treatment of autoimmune diseases, immune deficiency, severe infection and malignancies. Treatment with the immunomodulators reverses the immunosuppressed condition and produces immunopotentiation in the cancer bearing host. Attempts are being made throughout the world to prevent or control cancer by this approach.