Immune system agents

Advances in immunology during the last part of the twentieth century have continued at a rapid rate and cytokines and immune cells having specific markers continue to be defined. A number of natural and synthetic immunotherapeutic agents have been discovered that can modulate components of the normal or aberrant immune system, through stimulation or suppression. However, most of these substances also have inherent adverse side effects. 

Secondary immunodeficiencies (9) are much more common than primary ones and frequently occur as a result of immaturity of the immune system in premature infants, immunosuppressive therapy, or surgery and trauma. Illnesses, particularly when prolonged and serious, have been associated with secondary immunodeficiencies, some of which may be reversible. Acquked immune deficiency syndrome (AIDS) (10—12) may be considered a secondary immunodeficiency disease caused by the human immunodeficiency vimses HIV-1 or HIV-2. Hitherto unknown, the disease began to spread in the United States during the latter part of the 1970s. The agent responsible for this infection has been isolated and identified as a retrovims. 

Chinese Herbal Medicines. Many traditional Chinese medicines have been screened for radioprotective activity in experimental animals. In one study of more than a thousand Chinese herbs, a number of agents increased the survival rate of dogs exposed to a lethal dose of y-rays by 30—40%, and some symptoms of radiation injury were ameHorated. These effects are potentially related to stimulation of the hemopoietic and immune systems (130). Extracts of five Chinese dmg plants, as weU as aspirin, effectively protected mice exposed to 7.5—8.0 Gy (750—800 rad) of y-radiation, and increased survival rates by 8—50% (131). Several Chinese traditional medicines, adininistered ip before or after irradiation, protected against Hpid peroxidation in a variety of mouse tissues, including BM, Hver, and spleen, as weU as in mouse Hver microsomal suspensions irradiated in vitro (132). 

Immunosuppressive agents (immunosuppressants) are drugs that attenuate immune reactions. An application is indicated in case our immune system reacts inadequately leading to serious diseases or normal immune reactions are unwanted, e.g., following transplantations. 

Unit X discusses drugp that affect the immune system. The unit consists of two chapters immunologic agents and antineoplastic drugs. 

Immunologic Toxicity—The occurrence of adverse effects on the immune system that may result from exposure to environmental agents such as chemicals. 

IFNs are natural glycoproteins produced by the cells of most vertebrates in response to the challenge by foreign agents, such as infectious organisms (viruses, bacteria, fungi, and parasites), and by tumor cells. IFNs can be produced by cells of the innate and adaptive immune systems and by non-immune cells such as fibroblasts and epithelial cells. 

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