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The treatment of cancer by improving the ability of a tumor-bearing individual (the host) to reject the tumor immunologically. There are molecules on the surface of tumor cells, and perhaps in their interior, that are recognized as different from normal structures by the immune system and thus generate an immune response. The two components of the immune response are cell-mediated and antibody-mediated immunity, which must work in concert to overcome tumor cells. One type of thymus-derived lymphocyte (also called a cytotoxic T cell) can destroy tumor cells directly, while another recruits other white blood cells, the macrophages, that do the killing. Natural killer cells and perhaps other white blood cells may also participate. However, elements that normally regulate immunity, such as suppressor T cells, are stimulated excessively by the tumor, which leads to an immune response that is deficient and unable to reject the growing tumor. Thus the strategy of immunotherapy is to stimulate within or transfer to the tumor-bearing individual the appropriate antitumor elements while avoiding further stimulation of suppressor elements. See Cellular immunology, Immunologic cytotoxicity, Immunosuppression
There are four broad categories of immunotherapy: active, adoptive, restorative, and passive. Active immunotherapy attempts to stimulate the host's intrinsic immune response to the tumor, either nonspecifically or specifically. Nonspecific active immunotherapy utilizes materials that have no apparent antigenic relationship to the tumor, but have modulatory effects on the immune system, stimulating macrophages, lymphocytes, and natural killer cells. Specific active immunotherapy attempts to stimulate specific antitumor responses with tumor-associated antigens as the immunizing materials. Adoptive immunotherapy involves the transfer of immunologically competent white blood cells or their precursors into the host. Bone marrow transplantation, while performed principally for the replacement of hematopoietic stem cells, can also be viewed as adoptive immunotherapy. Restorative immunotherapy comprises the direct and indirect restoration of deficient immunological function through any means other than the direct transfer of cells. Passive immunotherapy means the transfer of antibodies to tumor-bearing recipients. This approach has been made feasible by the development of hybridoma technology, which now permits the production of large quantities of monoclonal antibodies specific for an antigenic determinant on tumor cells. See Genetic engineering, Immunology, Monoclonal antibodies
a branch of practical immunology concerned with the treatment of infectious diseases through the use of immunological preparations, such as vaccines, immune sera, and gamma globulins.
Sera and gamma globulins are used for acute types of disease, such as diphtheria, tetanus, botulism, and cerebrospinal meningitis. Vaccines are injected for protracted, sluggish, and chronic forms of infection, such as dysentery, brucellosis, and tularemia. Immunotherapy is combined with antibiotics and chemotherapy.
In veterinary medicine, infectious diseases are treated by injecting affected animals with therapeutic sera and bacteriophages. When injected with therapeutic serum or the gamma globulin obtained from it the animal receives, in ready form, protective substances (antibodies) against the causative agent of the disease or its toxin.