The strategies for immunotherapy that have evolved as a result of at least partial understanding of tumor antigens and the host immune response to cancer include the use of cytokines, vaccination against tumors, monoclonal anti-tumor associated antigen antibodies, and adoptive cellular immunotherapy. Various species of interferon, interleukin-2, tumor necrosis factor, IL-4 and IL-1 are being examined for their therapeutic effects, to directly inhibit tumor cell growth in some cases, but also because of their pleiotropic effects on the immune system. Tumor vaccine development was based first on the notion that since a variety of tumors express tumor associated antigens, tumor vaccines using even crude products might stimulate specific immunologic reactivity leading to resistance against tumor growth. These products included inactivated whole tumor cells or crude subcellular fractions of tumor cells. More recent approaches have exploited the development of genetically modified tumor cells containing genes encoding various cytokines - thus rendering the inoculated tumor cells considerably more immunogenic.
Another area of intense clinical interest is adoptive cellular therapy. This cancer treatment method has re-emerged as a potentially powerful treatment strategy. It is based on the premise that various lymphocytic effector cells can recognize and mediate cytotoxic and other effects against tumor cells. Adoptive cellular therapy is aimed at generating large numbers of these effector cells and transferring them to the tumor-bearing host. The emphasis of most studies has been on the use of lymphocyte activated killer (LAK) cells or tumor infiltrating lymphocytes (TIL), both relying on incubation of effector cells with IL-2 to expand the number of immunocompetent lymphocytes.