The antitumor immune response as a problem of self-nonself discrimination: implications for immunotherapy.

Much evidence now exists that tumors possess specific antigens recognizable by T cells. The goal of immunotherapy is to break tolerance to these antigens while preserving self-tolerance. Recently, newer approaches have been developed in animal systems that modify tumor cells genetically so that they express new antigens or secrete certain cytokines. Engineering tumor cells to secrete cytokines in a paracrine fashion can induce powerful local cytokine effects which, in addition to inducing local inflammation, can alter the presentation of tumor antigens or the activation of tumor-antigen-specific T lymphocytes, resulting in systemic antitumor immunity.