Abstract
There is considerable evidence that the initiation and growth of tumor masses can be modulated by the immune system. This influence not only applies to the primary tumor burdens, but is also apparent in the establishment and development of metastases. Several immunologic components are involved in these processes, however, the relevance of the cell-mediated compartment has been amply documented. The interactions among regulatory, helper, and effector cells are undeniably important, however, in many instances, the direct actions of several types of immune cells with lytic potential represent an important aspect of tumor immunology. Using animal models of breast cancer and, on a smaller scale, clinical experimentation, much information has been generated in several laboratories, providing insight into the relative contributions of various types of cytotoxic effectors operative against mammary tumors. Our understanding of the function of such cells in the context of in vivo tumor development is a first step in devising logical protocols for immu-notherapeutic approaches.