Neoplastic disease and tumor immunology from the perspective of host-parasite relationships.

Neoplasia is considered within the biologic framework of host-parasite relationships, and the arguments favoring this perspective are discussed. By viewing neoplastic processes as dynamic interactions between transformed clones, host defense mechanisms, and the environmental circumstances impinging directly on the neoplastic event, the experimentalist and clinician are better prepared conceptually for a balanced assessment of all factors determining the development and outcome of confrontations with neoplastic clones. The frame of reference placing progressive neoplasia into the category of host-parasite associations also prepares the ground for techinical approaches to the study and observation of oncologic phenomena appropriate to their essential nature. The correct evaluation and most promising future development of the current emphasis on immunologic parameters of neoplasia demands especially an awareness of the role of immunologic variables in other host-parasite relationships.