Monocyte-mediated growth control and the induction of tumor cell death.

In the present article a hypothesis is put forward and supporting data are referred that explain the elimination of tumorigenic cells as a consequence of their failure to comply with the rules of ubiquitous negative growth control mechanisms involving among others also mononuclear phagocytes as effector cells. This hypothesis does not invoke the recognition of altered cell surface structures on tumorigenic cells as the basis for discriminating them from normal cells and thus avoids one of the most irritating problems of hypothetical tumor defense mechanisms involving the recognition of spontaneously arising tumor cells as 'non-self' by immunologic effector cells.