The frequent failure of attempts to treat metastatic cancer may stem in part from the heterogenous nature of malignant neoplasms which leads to the rapid emergence of metastases resistant to conventional therapy (JAMA [MEDICAL NEWS] 1982;247:417).
However, observes Isaiah J. Fidler, DVM, PhD, there now is "evidence that activated macrophages can recognize and destroy neoplastic cells in vitro without regard to their phenotypic diversity."
As a result, a number of laboratories are investigating the mechanisms by which macrophages destroy tumor cells, ways in which this process can be enhanced, and the best ways to incorporate macrophage therapy into conventional anticancer treatments. These investigations have utilized a wide array of in vitro, animal, and clinical systems, although none of the macrophage-enhancing protocols are yet ready for large-scale use in patients, nor is it probable that they will be for some time.
The "mononuclear phagocyte" system of the human body consists of