What's new in macrophage-tumor cell interaction?

Macrophages--alone or interacting with other host defense elements--can modify the tumor growth, which usually means a process ending with tumor-cell killing, but in some instances may promote tumor progression. The knowledge on the actual capacity of host extra- and/or intratumoral macrophages to be activated by different kinds of biological modifiers or other effector cells, is necessary in order to design effective immun-manipulation in cancer patients. Progression of malignant tumors can be considered as the outcome of innumerable interactions between tumor cells and host cells with a clear indication on the failure of host defense. Host defense against tumors represents a complex series of interrelated specific and non-specific reactions of different cell types including macrophages. There is little doubt that macrophages--at least in vitro--can effectively destroy tumor cells by cytolytic mechanism, although in few instances their supportive effect on tumor growth is also documented. All of these events require the activation of macrophages.