Molecular mechanisms for activated macrophage recognition of tumor cells.

The biological heterogeneity of tumor cells requires a therapeutic modality that recognizes and kills resistant as well as susceptible tumor cells but does not harm normal cells. Tumoricidal macrophages appear to be able to fulfill these criteria. The mechanisms by which macrophages recognize tumor cells are not known, but they recognize carbohydrates and proteins that may be relevant for binding to tumor cells. In addition, phospholipids appear to be involved in the macrophage-tumor cell interaction. The abnormal presence of phosphatidylserine (PS) on the outer leaflet of tumor cells correlates with enhanced binding and cytotoxicity by macrophages.