First, the NK cell recognizes and binds to the cancer cell. This process requires receptor-to-receptor interaction. Next, the NK cell releases granules which penetrate the cancer cell and ultimately kill it. The NK cell is then free to bind to another cancer cell and repeat the same process. However, cancer cells know how to fight back in a sort of cell war. We found for the first time in our laboratory that cancer cells can destroy WBCs through the phenomenon of phagocytosis. We have observed three ways in which this is done. The cancer cell can extend two arms around the WBC or it can develop a cup-shaped opening where the WBC is drawn inside. A third way is for the cancer cell to extend a long arm to capture the WBC and finally draw it inside the cancer cell where it is digested. In addition, extensive work by others has shown that cancer cells secrete immune-suppressive substances which inhibit the function of the immune system. Many attempts have been made in the last 25 years to strengthen the power of the immune system using different biological response modifiers (BRMs). These are substances originating from bacteria and fungi which possess immunoaugmentory properties. In addition, some kinds of cytokines serve as BRMS such as interferons, interleukin-2 and interleukin-12.  There are two problems associated with these BRMS: 1st) toxicity and 2nd) the development of hyporesponsiveness in which a single administration of the BRM can significantly enhance NK cell activity, but that repeated administration of the same BRM results in depression of NK cell activity.  It is interesting to note that MGN-3 has advantages over other BRMs. It is nontoxic and has not shown hyporesponsiveness in the four years that the patients have been followed. This work was undertaken in order to investigate the augmentory effect of a new BRM known as MGN-3 on NK cell function and T and B cell proliferation in 32 patients. Tumor-associated antigens were reported for selected patients.