Natural Killer Cells are the most aggressive white cells in the immune system. They make up about 5% to 15% of the total lymphocyte circulating population. They target tumor cell and protect against a wide variety of infectious microbes. Natural Killer Cells are a very important factor in the fight against cancer. Immune Stimulation is the key to keeping the white blood cell count high and giving the Natural Killer Cells a chance to fight cancer and other diseases.