A study of Natural Killer Cells~Samples were taken at the time of diagnosis and then cultivated with NK cells. Certain patients' NK cells did not react at all. In contrast, the NK cells in other patients went about serious work indicating that they had very active immune systems. 12 years later almost half of the patients whose NKs had not reacted in the laboratory had died. On the other hand, 95% of those whose immune systems had been active were still alive.