NK Cells (IMAGE) St. Jude Children's Research Hospital Caption The new screening approach developed by St. Jude involves identifying donors who make the most potent version of specialized immune cells called natural killer (NK) cells. Illustrated is an NK cell destroying a cancer cell. Credit Joshua Stokes, St. Jude Children's Research Hospital Usage Restrictions Use image with appropriate caption and credits. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.