Natural Killer Cell in Action (1 of 2) (IMAGE) Imperial College London Caption This light microscope image shows a white blood cell (left) assessing whether or not another cell is diseased. Credit Bjorn Onfelt and Dan Davis Usage Restrictions None 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.