Once Killer Cells (Red) (image) University of Bonn Share Print E-Mail Caption When you get wind of an infection, they convene a kind of team of various immunocytes (green or yellow). Only in this microenvironment are they fully activated. Credit © AG Kastenmüller/Universität Bonn Usage Restrictions This photo may be used with the press release. Share Print E-Mail 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.