Natural killer cells play a central role in the fight of the immune system against infected or tumorigenic cells. On their search for, e.g., cancer cells the killer cells also encounter other cell types, in particular uninvolved or bystander cells. Now scientists of the SFB 1027 found out that the presence of these bystander cells does not impede the efficiency of the killers in their search for cancer cells. On the contrary, the efficiency was increased, which was totally unxpected. The reason for this boost is the secretion of radical oxygen species (ROS) by the bystanders. This study is a prime example for a successful collaboration between experiment and theory and involved 4 research groups of the SFB 1027: Bin Qu (project A2), Heiko Rieger (project A3), Volkhard Helms (project C3), and Ivan Bogeski (project C4). The results were now published in Scientific Reports.