The FAB PLA Method (image) University of Freiburg Caption On resting cells (A) the B cell antigen receptors form groups and the nano ruler emits red signals (cell staining below). After activation of the B cells by an antigen the red signal disappears (B). The kinase Syk mediates the opening of the receptor. Credit Michael Reth Usage Restrictions the image may only be used with appropriate caption or credit 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.