Portending death in germinal centers - when B cells know their time is up.

B cells undergo stringent selection in germinal centers (GCs) for expression of high-affinity antibodies, however, mechanisms of negative selection of low-affinity B cell clones remain elusive. A new study by Michel Nussenzweig's group published in Science leverages a new reporter system that marks pre-apoptotic GC B cells to dissect microanatomic regions of GCs and their role in affinity maturation.