In the June 11 issue of Cell, Kraus et al. (2004) show, through conditional mutagenesis, that mature B cells have a drastically reduced life span in the absence of normal B cell antigen receptor (BCR) surface expression or tonic signal transduction. These studies support a role for signal transduction downstream of the BCR, rather than continued surface expression per se for the maintenance and survival of mature B cells in the periphery. Further, these studies exclude transient INFγ-induced activation as a prerequisite to apoptosis in receptor-less cells.