Cutting edge: B cell receptor signals regulate BLyS receptor levels in mature B cells and their immediate progenitors.

This study examines how B lymphocyte stimulator (BLyS) receptor expression and responsiveness are influenced by B cell receptor (BcR) signaling. Our results show that resting and BcR-stimulated B cells are dependent on BLyS for survival and that B cells remain BLyS responsive during BcR-induced activation. Further, BcR ligation up-regulates expression of the BLySR B cell maturation defect/BLySR3 (Bcmd/BR3), but not other known BLySRs. Finally, the coupling of BcR signaling with Bcmd/BR3 expression is limited to late transitional and mature B cells. Together, these findings establish the coupling of BcR signaling with Bcmd/BR3 expression as a fundamental aspect of follicular B cell selection, survival, and activation.