This volume will center on the BLyS(BAFF) family of ligands and receptors. It will be divided into sections based on topics covering both basic and translational/clinical aspects of this molecular family's biology. It will focus heavily the BLyS family's role in the differentiation, selection, and regulation of primary and antigen-experienced B cells. Additional sections will cover clinical aspects of this family, including its association with autoimmunity and neoplasia, current thinking about the mechanistic basis for these associations, and the potential of BLyS family members as therapeutic targets. In addition, how BLyS family members play roles in other cell types may be included.