Homeostatic niche specification among naïve and activated B cells: a growing role for the BLyS family of receptors and ligands.

B lymphocyte homeostasis encompasses the establishment and maintenance of independently regulated niches, within which cells compete for viability promoting resources. The BLyS/BLyS receptor family controls the size and composition of these niches, by governing the selection and survival of most peripheral B cells. Moreover, different receptor-ligand sets from this family dominate the regulation of various B cell subsets. These observations suggest a model whereby the regulation of BLyS receptors by differentiative and stimulatory cues yield characteristic BLyS receptor signatures, thus specifying homeostatic niche and competitive advantage.