Regulation of B-cell-activating factor (BAFF)/B lymphocyte stimulator (BLyS) expression in human neutrophils.

The expression and production of cytokines by cells of the innate immune system, including monocytes/macrophages, dendritic and NK cells, play a critical role not only in defensive and inflammatory but also in immunoregulatory and anti-/pro-tumoral processes. Studies performed in the last years have well ascertained that polymorphonuclear neutrophils can also be induced to express and produce chemokines, proinflammatory, anti-inflammatory, immunoregulatory, angiogenic and fibrogenic cytokines, as well as ligands belonging to the TNF superfamily. Among the latter group of molecules, B-cell-activating factor (BAFF)/B lymphocyte stimulator (BLyS), known to be essential for B lymphocyte homeostasis and related pathologies, has recently been identified as one of the factors potentially expressed by human neutrophils. The addition of this novel TNF superfamily member, and more recently also of the closely related "A Proliferation-Inducing Ligand" (APRIL), to the list of cytokines produced by neutrophils not only testifies to the continuous growth of this area of investigation, but also implies the involvement of neutrophils in B-cell-dependent autoimmune diseases and tumors.