BAFF is a cytokine that belongs to the tumor necrosis factor (TNF) ligand family. This cytokine is a ligand for receptors TNFRSF13B/TACI, TNFRSF17/BCMA, and TNFRSF13C/BAFF-R. This cytokine is expressed in B cell lineage cells, and acts as a potent B cell activator. It has been also shown to play an important role in the proliferation and differentiation of B cells. It is expressed as a membrane-bound type II transmembrane protein on various cell types including monocytes, dendritic cells and bone marrow stromal cells. Interaction between BAFF and BAFF-R activates classical and noncanonical NF-κB signaling pathways. This interaction triggers signals essential for the formation and maintenance of B cell, thus it is important for a B-cell survival.