BAFF Human Active Protein

The protein encoded by this gene 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/BAFFR. 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. Alternatively spliced transcript variants encoding distinct isoforms have been identified. [provided by RefSeq, Mar 2011]

Function: Cytokine that binds to TNFRSF13B/TACI and TNFRSF17/BCMA. TNFSF13/APRIL binds to the same 2 receptors. Together, they form a 2 ligands -2 receptors pathway involved in the stimulation of B- and T-cell function and the regulation of humoral immunity. A third B-cell specific BAFF-receptor (BAFFR/BR3) promotes the survival of mature B-cells and the B-cell response. Ref.5 Ref.16Isoform 2 seems to inhibit isoform 1 secretion and bioactivity

By similarity. Ref.5 Ref.16Isoform 3:Acts as a transcription factor for its own parent gene, in association with NF-kappa-B p50 subunit, at least in autoimmune and proliferative B-cell diseases. The presence of Delta4BAFF is essential for soluble BAFF release by IFNG/IFN-gamma-stimulated monocytes and for B-cell survival. It can directly or indirectly regulate the differential expression of a large number of genes involved in the innate immune response and the regulation of apoptosis. Ref.5 Ref.16

Subunit structure: Homotrimer. Isoform 2 heteromultimerizes with isoform 1, probably limiting the amount of functional isoform 1 on the cell surface. Isoform 3 is unlikely form trimers or bind to BAFF receptors. Ref.4 Ref.5

Subcellular location: Cell membrane; Single-pass type II membrane protein. Tumor necrosis factor ligand superfamily member 13b, soluble form: Secreted.

Tissue specificity: Abundantly expressed in peripheral blood Leukocytes and is specifically expressed in monocytes and macrophages. Also found in the spleen, lymph node, bone marrow, T-cells and dendritic cells. A lower expression seen in placenta, heart, lung, fetal liver, thymus, and pancreas. Isoform 2 is expressed in many myeloid cell lines. Ref.4

Induction: Up-regulated by exposure to IFNG/IFN-gamma. Down-regulated by phorbol myristate acetate/ionomycin treatment.

Post-translational modification: The soluble form derives from the membrane form by proteolytic processing.Isoform 2 is not efficiently shed from the membrane unlike isoform 1

By similarity.N-glycosylated.

Sequence similarities: Belongs to the tumor necrosis factor family.