Simultaneously four different laboratories identified a new member of the tumor necrosis factor (TNF) family. This has been named as TALL-1 (6), THANK (TNF homologue that activates apoptosis, nuclear factor-kappaB, and c-Jun NH2-terminal kinase (5), BAFF (for B cell activating factor belonging to the TNF family) (4) and BLyS (B lymphocyte stimulator) (3). Membrane-bound BLyS (BAFF) is processed and secreted through the action of a protease whose specificity matches that of the furin family of proprotein convertases. Secreted BLyS (BAFF) acts as a potent B cell growth factor. This protein is expressed abundantly in peripheral blood lymphocytes, specifically in monocytes and macrophages. BLyS (BAFF) regulation is upregulated by interferon gamma. Overexpression of BLyS (BAFF) in transgenic mice lead to increased numbers of mature B and effector T cells. These mice also develop autoimmune –like symptoms, such as high levels of rheumatoid factors, anti-DNA autoantibodies, etc. (2). Two receptors for BLyS (BAFF) have been identified and termed as BCMA and TACI (1).
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