4-1BB Ligand (4-1BBL, also CD137L) is a 32kD type II transmembrane protein that belongs to TNF superfamily (TNFSF) of molecules. The human 4-1BBL cDNA encodes a 254aa (aa) protein that contains a 25aa N-terminal cytoplasmic domain, a 23aa transmembrane segment, and a 206 aa C-terminal extracellular region. 4-1BBL is expressed by activated B cells, macrophages, dendritic cells, activated T cells, neurons and astrocytes. A 26kD soluble form of 4-1BBL is known to occur in human. Although it is presumably generated by MMP activity, its aa size is currently unreported. The soluble form is bioactive. Human 4-1BBL signals through both CD137/4-1BB and itself. Its cytoplasmic tail participates in reverse signaling that induces apoptosis in T cells and cytokine secretion (IL-6, TNF-alpha) by monocytes. 4-1BBL binding to CD137/4-1BB produces a number of effects. Its seems to play a key role in the T cell recall response. It maintains T cell numbers at the end of a primary response, and induces CD4 and CD8 T cells to proliferate and secrete cytokines such as IL-2 and IFN-gamma in CD4 cells, and IFN-gamma in CD8 cells. Applications: Suitable for use in Flow Cytometry. Other applications not tested. Recommended Dilution: Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4C before opening. DO NOT FREEZE! Stable at 4C as an undiluted liquid. Dilute only prior to immediate use. Stable for 12 months. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. Freezing APC conjugates will result in a substantial loss of activity. APC conjugates are sensitive to light.
