Description: The TKS-1 monoclonal antibody reacts with mouse 4-1BB Ligand (4-1BBL), a type II transmembrane protein and a member of the tumor necrosis factor superfamily. 4-1BBL is expressed by activated antigen presenting cells including B cells and macrophages. Interaction of 4-1BBL with 4-1BB (CDw137) is reported to deliver a costimulatory signal important in the T-APC interaction.