Rat Anti-Mouse 4-1BBL (CD137L) Antibody (TKS-1)

4-1BBL (CD137L, TNFSF9) is a type II transmembrane glycoprotein belonging to the tumor necrosis factor (TNF) superfamily that serves as the cognate ligand for the 4-1BB (CD137) receptor, a costimulatory molecule expressed on activated T cells, natural killer (NK) cells, and dendritic cells (DCs). Primarily expressed on antigen-presenting cells (APCs) including mature DCs, B cells, macrophages, and endothelial cells, 4-1BBL engages with its receptor in a trimeric configuration to deliver potent costimulatory signals that promote T cell survival, proliferation, cytokine production (particularly IFN-γ), and enhanced cytotoxic activity, while also activating NK cells and DCs to amplify anti-tumor immune responses. This interaction plays a critical role in sustaining T cell immunity during chronic antigen exposure and has emerged as a promising therapeutic target in cancer immunotherapy, with agonistic antibodies targeting the 4-1BB/4-1BBL axis being developed to enhance T cell function in solid tumors and hematological malignancies, as well as being incorporated into chimeric antigen receptor (CAR) T cell designs to improve persistence and efficacy.