TNFSF15 is a type II transmembrane protein which is predominantly expressed in endothelial cells. It has a single transmembrane domain, a small cytoplasmic domain and an extracellular C-terminus. Its expression is stimulated by TNFA and IL1A. TNFSF15 acts as the ligand for the receptor protein TNFRSF25 which is primarily found in activated T cells. It also has an affinity to the decoy receptor protein TNFRSF6B. Binding of this cytokine to its receptor can activate the transcription factor NF-Kappa-B and MAP Kinases. It has been found that TNFSF15 can also induce apoptosis by acting as an autocrine factor and inhibit endothelial cell proliferation. Recombinant Human TNFSF15 herein refers to the secreted form of the protein.