The function of ENSG00000181634 (TNFSF15, TNF superfamily member 15) is as follows. Cytokine that signals through TNFRSF25 receptor (PubMed:11911831). Functions as a T-cell costimulator, that increases IL-2 responsiveness and secretion of proinflammatory cytokines which enhances T-cell activation, proliferation and the survival of activated T-cells (PubMed:10597252, PubMed:11911831). Inhibits vascular endothelial growth and angiogenesis (in vitro) (PubMed:11923219, PubMed:9872942). Binds to the decoy receptor TNFRSF6B, blocking the activation normally triggered by TNFSF15 and leading to decreased T- cell activation and reduced inflammation (PubMed:21300286). {ECO:0000269|PubMed:10597252, ECO:0000269|PubMed:11911831, ECO:0000269|PubMed:11923219, ECO:0000269|PubMed:21300286, ECO:0000269|PubMed:9872942}.