Tumor necrosis factor receptor superfamily member 11B (TNFRSF11B) is also known as Osteoclastogenesis inhibitory factor (OCIF), Osteoprotegerin (OPG). TNFRSF11B is a secreted homodimer protein, which can interact with TNFSF10 and TNFSF11. TNFRSF11B acts as decoy receptor for TNFSF11/RANKL and thereby neutralizes its function in osteoclastogenesis. TNFRSF11B inhibits the activation of osteoclasts and promotes osteoclast apoptosis in vitro. Bone homeostasis seems to depend on the local ratio between TNFSF11 and TNFRSF11B. TNFSF10/TRAIL binding blocks the inhibition of osteoclastogenesis.