Human RANKL (receptor activator of NF-kB ligand), known as Trance (TNF-related activation-induced cytokine receptor) and OPGL (Osteoprotegerin ligand), or CD254, is a type II transmembrane protein in TNF superfamily that has two forms-a membrane-anchored protein and a secreted protein. Its extracellular domain is related to TRAIL, FasL, and TNF. TRANCE is expressed on osteoclasts and activated T cells. It has been implicated in the regulation of the interactions between T cells and dendritic cells. RANKL plays an important role in osteoclast differentiation and bone resorption. Trance activates JNK and NF-kappaB and induces the expression of IL-1, IL-6, IL-12, IL-15 in dendritic cells.