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