Receptor Activator of NF-kappa B Ligand (RANKL) is a cell-bound marker (CD254) related to the TNF family of Proteins. RANKL plays a critical role in bone metabolism, particularly osteoclast differentiation. In addition, RANKL is expressed by some T cells is thought to promote dendritic cell matu ion. Recombinant soluble RANKL is a non-glycosylated Protein, containing 176 amino acids, with a molecular weight of 20 kDa.