The Eagle Biosciences Free soluble RANKL ELISA Assay Kit is an enzyme immunoassay for the quantitative determination of free, soluble, uncomplexed human RANKL in serum or heparin plasma. The Eagle Biosciences Free soluble RANKL ELISA Assay Kit is for research use only and not to be used in diagnostic procedures. Sample Types: human serum, heparin plasma. Range: 0 to 2 pmol/l. Sensitivity: (0 pmol/l + 3 SD): 0.01 pmol/l / 0.008pmol/l. Time: 3.5 hours ? RANKL, the receptor activator of nuclear factor kappa B ligand, a member of the tumor necrosis factor (TNF) family, is the main stimulatory factor for the formation of mature osteoclasts and is essential for their survival. RANKL activates its specific receptor RANK, located on osteoclasts and dendritic cells. The effects are counteracted by OPG which acts as an endogenous soluble receptor antagonist (see: BI-20403 - OPG ELISA). The major source of RANKL are osteocytes, former osteoblasts that become embedded within the mineralized bone matrix. RANKL is a ~35 kD type II transmembrane-type protein and is cleaved to release a soluble biologically active product that forms a homotrimer. RANKL and its specific receptor RANK are not only key regulators of bone remodeling but also play an essential role in immunobiology, e.g. lymph node formation, establishment of the thymic microenviroment, mammary gland development during pregnancy, bone metastasis in cancer and sex-hormone, progestin-driven breast cancer, thermoregulation, and finally in the development of type 2 diabetes mellitus.