Receptor activator of nuclear factor x03BA;B (RANK) and its ligand (RANKL) have originally been described for their key roles in bone metabolism and the immune system. Subsequently, it has been shown that the RANKL-RANK system is critical in the formation of mammary epithelia in lactating females and the thermoregulation of the central nervous system. RANKL and RANK are under the tight control of the female sex hormones estradiol and progesterone. RANKL/TNFSF11/CD254 Protein, Human, Recombinant (His & Flag) is expressed in HEK293 mammalian cells with N-His-Flag tag. The predicted molecular weight is 22.6 kDa and the accession number is O14788-2.