Monoclonal antibody (mAb) to the RANK receptor was generated using Hybridoma technology, as previously performed in our laboratory (13, 14) . Briefly, 6-8-week-old female BALB/c mice were immunized intraperitoneally three times with 25 μg of recombinant human sRANK receptor (Peprotech, USA) on days 0 and 14 using complete and incomplete Freund's adjuvant, respectively, and once with 10 μg of antigen on day 28 using phosphate-buffered saline (PBS, pH 7.3). The immune response to the antigen was assessed by measuring the titer of polyclonal antibody in mouse serum using an indirect enzyme-linked immunosorbent assay (ELISA). Mice with the highest antibody titer were euthanized and splenectomized 3 days after the final injection of antigen. Spleen cells were fused with SP2/0 myeloma cells at a ratio of 4:1 using 50% (w/v) polyethylene glycol (PEG) (Sigma, USA) according to the technique described previously by Köhler & Milstein (15) . The hybridoma cells were suspended in culture medium (RPMI 1640) supplemented with penicillin, streptomycin, L-glutamine (PSG), hypoxanthine aminopterin thymidine (HAT), and 20% fetal bovine serum (FBS) (Sigma, USA). Cells were seeded in 96-well tissue culture plates and incubated in a humidified 37°C, 5% carbon dioxide incubator for 2 weeks. Clones were maintained in HAT medium for a further 2 weeks.