Novel proteins and polypeptides binding to osteoclastogenesis inhibitory factor (OCIF) (OCIF-binding molecules, OBMs) and nucleic acids encoding these proteins and polypeptides are provided. Processes for producing these proteins, polypeptides, and nucleic acid molecules by genetic engineering are provided. Medicinal compounds are provided which comprise proteins and nucleic acids according to the invention, as well as proteins which bind to OBM, including anti-OBM antibodies. These compounds may be used for the treatment of bone disease.