PROBLEM TO BE SOLVED: To provide a substance which inhibits differentiation maturation and activity of an osteoclast targeting a protein encoded by a gene expressed strongly in the osteoclast, as well as to provide a pharmaceutical composition for the treatment and/or prevention of bone metabolism disorder.SOLUTION: The invention provides an antibody or a functional fragment of the antibody which specifically recognizes and binds to human Siglec-15 polypeptide consisting of amino acid residues in positions 39-165 of a specific amino acid sequence, and inhibits formation of a human osteoclast and/or bone resorption by human osteoclasts, and a pharmaceutical composition which is a treating or preventing agent of bone metabolism disorder and contains at least either one of the antibody or the functional fragment of the antibody. The antibody is a chimeric antibody, and is humanized, wherein the heavy chain comprises a constant region of human immunoglobulin G double chain, and the light chain comprises a constant region of human immunoglobulin &kgr； light chain.【課題】破骨細胞で強く発現する遺伝子にコードされる蛋白質を標的として、破骨細胞の分化成熟と活性を阻害する物質並びに、骨代謝異常治療及び／又は予防用医薬組成物の提供。【解決手段】特定のアミノ酸配列の３９～１６５番目アミノ酸残基からなるヒトＳｉｇｌｅｃ－１５ポリペプチドを特異的に認識して結合し、ヒト破骨細胞の形成及び／又はヒト破骨細胞による骨吸収をを抑制する抗体又は該抗体の機能性断片、該抗体又は抗体の機能性断片の少なくともいずれか一つを含有する、骨代謝異常の治療及び／又は予防剤である、医薬組成物。キメラ抗体であり、ヒト化されており、重鎖がヒト免疫グロブリンＧ２重鎖の定常領域を含み、軽鎖がヒト免疫グロブリン鼬ｙ鎖の定常領域を含む抗体【選択図】なし
