antibody or an antigen binding fragment of the antibody, pharmaceutical composition, uses of at least one of the antibody or antigen binding fragments and of a transformed host cell composition, polynucleotide, vector, and
Provided is a pharmaceutical composition for the treatment and/or prophylaxis of abnormal bone metabolism targeting a protein encoded by a gene strongly expressed in osteoclasts. Specifically provided is a pharmaceutical composition containing an antibody which specifically recognizes human Siglec-15 and has an activity of inhibiting osteoclast formation, and the like.