antibody or functional antibody fragment, pharmaceutical composition, use of an antibody or functional fragment thereof, polynucleotide, vector, and transformed host cell.
Provided is a pharmaceutical composition for treating and/or preventing 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.