The giant cells recruited by subcutaneous implants of mineralized bone particles and slices in rabbits are not osteoclasts.

We have compared structural and functional characteristics of native osteoclasts and the multinucleated giant cells (MNGC) recruited by subcutaneous implants of mineralized bone particles and slices in normal rabbits. Weekly evaluation of the implants for 5 weeks showed distinct differences between MNGC and osteoclasts in the host with respect to morphology and the ability to stain for tartrate-resistant acid phosphatase and acid ATPase. An osteoclast-specific monoclonal antibody bound strongly to osteoclasts but not MNGC. Ground bone slices similarly implanted were surrounded by MNGC but did not show resorption pits by scanning electron microscopy. These data show that the MNGC recruited to subcutaneous implants of mineralized bone particles and slices lack the enzymatic, cell surface, and functional features of osteoclasts.