Induction of Human Osteoclast‐like Cells by Treatment of Blood Monocytes with Anti‐Fusion Regulatory Protein‐1/CD98 Monoclonal Antibodies

We have developed a new and simple system of human osteoclast formation by fusing peripheral blood monocytes with anti‐Fusion Regulatory Protein‐1 (anti–FRP‐1) monoclonal antibody (mAb). When human blood monocytes were cultured in the presence of anti‐FRP–1/CD98 mAbs, polykaryocytes began to appear at approximately 15 h and increased in size with time until 3–4 days of incubation with anti–FRP‐1 mAb. These fused cells showed positive staining in tartrate‐resistant acid phosphatase, possessed numerous calcitonin receptors, and were capable of bone resorption. These results strongly suggest that anti–FRP‐1 antibody‐induced multinucleated cells are osteoclasts. Furthermore, FRP‐1 antigens were detected in osteoclasts isolated from human bone and in the osteoclast‐like cells obtained from human giant cell tumors of bone.