title: Monoclonal antibodies against osteoclasts inhibit bone resorption in vitro.
abstract: Several recently-derived monoclonal antibodies (mcabs) that bind with a high degree of specificity to membrane antigens of osteoclasts were tested for their effects on the function of giant cells from osteoclastomas. None of the antibodies stimulated bone resorption when incubated with giant cells on bone slices, nor did we find any evidence that the mcabs were able to block calcitonin-inhibition of bone resorption. However, three of the mcabs strongly inhibited bone resorption. This inhibition was unaccompanied by impaired survival or morphological evidence of toxicity, but the same mcabs induced a state of cytoplasmic quiescence we have previously found to be characteristic of the response of osteoclasts to local and systemic inhibitors of osteoclastic bone resorption. These results suggest that the mcabs bind to antigens of functional importance in bone resorption or its regulation, and the similarity between the response of giant cells to mcabs and hormonal inhibitors of bone resorption raises the possibility that the mcabs may bind to and cause activation of surface receptors for one or more of these hormones. Whether this is so or not, the mcabs which influence giant cell function may represent valuable probes for an analysis of the mechanism and regulation of osteoclastic bone resorption.
mesh_terms: D000911:Antibodies, Monoclonal; D001862:Bone Resorption; D003593:Cytoplasm / Q000502:physiology; D005870:Giant Cell Tumors / Q000503:physiopathology; D006801:Humans; D066298:In Vitro Techniques; D010010:Osteoclasts / Q000276:immunology / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal