Cell surface antigens on osteoclasts and related cells in the quail studied with monoclonal antibodies

The properties of five monoclonal antibodies raised against isolated osteoclasts are described. Osteoclasts were isolated from medullary bone of egg-laying female quails. Mice were immunized with cell preparations consisting for about 10% of multinucleated osteoclasts. A large number of monoclonal antibodies against cell surface antigens were obtained, five of which were extensively characterized by their interactions with different tissues of the quail and their cross-reactivity with other species. Two monoclonals (OC 5.3 and OC 6.8), recognize surface antigens present on osteoclasts, monocytes, granulocytes and endothelial cells, but not on osteoblasts, osteocytes, fibroblasts, lymphocytes, erythrocytes and others. The three other monoclonal antibodies are specific for multinucleated osteoclasts in bone tissue but recognize some cell surface structures in other tissues. Antibody OC 6.9, which in bone tissue stains primarily the surface area of the osteoclast that is adjacent to the resorbing bone surface, also interacts with bile capillaries in the liver and with specific, but not yet identified parts of the nephron. The antibodies OC 6.1 and OC 6.3 interact with Kupffer cells in the liver and tissue macrophages of small intestine. In view of the possible fallacies inherent to the use of cell surface markers for the demonstration of cell relationship and origin, definite conclusions can not yet be made. The fact that the osteoclast, the Kupffer cell and the intestine macrophage are the only cells in bone, bone marrow, liver, kidney and intestine, that share the same surface antigen recognized by monoclonals OC 6.1 and OC 6.3, suggests, however, a common origin for osteoclasts and a number of well described tissue macrophages.