Species differences in the immunophenotype of osteoclasts and mononuclear phagocytes

Human osteoclasts, in contrast to mononuclear phagocytes, are known to express a well-defined restricted range of myeloid antigens. To determine whether these antigenic differences are present in other species, we examined the immunophenotype of chicken and rabbit osteoclasts, macrophages, macrophage polykaryons, and monocytes and compared them with similarly derived and cultured human cells. Human, rabbit, and avian osteoclasts reacted with monoclonal antibodies against human beta 1 integrins (CD29, CD49b, CD49d), beta 3 integrins (CD51, CD61), as well as human macrophage-associated antigen CD68. Avian osteoclasts also reacted for CD11a/18 and CD14 which are not present on human osteoclasts. Avian and mammalian monocytes, macrophages, and macrophage polykaryons expressed all the above antigens. Both avian and human macrophage polykaryons produced by culture of peritoneal macrophages reacted with anti-CD51 antibodies indicating that expression of the vitronectin receptor alone does not distinguish between these cells in vitro.