Immunocytochemical characterization of monocyte colonies of human bone marrow: a clue to the origin of Langerhans cells and interdigitating reticulum cells.

Human bone marrow was cultured and cells from individual monocyte colonies stained with a variety of polyclonal and monoclonal antibodies. Erythroid colonies and peripheral blood monocytes were used as controls. Both bone marrow cultured and peripheral blood monocytes stained with antibodies to lysozyme, non-specific cross reacting antigen (NCA) and alpha-1-antitrypsin and the cells stained variably for HLA-DR. A small number of cells in each cultured bone marrow colony stained with antibody to human thymic antigen (HTA T6) and most of the cells stained with variable intensity using anti-S-100 protein. No cells reactive with these two antibodies were detected in peripheral blood monocyte preparations and erythroid colony cells were negative for all antigens studied. The presence of cells within individual bone marrow colonies with phenotypic properties of both phagocytic macrophages (lysozyme positive, NCA positive, alpha-1-antitrypsin positive) and Langerhans cells/interdigitating reticulum cells (HTA(T6) positive, S-100 protein positive) suggests that these cells share a common stem cell and are both components of the mononuclear phagocyte system.