Discrimination of Human Macrophages and Dendritic Cells by Means of Monoclonal Antibodies

Two monoclonal antibodies (MoAb), RFD1 and RFD7, have been used to investigate whether human macrophages and dendritic cells represent phenotypically distinct cell types. RFD7 recognizes a 77 kd antigen, and is specific for acid phosphatase positive tissue macrophages, while RFD1 recognizes a unique Class II antigen, which is associated with dendritic cells. With immunohistological/cytological methods it was found that neither of these reagents reacted with granulocytes, monocytes, or lymphocytes, with the exception that a small proportion (<20%) of B cells were stained with RFD1. In tissues, RFD7 reacted with mature macrophages only and did not stain Langerhans cells in the skin or the interdigitating (dendritic) cells of the T-cell zones of lymphoid tissue and the thymic medulla. Conversely, RFD1 appeared specific for the interdigitating (dendritic) cells and did not react with macrophage populations identified morphologically, geographically, and histochemically in any tissue studied. When peripheral blood monocytes (RFD1−, RFD7−) were matured in vitro, two distinct populations of RFD1+ RFD7− and RFD7+ RFD1− cells emerged. It is concluded that in normal tissues these two reagents identify phenotypic differences between macrophages and dendritic cells that may have functional significance.