Monocyte/macrophage-specific monoclonal antibody Ki-M1 recognizes interdigitating reticulum cells

A monoclonal antibody, Ki-M1, was produced, and its immunoreactivity was tested by light and electron-microscopic immunohistochemistry. Ki-M1 was found to react with monocytes, cells of the mononuclear phagocyte system (MPS), interdigitating reticulum cells (IDC), and the so-called indeterminate dendritic cells of lymphoid tissue. No reactivity was seen in other human tissues or other hematopoietic cells, including granulocytes and cells of the unstimulated promyelocyte cell line HL-60. Thus, Ki-M1 is the first of the monoclonal antibodies to MPS cells to react with both human IDC and MPS cells. This suggests that IDC and MPS cells may have a common cytogenesis.