Abstract
Monoclonal antibodies were raised against normal human bone marrow cells. One of the antibodies obtained, monoclonal antibody 3C4 (MA 3C4), the subject of this paper, was characterised by immunofluorescence studies with viable normal peripheral blood and bone marrow cells and by immunoperoxidase studies using paraffin sections. In bone marrow and peripheral blood MA 3C4 reacts selectively with cells of late neutrophilic granulopoiesis (myelocytes, metamyelocytes, and neutrophilic granulocytes). Cells of erythropoiesis, thrombopoiesis and lymphopoiesis are negative. In lymph node and spleen only neutrophils react with MA 3C4. In non-haemic tissue reactivity was seen with epithelial cells of a variety of different gland ducts. Thus the antigen detected by MA 3C4 can serve as a marker for neutrophil differentiation in normal haemopoiesis and as a marker for ductal epithelial cells of a variety of organs within non-haemic tissue. The antigen is formalin-resistant and can be detected in paraffin sections. The antibody thus appears to be a valuable reagent for both haematological research and for routine pathology.