A monoclonal antibody (NAT-9 II:3F-6F) that identifies a differentiation antigen on human myeloid cells

A monoclonal antibody, designated NAT-9 II:3F-6F (IgM), was generated by hybridization of mouse myeloma cells with spleen cell from mice immunized with normal human bone marrow cells. The antibody reacted with 40-60% of bone marrow cells as analysed on samples from 40 normal individuals and only with a subpopulation of human acute myeloid leukemia (AML) cells of the M2 class (20/20 tested) and M4 class (12/12 tested) (subclasses of the French-American-British (FAB) classification), but not with leukemic cells of the M1 (0/12 tested) and M5 (0/12 tested) FAB subclasses. This is in contrast to many other myeloid-specific monoclonal antibodies. Fluorescence-activated cell sorter (FACS) analyses and morphological examination of cells stained with peroxidase as based on the NAT-9 II:3F-6F monoclonal antibody showed that this antibody reacted with a distant differentiation antigen which is absent on myeloblasts, but expressed on promyelocytes, myelocytes, metamyelocytes, band neutrophils, and on a minority of mature granulocytes. NAT-9 II:3F-6F did not bind to circulating monocytes, T and B cells, erythrocytes and a variety of different human cell culture lines. Immunoblotting demonstrated that the antibody bind to a cellular component with a Mr approximately 97.400 dalton. The antibody may be useful in immunological subclassification of non-lymphoid leukemias and in studies on hematopoiesis.