Myeloid differentiation antigen defined by a monoclonal antibody

A monoclonal antibody of the IgM kappa type directed at a determinant on K-562 cells was produced and characterized. This hybridoma antibody, provisionally termed D5, defines a membrane-associated antigen that seems to be restricted, within the hemopoietic system, to the granulocytic cell lineage and possibly also to very immature erythroid and monocytic cells. Within the granulocytic cell lineage, D5 antibody reacts with all differentiation stages starting from the promyelocyte up to and including the mature granulocyte. Normal and malignant myeloblasts are only weakly positive or negative. Within the monocytic cell lineage, only fairly immature malignant cells as represented by cells from two patients with monoblastic leukemia and by two monoblastoid cell lines were found to be strongly D5 positive. Among the mature glass-adherent lmonocytic cells from normal peripheral blood, only very few cells react with D5 antibody. The fact that we have raised this antibody against cells (K-562) that are considered to represent very immature erythroid precursor cells would suggest that normal erythroid precursors should also be D5 positive. However, so far we are unable to detect such cells. Therefore, the proportion of D5-positive erythroid precursors resembling the K-562 cell type must either be very low in the bone marrow, or the D5 antigen is not present on normal erythroid precursor cells and only aberrantly expressed on K-562 cells. Mature erythrocytes are also D5 negative. There was no evidence that lymphoid precursors react with D5 antibody, in that all normal and malignant lymphoid cells tested so far were D5 negative. Further, platelets showed no reactivity with D5 antibody.