Identification of human mononuclear cells by anti-monocyte serum

An antiserum to human leukaemic monocytes was raised in rabbits. Adsorption with human thymocytes and chronic lymphatic leukaemia cells rendered the antiserum specific for cells of the human myeloid and monocytic cell series. Additional adsorption with granulocytes left a weak, but specific, activity for monocytes. The cells in normal peripheral blood with which the antiserum reacts by an immunoperoxidase technique have typical monocyte morphology. Cells with typical lymphocyte morphology do not react with the antiserum, but a few cells with intermediate morphology were also stained by the antiserum. Using the antiserum as a marker, the precursor cells of the monocytic and myeloid cell series were traced in the bone marrow.