Identification and Characterization of a Differentiation Antigen in Human

Human promyelocytic leukemia (HI-GO) cells were induced to differentiate into macrophage-like cells by treatment with i0 mol/L 1,25-dihydroxyvitamin D3 (VD3). A monoclonal antibody (MoAb, 60B8), reactive with the particulate of the differentiated cells but not of the untreated cells, was isolated. The antigen recognized by the MoAb became apparent two days after VD3 treatment. and its concentration increased and peaked on day 6. Human neutrophils, followed by monocytes and differentiated HL-60 cells, showed the greatest abundance of the antigen. Monocytes cultured for eight days in vitro lost the antigen. No 60B8 antigen was seen in other blood cells. The MoAb precipitated two polypeptides with an apparent molecular weight (mol wt) of 15,000 (15 k) and 13 k in the detergent-