7C3, a marker for the differentiation of human macrophage cell lines

The induction of differentiation in the human monoblastlike cell line U937 by 1,25 dihydroxyvitamin D3, interferon gamma, or phorbol esters is associated with the expression of a novel surface antigen, 7C3. The expression of 7C3 is maximal after 24 hr and is dependent upon de novo protein synthesis. The appearance of 7C3 during U937 differentiation is inhibited by dexamethasone while the increased expression of the macrophage marker OKM1 is not affected. 7C3 antigen is also expressed on HL60 cells when induced along the macrophage pathway and is expressed weakly on peripheral blood monocytes but not on lymphoid cells or granulocytes. 7C3 expression is sensitive to trypsin and low concentrations of the nonionic detergents NP-40 and Triton X-100. The induction of 7C3 expression may serve as a useful model to understand the regulatory events involved during the early phases of monocyte-macrophage differentiation.