Distinct appearance of differentiation markers in HL60 cell line treated with 1,25 dihydroxyvitamin D3 and phorbol esters (TPA).

Peripheral blood monocytes are comprised of a heterogeneous population of cells with respect to phenotype and functional activity. In this investigation we confirm the presence of two distinct subsets of peripheral blood adherent monocytes with respect to MHC class II antigens HLA DR and HLA DQ using two color FACS analysis. In the attempt to mimic the in vivo situation promyelocytic cells lines have been established which can be induced to undergo characteristic monocytic differentiation in response to a variety of agents. The HL 60 cell line can be induced in vitro by phorbol esters (TPA) to display membrane HLA DR and HLA DQ antigens along with the mature monocytic marker Leu M3. Physiological concentrations of 1,25 dihydroxy Vitamin D3 leads to the expression of HLA DR and Leu M3 antigens but not HLA DQ. These data suggest that these inducers may cause the differentiation of phenotypically distinct monocytic subpopulations.