PURPOSE: Fc receptors and Mac-1 play an important role in the protective response of granulocytes and monocytes against microbial infection. FcgammaRl, FcgammaRll, FcgammaRlll as well as CD11b/ CD18 have never been measured in a quantitative way during hemopoiesis. Thus we quantified the expression of Fc Rl, Fc Rll, Fc Rlll, and CD11b/CD18 during hematopoietic differentiation using HL-60 cells, which was induced to differentiate by DMSO, or PMA. METHODS: HL-60 cells (ATCC CCL-240) were induced to differentiate by adding 1.0% DMSO, or 16nM PMA. On the 4th and 7th day after stimulation as well as before stimulation, phenotypic analysis was performed by flow cytometry after staining the cells with PE-conjugated anti- human CD64, CD32, CD16, CD11b, CD18, and isotype controls. And the measured fluorescent intensity was transformed into Molecules of Equivalent Soluble Fluorochromes (MESF). RESULTS: Percent positive cells and MESF of CD11b on HL-60 cells increased upon induction by DMSO, but not by PMA. Percent positive cells of CD18 on HL-60 cells was 99% regardless of differentiation. But MESF of CD18 was increased on the 4th day and decreased on the 7th day by DMSO or PMA. Percent positive cells and MESF of FcgammaRl on HL-60 cells increased upon induction by DMSO or PMA. Percent positive cells of FcgammaRll on HL-60 cells was above 90% regardless of differentiation. MESF of FcgammaRll showed no significant change by DMSO or PMA. CONCLUSION: Quantitative expression of FcgammaRl, FcgammaRll, FcgammaRlll, and CD11b/CD18 of HL-60 cells changed during induction of differentiation by DMSO or PMA. MESF of FcgammaR and CD11b/ CD18 a better indicator than percent positive cells to compare the differentiation of HL-60cells.