Alterations in phenotype and cell-surface antigen expression levels of human monocytes: differential response to in vivo administration of rhM-CSF or rhGM-CSF.

We investigated, via multicolor flow cytometry, the in vivo effects of colony-stimulating factors (CSFs) on cell size, frequencies, and expression of surface antigens on peripheral blood monocytes from melanoma patients treated concurrently with CSFs and tumor-specific monoclonal antibody (mAb) R24. Recombinant human macrophage colony-stimulating factor (rhM-CSF) increased cell size, relative percentages of monocytes, percentages of CD14+, HLA-DQ+, CD11b+, and CD16+ monocytes, and cell-surface expressions of HLA-DR and CD11b; rhM-CSF also up-regulated cell-surface expression of CD14 on CD14brightCD16- monocytes. Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) increased cell size, percentages of CD14+, HLA-DQ+, and CD11b+ monocytes, and cell-surface expressions of HLA-DR, HLA-DQ, CD11b, and CD58. Relative percentages of monocytes and CD16+ cells and cell-surface expression of CD14 on CD14brightCD16- monocytes decreased. In addition, monocytes derived from patients treated with rhM-CSF showed functional activity when assayed in vitro for antibody-dependent cellular cytotoxicity (ADCC). During treatment and coincident with increased CD16 expression, monocytes derived from rhM-CSF patients had enhanced levels of cytotoxicity towards melanoma target cells compared to healthy controls and to patients treated with rhGM-CSF.