Analysis of expression of human mammary epithelial antigens in normal and malignant breast cells at the single cell level by flow cytofluorimetry.

The expression of cell-type specific antigens on the surface of human mammary epithelial cells (HME antigens) is analyzed at the single cell level by flow cytofluorimetry. Methods are described to deal with two technical difficulties that have hampered the quantitation of surface antigens on cells from primary cultures by flow cytofluorimetry, namely, cell clumping and the presence of several cell types. By staining the cells simultaneously with two different fluorescent markers: the cell surface HME antigens with fluorescein-tagged antibodies (green fluorescence) and the cell DNA with propidium iodide (red fluorescence), it was possible to determine the expression of HME antigens per unit DNA, analyze their expression on breast cells in mixed populations, and analyze their expression in different phases of the cell cycle. The HME antigens were diminished in malignant breast epithelial cells as compared to their normal counterpart.