Quantitative determination of transformed cells in a mixed population by stimultaneous fluorescence analysis of cell surface and DNA an individual cells.

Cell-surface labeling with fluorescamine indicates that the fluorescence of Balb 3T3 A31 cells in considerably decreased after both viral and chemical transformation. This phenomenon, coupled with the technique of flow microfluorometry, enabled nontransformed and transformed cells to be distinguished. A second fluroescent probe, propidium iodide, which intercalates into DNA, was used in combination with fluorescamine in order to obtain a ratio of cell-surface labeling to DNA content. This manipulation allowed enhanced resolution of two populations and the detection of small numbers of transformants in a predominantly normal population.