Characterization of cancer stem cell markers in Brca1 cell lines. Cell lines A1.1, B1.15, P2.1 and P3.17 were stained with fluorescently-conjugated mAb specific to CD44 (A), or CD24 (B), in parallel with isotype control-matched mAb and analyzed by flow cytometry. In the histograms shown, the thick black line represents positive staining and the gray filled lines represent the isotype control-matched mAb. (C) Bivariate plots represent the double staining of cell lines with fluorescently-conjugated CD44 and CD24 mAb. The quadrants are gated based on isotype controls and separate the double positive, single positive, and double negative populations. The percent of positive fraction for single label and CD44+/CD24- cells after compensation are indicated in each panel.