Figure 2.

Characterisation of CD24^High, CD24^Low and CD24^Negative populations. (a) Cell populations sorted on the basis of CD24 expression were stained for cytokeratin (CK)8/18 or CK14. The mean percentage of CK14 and CK8/18 positive cells (±standard deviation) and the total number of cells counted is indicated for each population. Results from four independent sorts. (b) Cells were double stained with CK14 and CK8/18. Only CK18⁺/CK14^- cells were observed in the CD24^High population (top panel). The majority of CD24^Low cells were CK14⁺, with occasional CK18^-/CK14^- cells (bottom panel, inset). No CK18⁺/CK14⁺ cells were observed. Scale bar = 75 μm. (c) Quantitative rtPCR reactions were carried out to determine fold changes in expression of a selection of genes with known luminal epithelial (Ltf, Mfge8, Krt1-18), myoepithelial/basal (Krt1-14, Myl6a) or non-epithelial (Myl6a, Procollagen 3a1 (Col3a1), CD31) distribution, compared to leucocyte-depleted, bulk mammary cells. The analysis was carried out on two independent cDNA syntheses from each of three independent sorts (CD24^Low and CD24^High) or on two independent cDNA syntheses from one sort and a single cDNA synthesis from a pool of two further sorts (CD24^Negative). Significance levels are indicated by: *P < 0.05; **P < 0.01; ***P < 0.001.