Figure 1.

Fractionation and colony-forming ability of neonatal primary human foreskin basal epidermal cells on the basis of α₆ integrin expression. (A) Flow cytometric analysis of freshly isolated basal keratinocytes stained with either an anti-α₆ mAb (4F10; solid line) or isotype control mAb (1A6.11; broken line) detected by a FITC-conjugated secondary antibody. Two fractions representing the upper 30% (R6) α₆^bri cells and the lower 30% (R7) α₆^dim cells were collected by FACS and cultured. (B) Colony numbers obtained from 5,000 UF, α₆^bri, and α₆^dim cells. Keratinocyte colony numbers were determined after 2 weeks in culture by staining with toluidine blue after removal of the feeder layers. The α₆^bri fraction consistently gave rise to greater colony numbers than the α₆^dim fraction, indicating that the α₆^bri fraction was enriched for colony forming cells. These results are typical of several replicate experiments (n = 5).