Fig. 5. CD34 and MTS24 identify distinct subpopulations of basal keratinocytes with high in vitro replicative capacity. (A,B) Keratinocytes harvested from dorsal epidermis of adult C57Bl/6 mice were sorted under sterile conditions. (A) Flow cytometric analysis shows that CD34+ basal keratinocytes are members of a different population of cells than the MTS24+ keratinocytes. Sorted 6 single+, 6+/MTS24+, 6+/CD34+ or the unseparated mixture (all sorted) keratinocytes colonies were grown for 14 days to visualise the colonies (B) and compare relative colony-forming efficiency (C). (D) Individual colonies from 6+/MTS24+ and 6+/CD34+ keratinocytes were passaged and replated at clonal density for an additional 14 days. (E) A graphical comparison of the size of colonies derived following passage. Bars represent the mean of at least four replicate culture wells±s.e.m. Data are shown from representative experiments that were repeated with similar results.