Cells expressing CM retain CD34 expression and have aberrant differentiation potential. (A-C) Proliferating cells from normal CB samples (3-5 weeks in culture) or from long-term CM cultures (3 different clones, weeks 13-16 in vitro) were magnetically purified for CD34⁺ cells. Weekly thereafter cells were stained for (A) differentiation markers, (B) CD34, or (C) a lineage cocktail (week 4 only). Error bars indicate the SD of the 3 independent experiments.