Characterization of purified fetal and adult nucleated erythroid cells. (A) Wright-Giemsa–stained fetal liver and adult marrow cells before and after purification by ficol density gradient and anti-glycophorin-A–conjugated magnetic beads. (B) Percentage of glycophorin-A (CD235a)–positive cells before and after purification. (C) Relative levels of globin gene mRNA in purified cells from fetal and adult erythroid cells determined by quantitative RT-PCR. Results are normalized to the geometric mean of β-actin and G3PD mRNAs as described in “Materials and methods; Quantitative RT-PCR and Hb HPLC.” Values are plus or minus 1 standard deviation. (D) Hb HPLC patterns from purified fetal liver and adult erythroid cells.