Expression of Fas and FasL in unilineage erythroid differentiation. Purified peripheral blood CD34⁺ cells were cultivated with high concentration of Epo and very low amounts of IL-3 and GM-CSF for up to 14 days. (A) After 7 and 14 days cells were stained with control, anti-Fas (Fas), and anti-FasL (FasL) Abs, and analyzed by flow cytometry. (B) Semiquantitative RT-PCR analysis from erythroblasts at different days of culture and from HuT78 cells. Top lane, human FasL cDNA amplification; bottom lane, GAPDH cDNA amplification used to normalize RT-RNAs. A representative experiment out of three performed with cells from different donors is shown.