Fas and FasL expression in bone marrow erythroblasts. Bone marrow erythroid cells obtained by needle aspiration were purified by Ficoll and flow cytometry sorting based on glycophorin-A positivity. Erythroblasts were subsequently analyzed by flow cytometry for Fas and FasL expression (A), and by immunohistochemistry on cytospins stained with control (B) or anti-FasL polyclonal Abs (C) and revealed with alkaline phosphatase. A representative experiment out of five performed with cells from three different donors is shown.