AC133 expression on fetal liver cells. Fetal liver mononuclear cells were stained with AC133PE (vertical axis) and CD34FITC (horizontal axis) as described. CD34^bright/AC133⁺ cells are seen in region R2. The gates R1 and R2 are representative of those used in selection of bone marrow CD34/AC133 subpopulations for in vitro colony assays.