ASP expression in CD34 positive cells obtained from MPB samples gated according to cell size into small, intermediate, and large. Region R6 identifies weak CD34 positive cells expressing the ASP-protein, and region R7 identifies strong CD34 positive cells expressing the ASP-protein. Three-color immunofluorescence staining was performed. After staining of membrane antigens with anti-CD34-tri-color and anti-CD38-PE antibodies, cells were permeabilized with Ortho Permeafix, stained with anti-ASP-FITC, and analyzed on the FACScan.