CD34 and leukemia: CD133 but not CD19 is expressed on normal primitive fetal hematopoietic stem cell/multipotent progenitors (Lin–CD34+CD38–), while fetal B-progenitors (CD34+CD19+) express CD19 but not CD133, confirming that CD133/CD19 coexpression is leukemia-specific (supplemental Figure 1D).