CD33 and acute lymphoblastic leukemia: This data, together with previous work from several laboratories using other maturation-dependent antigens, including CD34, CD10 and CD20, support the notion that high-risk MLLr-B-ALL does not follow a stem cell hierarchy in pediatric/infant B-ALL.8, 9, 11 Recent findings from Vormoor laboratory support our data as they found that NG2 was not expressed in MLLr CD34+CD38− hematopoietic stem cells but was upregulated in differentiated CD33+ and CD19+ MLLr acute myeloid leukemia and ALL blasts.49, 50