CD33 and CLEC12A are highly expressed in pediatric AML and widely absent in both healthy hematopoietic and nonhematopoietic tissue. (A) Percentage of leukemic blasts, defined as CD45^dim cells within the initial BM of an AML patient (n = 28-36; see also supplemental Figure 1A), expressing 1 of 11 surface molecules (mean ± standard deviation [SD]). Gating of flow cytometry was performed using isotype control antibodies. (B) Percentage of leukemic blasts and healthy hematopoietic progenitors (CD45^dim cells within healthy BM; see supplemental Figure 1A) expressing 1 of 8 selected surface molecules (mean ± SD). (C) MFI ratio of 11 surface molecules on leukemic blasts. Because results are from multicolor flow cytometry, quantitative comparison between target antigens using different fluorochromes allows only limited semiquantitative analysis. (D) MFI ratio of 8 selected surface molecules on pediatric AML blasts and healthy hematopoietic progenitors. (E) Expression of 11 surface proteins analyzed in this study and 4 more genes found to be overexpressed in pediatric AML (CD7, P2RY13, CD244, and ITGB5) in healthy tissues using the ProteomicsDB^26,27  repository. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as ubiquitously expressed gene and CD19 as suitable immunotarget for B-cell precursor ALL are depicted in green. Genes are clustered according to similar expression patterns.