Flow cytometric detection of human blasts (CD45+/CD19+ for B-ALL and CD45+/CD5+ or CD45+/CD7+ for T-ALL, based on surface marker phenotyping in the original tumor material) showed engraftment in all but one (patient #0031) patient sample, resulting in an engraftment rate of 94.4%. This evidence concerns the gene PTPRC and acute lymphoblastic leukemia.