It is clearly demonstrated that the day 70 CD19+ fraction has a great overlap with specifically up and down regulated genes in t(4;11) infant leukemia patients (74% overlap of upregulated genes, 71% overlap of downregulated genes), as well as in t(4;11) non-infant leukemia patients (86% overlap of upregulated genes, 70% overlap of downregulated genes). This evidence concerns the gene CD19 and leukemia.