To determine the role of DuAb and EDuAb in specifically mediating CD19+ malignant cell lysis by human primary T cells, ALL or lymphoma cell lines (Nalm6, Namalwa) and CD19 negative control cell line (K562), were cocultured with human primary T cells in the presence of varying concentrations of DuAb and EDuAb. This evidence concerns the gene CD19 and acute lymphoblastic leukemia.