One population was characterized by a typical early T-cell precursor acute lymphoblastic leukemia immunophenotype: cCD3, CD7, CD34, CD33, and CD5 (dim), and negative for sCD3, CD2, CD4, CD1a, CD8, CD13, CD11b, cMPO, CD79a, CD19, CD10, CD117, and other myeloid and B-lineage antigens. The gene discussed is CD19; the disease is acute lymphoblastic leukemia.