Marrow terminal deoxynucleotidyl transferase activity in adult acute leukemia.

Terminal deoxynucleotidyl transferase (TdT), a unique DNA polymerase that does not require a template, is found in thymocytes and marrow Tlymphocytes normally [1,2]. Shortly after these discoveries, McCaffrey et al. [3] described the presence of this enzyme in the leukemic cells of patients with acute lymphoblastic leukemia (ALL) and Sarin et al. [4] discovered that some patients with chronic myelocytic leukemia in blast crisis have TdT activity in leukemic cells. Currently, the data from a number of laboratories indicates that most patients with ALL have TdT-positive blasts and most patients with acute nonlymphocytic leukemia (ANLL) have TdTnegative blasts [5,6]. We have measured TdT in the bone marrow of 40 adult patients with acute leukemia prior to any therapy, 30 with ANLL and 10 with ALL by the method of Sarin and Gallo [4] as previously described. One unit of TdT activity equals one (n) 3HdGMP incorporation/hr/ 109 marrow cells. In this report. TdT results are correlated with the Wright's stained morphology of the bone marrow, Periodic acid-Schiff (PAS) reaction, Sudan black reaction and response to therapy.