Terminal deoxynucleotidyl transferase as a biological marker for human leukemia.

High levels of terminal deoxynucleotidyl transferase have been observed in leukocytes of 7 out of 20 patients with chronic myelogenous leukemia in acute blast phase of the disease. These levels are comparable to the levels observed in human and calf thymus gland and cell lines with some T cell characteristics (Molt 4 and 8402). Negligible levels of this activity were observed in chronic myelogenous leukemia not in an acute blast phase of the disease, chronic lymphocytic leukemia, human B cells, mature T cells, and the mixed population of lymphocytes present in normal human blood. The detection of this enzyme in some patients with chronic myelogenous leukemia in acute blast phase of the disease suggests that the blast proliferation may involve primitive stem cells which have more lymphoid than myelogenous characteristics. This enzyme assay may be of use as a biological marker for following patients during treatment and in remission.