Terminal deoxynucleotidyl-transferase levels and membrane phenotypes in diagnosis of acute leukaemia.

Terminal deoxynucleotidyl transferase (T.D.T.) has been measured in the cells of 112 leukaemia patients whose cells were characterised by membrane markers as well as by standard haematological and cytochemical criteria. The concentration of enzyme ranged from 0.1 to 1.4 units/10(8) cells in the bone-marrows of 20 patients with normal marrow or benign marrow hyperplasia. The enzyme level was raised in 30 of 31 patients with untreated acute lymphoblastic leukaemia (A.L.L.) whose cells reacted positively with an anti-A.L.L. serum (range 0.9-197, mean 59, units/10(8) cells) and in all 9 patients with thymic A.L.L. (Thy-A.L.L.) (range 1.5-95, mean 36, units/10(8) cells). All but 1 of 17 patients with acute myeloblastic leukaemia gave negative results (range 0-1.5, mean 0.60, units/10(8) cells), and T.D.T. was also normal in all 7 bone-marrow samples from patients with chronic granulocytic leukaemia (C.G.L.) in the chronic phase. The T.D.T. assay gave a clear distinction between 11 patients with C.G.L. in lymphoid transformation, anti-A.L.L.-serum positive (range 15-226, mean 83, units/10(8) cells), and 12 patients with C.G.L. in myeloblastic transformation, anti-A.L.L.-serum negative (range 0-1.9, mean 0.7, units/10(8) cells). Among 17 patients with otherwise unclassifiable acute leukaemia, 10 gave raised values (range 1.6-113 units/10(8) cells) and 7 gave normal values. It is concluded that the assay of T.D.T. in the peripheral blood or bone-marrow of patients with acute leukaemia is of value in differentiating lymphoid (including non-T non-B and Thy-A.L.L.) from myeloid leukaemia.