Frederick J. Bollum

Identification of subsets of proliferating low Thy 1 cells in thymus cortex and medulla.

Abstract Subsets of proliferating thymocytes were identified in the normal mouse thymus by in vivo labeling with [3H]TdR and by cell separation according to relative amounts of Thy 1 antigen. In order to resolve apparent discrepancies in the literature, parenteral and topical application of [3H]TdR were compared as labeling methods for dividing thymocytes, and limited complement lysis and fluorescence-activated cell sorting were compared as separation principles for high Thy 1 and low Thy 1 thymocyte subsets. The separated cells were further characterized by immunofluorescence for terminal deoxynucleotidyltransferase (TdT), which normally is restricted to cortical thymocytes, and for H2 alloantigens, which are preponderant on medullary thymocytes. Four subsets of proliferating cortical thymocytes were identified after application of [3H]TdR to the thymus capsule. The major subset, which comprised about 92% of dividing cortical thymocytes, had a high Thy 1, low H2 phenotype. Most were also TdT + ve. The three minor subsets of proliferating cortical thymocytes each had a low Thy 1 phenotype, but differed according to H2 and TdT markers. Systemic injection of [3H]TdR also labeled the above subsets of dividing cortical thymocytes, but in addition it detected a subset of proliferating low Thy 1, low H2, TdT — ve cells in the thymus medulla. The latter subset comprised about one-third of the pool of proliferating low Thy 1 cells. In their aggregate the four subsets of low Thy 1 cells constituted approximately 13% of total proliferating thymocytes and 1.1% of total thymocytes. The identification of discrete subsets of proliferating low Thy 1 cells in the thymus cortex as well as in the thymus medulla is compatible with the hypotheses that all thymocytes are descended from low Thy 1 precursors and that separate precursor cell subsets exist for cortical and medullary thymocytes.

Polyadenylic acid polymerase activity in chronic myelogenous leukemia

Poly(A) polymerase activity was markedly elevated in CML in the blastic phase, moderately high in the accelerated phase and low in the chronic phase. The activity was significantly higher in the myeloid crisis than in the lymphoid crisis and elevated with increasing ratio of blasts in leukemia cases. In TPA or retinoic acid-treated leukemia cells poly(A) polymerase activity was decreased. These results suggest that poly(A) polymerase activity changes, depending on the maturation of leukemic cells and the assay of this enzyme activity may be useful for the early detection of the exacerbation of CML cases.

Terminal-Deoxynucleotidyl Transferase (TdT): Serial Observations on Patients with Leukemia

Terminal-deoxynucleotidyl transferase (TdT) bone marrow determinations were performed on 67 patients with leukemia using the indirect immunofluorescence technique. A total of 103 smears were evaluated on 32 patients with acute lymphoblastic leukemia. With some exceptions, TdT levels were elevated at onset, declined during induction except in resistant cases, decreased during remission on chemotherapy, showed slight elevation during remission off chemotherapy, and rose during relapse in those cases previously positive. The most important finding was that patients in remission may have elevated TdT levels. Those were usually less than 10%. A total of 124 bone marrow smears were evaluated on 29 patients with acute myeloid leukemia. In general, values in all categories were below 1%, with a few elevated between 1% to 10%. Six patients with chronic myelogenous leukemia in blast crisis had 13 bone marrow smears evaluated. Five were in myeloblastic crisis and had values of less than 1%; 1 was lymphoblastic which had 50% positive cells at onset. In our experience, TdT determinations are of value in lymphoblastic leukemia in diagnosis, in predicting response to therapy, and in detecting early relapse.

Sialyltransferase activity in leukemia.

Sialyltransferase activity in blasts from acute lymphoblastic leukemia (ALL) was markedly lower (1.68 +/- 1.23 pmol/mg protein) than those (6.18 +/- 2.22 pmol/mg protein) of lymphocytes from normal volunteers (t less than 0.001). On the contrary, enzyme activity was significantly increased in blasts (1.21 +/- 0.38 pmol/mg protein) from acute non-lymphoblastic leukemia, compared to the level (0.53 +/- 0.32 pmol/mg protein) of mature granulocytes (t less than 0.001). In TdT-negative CML in blast crisis, sialytransferase activity (2.11 +/- 0.88 pmol/mg protein) was significantly higher than those of mature granulocytes (t less than 0.001), whereas no significant difference in the enzyme activity was noted between the blasts from TdT-positive CML in blast crisis and from ALL. In TdT-positive ALL cases, there was an inverse relationship (r = -0.85, t less than 0.01) between sialytransferase activity and terminal deoxynucleotidyl transferase (TdT) activity of the blasts. Therefore, sialytransferase in leukocytes may be a unique enzyme in which changes in activity relate to the differentiation or malignant transformation of leukocytes.