Nucleoside phosphorylase activity in normal and leukemic cells

T-cell acute lymphoblastic leukemia in Israel: clinical and laboratory features

T-cell acute lymphoblastic leukemia (ALL) comprises a third of the cases of childhood ALL in Israel. This high proportion of T-ALL is most probably due to a deficiency in pre-B/common ALL. The T-ALL patients had significantly worse 4-yr survival compared to standard risk or non-T high risk patients. In view of these special epidemiologic and clinical features a study of the immunophenotype of all consecutive cases of T-ALL and T-non Hodgkin's lymphoma (NHL) observed in our medical center was performed. Twenty-eight ALL and 3 NHL patients were studied and their cells characterized using a panel of monoclonal antibodies, TdT reactivity and E-rosette formation. Assays of the activities of adenosine deaminase (ADA) and purine nucleoside phosphorylase (NP) were also performed. Based on the surface antigen expression, the tumor cells could be classified into one of the three known developmental stages of T cells. It was found that the immunophenotype of the T-ALL cases in Israel was similar to that observed in other countries. Considerable heterogeneity of surface antigen expression was found and in a number of cases the phenotype analysis was not easily reconciled with models of T-cell ontogeny. The activities of ADA and NP were correlated with the developmental stage, as defined by the surface antigenic expression. Contrary to observations on normal T-cells, where ADA activity decreases and NP activity increases as T-cells mature and differentiate, this was not found in the malignant T cells. These findings as well as the existence of atypical immunophenotypes suggest that the leukemic T cell has an abnormal gene expression.

Enzyme alterations in leukemic cells

Recently, much attention has been focused on various enzyme alterations found in leukemic cells. Most of the data generated thus far has involved the study of terminal deoxynucleotidyl transferase, the purine pathway enzymes, and hexosaminidase and other lysosomal enzymes. Differences in both total enzyme activities and isoenzyme patterns have been found to occur among the various leukemia types and subtypes. These changes may prove to be useful aids in diagnosing, classifying, detecting subclinical recurrent or residual disease, and as therapeutic determinants in hematopoietic neoplasia, especially in the lymphoid malignancies.

Acute lymphoblastic leukemia subtypes in Israel: the Sheba medical center experience

During the period from 1978 to 1981, 52 patients with ALL were diagnosed and treated at the Chaim Sheba Medical Center. Using standard cell markers to subtype the blasts, 49 of the patients could be classified: 16 were found to be T-cell ALL, 10 common ALL, five null ALL, four pre-B and 14 were partially characterized as non-B, non-T. Analysis of the series revealed two distinctive features: high prevalence (30%) of T-cell ALL among both Jews and Arabs and a high proportion, two-thirds, of high risk patients due to high initial WBC counts, unfavourable age or T-cell characteristics. The minimal incidence of ALL among the Gaza Strip Arab children during the study period is 4:100,000, which is close to the incidence in the Western world. During previous years the leukemia incidence in the Gaza Strip was very low while the most common lymphatic malignancies were Burkitt tumor and other non-Hodgkin lymphomas.