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Activities of the ecto-enzymes 5′-nucleotidase (5′-N) and phosphatase were determined on the surface of intact cells from 15 different established lines of human B- and T-lymphoblasts. Whereas all the lines express phosphatase, 10 of the lines were negative for 5′-N. 5′-N-negative cell lines are found among B as well as T cells, and they do not carry cryptic enzyme activity. In a 5′-N-positive line activity of this enzyme is correlated with growth showing a peak during the logarithmic phase. On the other hand, inhibition of 5′-N does not change the growth curve of this line. Neuraminidase treatment of the cell surface brings about an increase in phosphatase but not in 5′-N activity. 5′-N of two B-cell lines and of human peripheral blood lymphocytes shows complete crossreactivity with an antiserum obtained against human placental 5′-N. However, the enzyme of one lymphoma line with B-cell properties (EHR-A-Ramos) does not cross-react with this serum. The results are discussed with respect to suitability of these lymphoblast lines as model systems for the study of immunodeficiencies.

When ficoll purified peripheral blood lymphocytes were treated with fluorescein conjugated lectins from lentils (LCH), castor beans (RCA) and phaseolus coccineus beans (L- and E-PHA) for 15 min and the percentages of the cap forming cells were examined, the values of leukemic lymphocytes were reduced compared to the values obtained with normal lymphocytes. The reduction was more than half in patients with acute and chronic myelogenous leukemia and immunoblastoma, it was only one quarter in patients with chronic lymphocytic leukemia, Hodgkin's disease and lymphosarcoma. The lowest number of cap forming cells was found in lymphoblasts of established lymphoblastoid cell lines. The four different lectins showed nearly the same capacity in the induction of caps. After successive binding, the different lectins showed cocapping on the lymphocyte surface.