Independent expression of the surface markers 5'-nucleotidase and cALLA on leukemic cells

High levels of the ectozyme 5'-nucleotidase (5'-N) and the common ALL-antigen (cALLA) are coexpressed on leukemic blast cells in common ALL, in the lymphoid blast crisis of CML and also on the lymphoblastoid cell-line Nalm-1. Clinically this coexpression can help to subclassify leukemias and may be of diagnostic and prognostic significance. In an attempt to study the mechanism underlying this simultaneous expression plasmamembrane subfractionation was undertaken on Nalm-1. When membrane-shedding from intact cells is induced by sublytic concentrations of the lysophosphatidyl-choline analogue ET-12-H, membrane subfractions are obtained which contain 30-40% of total cellular 5'-N, which is most of the enzyme carried on the cell surface, in a highly enriched form. Under these conditions only a very low release of intracellular enzymes is observed. On the other hand cALLA is not accumulated in these membrane fractions to any appreciable extent. The predominant part of this antigen is still on the intact cells remaining after the shedding procedure. It is concluded that the simultaneous expression of 5'-N and cALLA on Nalm-1 and leukemic blasts is not regulated by a physical association or a close neighborhood of these antigens on the membrane level.     

Extinction of B-cell surface differentiation markers in hybrids between murine B-lymphoma and myeloma cells

Fusion between murine B-lymphoma cells bearing membrane IgM with either IgG or light chain secreting myeloma, resulted in cell hybrids synthesizing and secreting large quantities of IgM. In contrast, the hybrids did not secrete IgD even though it is also present on the surface of the B-lymphoma cells. B-Cell surface markers such as the IgM, IgD, Ia and the Fc receptor, which were present on the B-lymphoma cells, but not the myeloma cells were not expressed on the surface of the hybrids. Hybrids which secrete IgM and retain the B-cell membrane differentiation antigens were not detected, even when selection was done under conditions which favor the growth of the lymphoma parental cells.     

4-Hydroxynonenal, an end-product of lipid peroxidation, induces apoptosis in human leukemic T- and B-cell lines

4-Hydroxynonenal (HNE) is the major aldehydic product resulting from lipid peroxidation and has been implicated as involved in several pathological conditions. In our continuing studies on the role of membranes and lipid peroxidation in the induction of apoptosis, we investigated the effect of HNE on cultured human malignant immune system cells. Two cell lines were utilized; MOLT-4, a human T-cell leukemia cell line, and Reh, a human B-cell lymphoma cell line. A 10 min treatment with 0.01 mM HNE resulted in the apoptotic death, as determined by flow cytometric and morphological analyses, of both cell lines within 24 h. MOLT-4 cells exhibited the manifestations of impending apoptotic death much sooner than did Reh cells, indicating that MOLT-4 cells were more sensitive or not as efficient at detoxifying HNE than were Reh cells. These results suggest that peroxidative damage to cellular membranes resulting in the production of HNE may be a trigger for the induction of apoptosis in immune system cells.     

4-Hydroxynonenal,an end-product of lipid peroxidation,induces apoptosis in human leukemic T- and B-cell lines

4-Hydroxynonenal (HNE) is the major aldehydic product resulting from lipid peroxidation and has been implicated as involved in several pathological conditions. In our continuing studies on the role of membranes and lipid peroxidation in the induction of apoptosis, we investigated the effect of HNE on cultured human malignant immune system cells. Two cell lines were utilized; MOLT-4, a human T-cell leukemia cell line, and Reh, a human B-cell lymphoma cell line. A 10 min treatment with 0.01 mM HNE resulted in the apoptotic death, as determined by flow cytometric and morphological analyses, of both cell lines within 24 h. MOLT-4 cells exhibited the manifestations of impending apoptotic death much sooner than did Reh cells, indicating that MOLT-4 cells were more sensitive or not as efficient at detoxifying HNE than were Reh cells. These results suggest that peroxidative damage to cellular membranes resulting in the production of HNE may be a trigger for the induction of apoptosis in immune system cells.     

Stimulation of chicken lymphocytes by T- and B-cell mitogens.

Cultures of chicken spleen, peripheral blood, thymus, and bursal lymphocytes were tested for mitogenic stimulation by phytohaemagglutinin (PHA), concanavalin A (ConA), pokeweed mitogen (PWM), bacterial lipopolysaccharide (LPS), trypsin, and insulin. Spleen and blood leukocytes were stimulated by both the lectins and LPS, and also to some degree by trypsin and insulin as judged by increased incorporation of [³H]thymidine into acid-insoluble material. This was observed in cultures incubated in serum-free medium as well as in the presence of foetal bovine serum or autologous plasma. Thymus cells were reproducibly stimulated by high concentrations of PHA. No significant responses were obtained in bursal cell cultures with any of the compounds tested. Removal of cotton wool-adherent cells from the spleen cell suspensions resulted in a subpopulation of cells which were stimulated by PHA but showed little response to ConA, PWM, or LPS. This procedure did not remove surface immunoglobulin-bearing cells from the original suspension. Both these enriched spleen lymphocytes and the unfractionated spleen, blood and thymus leukocyte cultures were effectively stimulated by a partially purified PHA but with a highly purified PHA preparation only at very high concentrations. These and other results suggest that the mitogenic components in crude PHA preparations are different for chicken and human or mouse cells.     

B-cell lymphoma 6 promotes proliferation and survival of trophoblastic cells

Preeclampsia is one of the leading causes of maternal and perinatal mortality and morbidity and its pathogenesis is not fully understood. B-cell lymphoma 6 (BCL6), a key regulator of B-lymphocyte development, is altered in preeclamptic placentas. We show here that BCL6 is present in all 3 studied trophoblast cell lines and it is predominantly expressed in trophoblastic HTR-8/SVneo cells derived from a 1^st trimester placenta, suggestive of its involvement in trophoblast expansion in the early stage of placental development. BCL6 is strongly stabilized upon stress stimulation. Inhibition of BCL6, by administrating either small interfering RNA or a specific small molecule inhibitor 79–6, reduces proliferation and induces apoptosis in trophoblastic cells. Intriguingly, depletion of BCL6 in HTR-8/SVneo cells results in a mitotic arrest associated with mitotic defects in centrosome integrity, indicative of its involvement in mitotic progression. Thus, like in haematopoietic cells and breast cancer cells, BCL6 promotes proliferation and facilitates survival of trophoblasts under stress situation. Further studies are required to decipher its molecular roles in differentiation, migration and the fusion process of trophoblasts. Whether increased BCL6 observed in preeclamptic placentas is one of the causes or the consequences of preeclampsia warrants further investigations in vivo and in vitro.     

Studies on cell surface conformation following injury. II. Scanning and transmission electron microscopy of cell surface changes following anoxic injury in Ehrlich ascites tumor cells.

Exposure of Ehrlich ascites tumor cells to anoxia resulted in rapid and characteristic conformational changes of cell surface topography. Combined scanning and transmission E/M studies revealed rapid alterations including simplification of the cell surface configuration with disappearance of microvilli which were replaced with formation of blebs and recesses at the cell periphery. These surface changes were accompanied by characteristic organelle alterations inside the cells which in this and other cellular systems have been shown to be reversible. Later, the cell surface topography became smoother and monotonic with small blebs and cribriform invaginations in addition to larger eruptions of the cell periphery. Combined transmission E/M studies revealed fragmentation of cellular membrane systems and lysis of organelles indicating the irreversible phase of anoxic injury. The rapid conformational surface changes encountered in Ehrlich ascites tumor cells following anoxia suggest the important role of the plasma membrane and its unfolding as a virtually instantaneous response of the cells to this injury.     

Phosphorylation of myosin light chain during capping of mouse T- lymphoma cells

Colchicine induces the clustering of at least three different T- lymphoma surface antigens (T200, Thy-1, and gp 69/71) into a cap structure in the absence of any external ligand. In addition, colchicine induces the intracellular accumulation of actin and myosin directly beneath the surface cap structure. We have discovered that myosin molecules (both heavy and light chains) are closely associated with the plasma membrane of T-lymphoma cells. Most importantly, we have found that the 20,000-dalton light chain of lymphocyte myosin is both phosphorylated and preferentially accumulated in the plasma membrane of colchicine-induced capped cells. It is proposed that myosin light chain is directly involved in the activation of membrane-associated actomyosin required for the collection of surface proteins into a cap structure (analogous to muscle cell sliding filament contraction).     

Expression of immunological markers on leukemic cells before and after cryopreservation and thawing

We have studied the effects of cryopreservation on the viability and on the expression of surface antigens of acute leukemia cells. Marrow samples were obtained at initial diagnosis from 89 patients with acute myeloid leukemia (AML), acute undifferentiated leukemia (AUL), and acute lymphoid leukemia (ALL). In AML, the mean viability was greater than 90% in the types M1, M4, and M5 of the French-American-British classification, 79% in M2, and 3% in M3 types. The viability was 74% in AUL. In ALL, the viability was 95% for pre-B leukemias, but only 2% in T-cell leukemias. The expression of myeloid antigens was studied before and after freezing and thawing using three monoclonal antibodies (NHL30.5, against poorly differentiated granulocytic leukemias, VIMC6 against differentiated granulocytic leukemias and granulocytes; and UCHM1 or CRIS-6, against monocytic leukemias and monocytes). The percentage of cells stained by NHL30.5 and UCHM1 or CRIS-6 was very similar before and after cryopreservation. For VIMC6, the mean staining after cryopreservation was 60% of the initial one. In pre-B ALL, the stainings by anti common ALL antigen before and after cryopreservation were also very similar. We conclude that leukemic cryopreserved cells are suitable for immunologic studies. The recovery is, however, very low in promyelocytic AML and T-cell ALL.     

Automatic alignment of transmission electron microscope tilt series without fiducial markers

Accurate image alignment is needed for computing three-dimensional reconstructions from transmission electron microscope tilt series. So far, the best results have been obtained by using colloidal gold beads as fiducial markers. If their use has not been possible for some reason, the only option has been the automatic cross-correlation-based registration methods. However, the latter methods are inaccurate and, as we will show, inappropriate for the whole problem. Conversely, we propose a novel method that uses the actual 3D motion model but works without any fiducial markers in the images. The method is based on matching and tracking some interest points of the intensity surface by first solving the underlying geometrical constraint of consecutive images in the tilt series. The results show that our method is near the gold marker alignment in the level of accuracy and hence opens the way for new opportunities in the analysis of electron tomography reconstructions, especially when markers cannot be used.     

Phenotyping human leukemic T-Cell lines: Enzyme markers; surface antigens,and cytogenetics

We have compared phenotypic markers for a series of established human leukemic T-cell lines collected from different laboratories. Cell lines were tested first for genetic markers using polymorphic enzymes and then for expression of T lymphoid cell surface differentiation antigens using monoclonal antibodies. Chromosomal analysis was used as an additional method for identification of selected cell lines. On the basis of enzyme markers, it was possible to assign each of the cell lines examined to one of nine different groups. With two exceptions, surface antigen phenotypes for each of 12 cell lines were clearly distinctive. Thus, some groups of cell lines indistinguishable by enzyme markers could be further subdivided by surface antigen phenotyping. However, significant quantitative variation in expression of individual antigens was observed. In addition, surface antigen expression was not uniform in different subcultures of one cell line studied in detail. These results indicate that leukemic T-cell lines cannot be used generally as simple models of surface antigen expression in normal T-cell differentiation.     

B-cell lymphoma lacking Fc- and C3d-receptors.

Various cell surface markers were studied in a patient with lymphosarcoma cell leukemia. The B-cell derived feature of the neoplastic cells could be identified by demonstration of monoclonal surface immunoglobulin of IgM-kappa type of high density synthesized by the cells. Interestingly, there were no Fc- nor C3d-receptors demonstrable using various techniques. Only 22% of the leukemic cells expressed C3b receptors. The failure of rosette formation with mouse erythrocytes was an additional surface feature distinguishing from ordinary chronic lymphatic leukemia of the B cell type. The phenotype of the leukemia cells is discussed as corresponding to that of a less differentiated B lymphocyte.     

Structural features of nucleoli in blood,leukemic, lymphoma and myeloma cells

At present, it seems clear that the nucleolus is multifunctional and represents one of the key cell organelles that participate directly or indirectly in cell resting, proliferation, differentiation and maturation states, and possibly also in programmed cell death. Thus, the morphology and cytochemistry of nucleoli may represent a very useful tool not only for the evaluation of nucleolar biosynthetic activities but also for the evaluation of various cell states under physiological, experimental and pathological conditions.