Characteristic surface morphology of human and murine myeloma cells: a scanning and transmission electron microscopic study

Tumor necrosis factor-alpha and CD40L modulate cell surface morphology and induce aggregation in Ramos Burkitt's lymphoma cells

Interaction of CD40L and its cognate receptor is an essential component of B-lymphocyte signaling, affecting various aspects of B-cell differentiation pathways and immunoglobulin gene expression. However, much less is known about the biological consequences of B-cell signaling through tumor necrosis factor (TNF)-alpha and its cognate receptors TNF-R1 and 2. We used Ramos Burkitt's lymphoma cell line as a model system to study the direct effects of these cytokines on B cells. Treatment of Ramos cells with either TNF-alpha or CD40L, but not with interleukin (IL)- 4, interferon (IFN)-gamma and transforming growth factor (TGF)-beta, resulted in enhanced cell aggregation and enhancement of adherence to glass cover-slips. Scanning electron microscopy showed that Ramos cells have a polarized cell surface morphology and exhibit at least 3 cell surface morphological domains: microvilli, filopodia and ruffled membranes. The cells adhered to the glass matrix through multiple filopodia/podopodia-like cell processes and demonstrated distinct ruffled-like membrane projections on their opposite pole. Induction by TNF-alpha or CD40L, but not with IL-4, IFN-gamma and TGF-beta, resulted in increased number and complexity of both types of membrane projections. TNF-alpha and CD40L upregulated the expression of the adhesion molecule intercellular adhesion molecule-1 and the Fas receptor on Ramos cells, without affecting the expression levels of membrane immunoglobulin M or its secretion rate. Reverse transcriptase-polymerase chain reaction, and flow cytometry demonstrated that Ramos cells expressed TNF-R1 but very little if any TNF-R2, indicating that TNF-alpha exerted its effects on Ramos cells through the former receptor.

Immunoglobulin synthesis in the human myeloma cell line U-266; expression of two immunoglobulin heavy chain isotypes (epsilon and alpha) after long-term cultivation in vitro

A human IgE-producing myeloma has been cultivated in vitro as a continuous cell line (U-266) since 1968. Analysis of immunoglobulin production during early passages of the cell line demonstrated a high synthesis rate of monoclonal IgE. Analysis of late passages, cultivated after 1980, revealed a 3-6-fold lower rate of IgE secretion. This decrease was accompanied by the appearance of small amounts of IgA in the culture medium together with IgE. RNA was extracted from a late passage of U-266 and analyzed by Northern blotting, using epsilon and alpha-specific oligonucleotides as hybridization probes. The results showed the presence of epsilon as well as alpha-specific mRNA. Moreover the results demonstrated that the latter mRNA was derived from the alpha 2 locus and that the epsilon and the alpha 2-specific mRNA contained the same V region sequences. Southern blot analysis of DNA from the late passage of the U-266 cell line failed to reveal a recombinatory switch from the epsilon locus to the alpha 2 locus. The expression of alpha 2 is thus likely to be caused by differential splicing rather than by an isotype switch at the DNA level.

Ultrastructural studies of myeloma cells: observations concerning the Golgi apparatus and intermediate-size filaments

Studies on the ultrastructure of tumor cells of 22 multiple myeloma patients revealed hitherto unreported observations concerning the Golgi apparatus and intermediate-size filaments. Various abnormalities of the Golgi apparatus including displacements of the Golgi stacks, dilatations of cisternae, and massive accumulations of vesicles as well as vacuoles in the Golgi region were found in myeloma cells of 11 patients. Intermediate-size filaments forming a fine intracytoplasmic network were apparent in myeloma cells of all 22 patients. In five patients, in addition to this architecture, intermediate-size filaments were gathered into thick bundles which were primarily but not exclusively located in the perinuclear region.

Phorbol 12,13-dibutyrate (P(Bu)2)-treated human blood mononuclear cells bind to each other

Treatment of human blood mononuclear cells with nanomolar concentrations of phorbol 12,13-dibutyrate (P(Bu)2) induced their aggregation. The phenomenon was seen within a few minutes and reached its maximum manifestation after 20 min. At this time, 20-30% of unfractionated and nylon wool-passed mononuclear leukocytes were in the aggregates. The influence of pretreatment with 2-deoxyglucose, NaN3, EDTA, cyclohexamide, or incubation at 4 degrees C on the phenomenon indicated that it is energy and temperature dependent, requires the presence of extracellular divalent cations, and is independent of protein synthesis. Nonaggregating 2-deoxyglucose-and NaN3-pretreated cells could still bind [3H]P(Bu)2 which rules out the possibility that the phorbol ester molecule acts as a bridge between the aggregated cells. Seventeen percent of the P(Bu)2-treated T-cell population bound untreated autologous and allogeneic cells. The binding property has a certain species specificity because only 4% of the cells interacted with mouse lymphocytes. At the ultrastructural level, the intercellular binding showed broad areas of surface contact (both between lymphocytes and lymphocyte-monocyte) and "trapping" by surface processes was not seen. Aggregated cells did not show cytopathogenic changes.

The contribution of scanning electron microscopy in haematology: its role in defining leucocyte and erythrocyte disorders

This report reviews the contribution of scanning electron microscopy (SEM) in haematology. Important observations regarding red cell shape and deformities are referred to and contributions in the definition and classification erythrocyte disorders are stressed. In this field there is no doubt that SEM has contributed much to the three-dimensional visualization of RBC disorders. As far as leucocyte pathology is concerned the situation is less clear. SEM has contributed much to current knowledge and understanding of the surface properties of white blood cells. Normal leucocytes have different surface features and can be distinguished under the SEM. However, some overlap does occur, making individual distinction on the basis of surface architecture alone extremely difficult. The difficulties in this regard are discussed in this review and factors influencing the variability of surface microprojections are reviewed briefly. Leukaemic cells of different origins may also be distinguished under the SEM. However, while "hairy' cells have typical surface features and non-lymphoid leukaemic cells, in particular monocytes, are readily distinguished from lymphoid leukaemic cells, there is much overlap of surface topography. Undifferentiated cells and early myeloblasts and lymphoblasts have similar surface features and cannot be distinguished under the SEM. While SEM adds a valuable third dimension to morphology and ultrastructure, it cannot be used alone in the definition of difficult cases of acute leukaemia.

Suppressive effect of ferritin on in vitro lymphocyte function

This study describes the effect of ferritin on lymphocyte function in vitro. Peripheral blood lymphocytes isolated from normal donors were incubated with purified human splenic ferritin, and the mitogenic effect of phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM) and mixed lymphocyte reaction (MLR) were assessed by the uptake of 3H-thymidine (3H-TdR). Ferritin (0.25--5.0 micrograms/ml culture) caused a marked suppression of PHA nad Con A blastogenesis but had no suppressive effect on PWM-induced transformation. Maximal suppression was obtained at a ferritin concentration of 1 microgram/ml and this was not enhanced by increasing ferritin concentrations. Ferritin also reduced the Con A capping phenomenon in normal lymphocytes from 22% to 6%, suppressed the MLR reaction but had no effect on the ability of normal lymphocytes to form E, EA and EAC rosettes or on in vitro lymphocyte cytoxicity against the K-562 cell line. Visual proof of the suppressive effect of ferritin on mitogen induced blastogenesis was provided by scanning electron microscopy, and direct evidence for the ability of lymphocytes to bind ferritin was obtained from studies with radioiodine labelled ferritin. The above findings indicate that ferritin suppresses certain parameters of T-lymphocyte function in vitro. The relation of the present findings to recognized abnormalities of T-cell function encountered in certain neoplastic disorders associated with high serum ferritin levels is at present unknown.