Scanning electron microscopy of human lymphocyte-sheep erythrocyte rosettes

Dielectric properties of human leukocyte subpopulations determined by electrorotation as a cell separation criterion

The separation and purification of human blood cell subpopulations is an essential step in many biomedical applications. New dielectrophoretic fractionation methods have great potential for cell discrimination and manipulation, both for microscale diagnostic applications and for much larger scale clinical problems. To discover whether human leukocyte subpopulations might be separable by such methods, the dielectric characteristics of the four main leukocyte subpopulations, namely, B- and T-lymphocytes, monocytes, and granulocytes, were measured by electrorotation over the frequency range 1 kHz to 120 MHz. The subpopulations were derived from human peripheral blood by magnetically activated cell sorting (MACS) and sheep erythrocyte rosetting methods, and the quality of cell fractions was checked by flow cytometry. Mean specific membrane capacitance values were calculated from the electrorotation data as 10.5 (+/- 3.1), 12.6 (+/- 3.5), 15.3 (+/- 4.3), and 11.0 (+/- 3.2) mF/m2 for T- and B-lymphocytes, monocytes, and granulocytes, respectively, according to a single-shell dielectric model. In agreement with earlier findings, these values correlated with the richness of the surface morphologies of the different cell types, as revealed by scanning electron microscopy (SEM). The data reveal that dielectrophoretic cell sorters should have the ability to discriminate between, and to separate, leukocyte subpopulations under appropriate conditions.

All-trans retinoic acid induces functional maturation of epidermal Langerhans cells and protects their accessory function from ultraviolet radiation

Retinoids provide some protection against ultraviolet radiation-induced skin damage. We have previously shown that topical all-trans retinoic acid prevents ultraviolet light from reducing the density of epidermal Langerhans cells in the epidermis but does not inhibit the development of immunosuppression to a locally applied contact sensitizer. We therefore investigated the ability of all-trans retinoic acid to modulate Langerhans cell induction of allogeneic T-cell proliferation in the mixed epidermal cell lymphocyte reaction. Langerhans cells isolated from all-trans retinoic acid-treated mice induced an enhanced mixed epidermal cell lymphocyte reaction. This is similar to Langerhans cells cultured with granulocyte-macrophage colony stimulating factor. Retinoic acid treatment also enhanced the allogeneic cell-stimulating capability of Langerhans cells isolated from ultraviolet-irradiated mice. Langerhans cells from all-trans retinoic acid-treated, ultraviolet-irradiated mice which were "matured" by 3 days in culture induced a larger mixed epidermal cell lymphocyte reaction than mice treated with solvent and ultraviolet irradiation. Thus all-trans retinoic acid treatment of mice causes Langerhans cell maturation and inhibits ultraviolet light from reducing their density or impairing their allogeneic cell-stimulating capacity. However, these mice remained immunosuppressed upon application of a contact sensitizer to irradiated or unirradiated skin. It is thus likely that, whereas all-trans retinoic acid protects local Langerhans cell numbers and function, it does not inhibit the production of an ultraviolet radiation-induced photoproduct which causes immunosuppression.

Activation and enhanced contact of human T-lymphocytes with autologous red blood cells are required for their stable adherence at 37 degrees

The adherence of human red blood cells (RBC) to autologous T-cells does not occur in the body, and in vitro is elicited at 4 degrees. Autologous E-rosetting at 37 degrees has not previously been described. In this work, lymphocyte-RBC adherence has been studied in mixed leukocyte-RBC cultures and in whole blood from healthy donors. Vital, cytochemical and electron microscopic studies have shown that T-cells may form stable E-rosettes with autologous RBC at 37 degrees. As in the previously reported cold-dependent reversible rosetting, stable rosetting is mediated by the erythrocyte LFA3 and lymphocyte CD2 molecules. Uniquely, this phenomenon requires both T-cell activation and an enhanced contact between the T-cell and RBC membranes. These requirements were met by exposure of cell cultures to: (1) PHAE, the erythroagglutinating component of PHAP, or (2) to either non-erythroagglutinating mitogens, PHAL, Con A, OKT3 or SEA, or to antigens of typhus group rickettsiae or salmonellae, provided that the RBC membrane was desialyted. Cultures derived from individuals seropositive to rickettsiae or vaccinated with salmonellae demonstrated the adherence phenomenon after antigen exposure when neuraminidase was present in the culture medium. The system 2 described here can be used as a diagnostic tool for defining activated T-cells and T-cell clones with the memory to antigens capable of inducing cell-mediated immunity.

Polarization optical analysis of blood cell membranes

The present study deals with investigations of membrane structure using polarization topo-optical reactions. Polarization microscopy is a special field of biological submicroscopic morphology. It represents a powerful tool well able to reveal the features of organization of biological structures, and the regularity of macromolecules building cells and tissues - properties that cannot directly be studied by other approaches to complex biological systems. Only in "pure" systems can X-ray diffraction, or the analysis of circular dichroism and the dispersion of optical rotability provide data equivalent to those obtained by polarization microscopy in complex systems. One of the main drawbacks of molecular biology is that most information is relevant to isolated, purified particles or macromolecules. Thus, no conclusions can be drawn concerning the original arrangement of molecules. The gap between biochemical-biophysical and morphological approaches to molecular arrangement in complex structures is bridged by the polarization optical technique. As was pointed out in the introduction, polarization microscopy became a routine biological research method following the pioneering work of Romhányi. His enlightening topo-optical reactions (Romhányi 1960, 1963, 1966) were based on the oriented dye binding of the original charge carriers of regularly arranged tissue constituents. The second group of Romhányi's topo-optical reactions comprised procedures such as sulfation (Romhányi et al. 1973, 1974), the aldehyde-bisulfite-toluidine blue (ABT) reaction (Romhányi et al. 1974, 1975), the permanganate-bisulfite-toluidine blue (PBT) reaction (Fischer 1979, 1979a), and the sialic acid-specific reaction (Makovitzky 1980) all of which operate with induced dye-binding groups; i.e. dye-binding moieties on biological macromolecules are produced by specific chemical reactions.

Topo-optical reactions and polarization optical analysis of human lymphocytes

The latent birefringence of lymphocyte membranes of various species may readily be studied and analysed by various topo-optical reactions. The membranes of glutaraldehyde-fixed and PBS-washed lymphocytes show continuous birefringence with thiazine- and quinoline dyes. According to polarization optical analysis thiazine dye-stained cells are radially positive, whereas quinoline dye-stained cells are radially negative spherites, i.e. thiazine dye molecules are in a perpendicular, quinoline dye molecules in a parallel orientation relative to the membrane surface. These findings suggest that in lymphocyte membranes glycoproteins are primarily responsible for the topo-optical reactions. The actual conformational state of the glycoprotein components is a decisive factor not only in dye binding but also in the orientation of dye molecules. Heparin treatment directs attention to an important interaction between heparin and membrane glycoproteins. With the aid of the critical electrolyte concentration (CEC) technique we were able to demonstrate an ultrastructural differences between human erythrocyte and human lymphocyte membranes. After this procedure the birefringence of erythrocyte membranes was lost, whereas that of lymphocyte membranes did not change. There were no differences between the topo-optical reactions of T and B lymphocytes.

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.

Positive identification of human leukaemic cells with scanning immuno-electron microscopy, using antibody coated polystyrene (latex) beads as markers

Scanning immuno-electron microscopic labelling techniques were successfully used to identify a variety of leukaemia-lymphoma cells. Anti-T, -B and -common type acute lymphoblastic leukaemia (ALL) antisera were covalently conjugated to polystyrene latex spheres by means of glutaraldehyde. Peripheral blood mononuclear cells obtained from healthy individuals and from patients with T-type ALL, B-type chronic lymphocytic leukaemia (CLL), acute and chronic non-lymphoblastic leukaemias (ANLL) and cultured leukaemia-lymphoma cells were incubated with the above antisera-latex conjugates. Positively labelled cells were easily identified by the presence of latex spheres on their surfaces. Cross reactivity of the antisera used and non-specific attachment of the markers were infrequently encountered. The results of this study confirm earlier scanning electron microscopic reports indicating that different leukaemic cells have characteristic surface features and show that scanning immuno-electron microscopy (SIEM) can readily be applied to the study of human leukaemic cells.

Separation of functional subpopulations of murine and human lymphoid cells on colloidal silica density gradients. I. Preparation of the Ludox AM gradient material and characterization of separation capacities

This report describes a unique modification of an isopycnic density gradient system utilizing as a separating menstrum colloidal silica (Ludox AM). The primary advantages of this preparation are: (1) It is chemically defined, allowing extremely reproducible cell separation employing different lots of material; (2) the physical parameters (pH, density, salt concentration) of the final gradient suspension can be manipulated over a wide range of values, allowing for the separation of many different biological materials; (3) it allows separation of very large numbers of lymphoid cells with greater than 95% recovery of applied cells; (4) separated cellular subpopulations can be easily washed free of silica and cellular function is retained. This paper is a report of the preparation and functional characteristics of the gradient material as it relates to the separation of very large numbers of lymphoid cell subpopulations in both mouse and man. Subpopulations of murine and human lymphocytes separated by this gradient material were assayed for IgM synthesis, T-cell mediated cytotoxicity, and lymphokine production.

The pattern of lymphocytes in the thymus and spleen after labeling with 3H-thymidine and 3H-deoxycytidine

Adult male untreated mice (NMRI) were investigated after radioactive labeling with 3H-thymidine and 3H-deoxycytidine to find out whether the lymphocytes in the cortex and medulla of the thymus as well as in the perifollicular and periarteriolar regions of the spleen show a labeling pattern which allows a classification into T- and B-lymphocytes. The percentages of radioactively labeled small lymphocytes and their mean grain counts were determined. The percentages of radioactively labeled small lymphocytes after 3H-TdR and 3H-CdR showed no significant differences in both splenic zones. The grain counts over the lymphocyte nuclei in the periarteriolar zone showed lower values after 3H-TdR than after 3H-CdR. The lymphocytes in the perifollicular zone were strongly labeled with 3H-TdR and weakly labeled with 3H-CdR. In the thymus medulla, lymphocytes were weakly labeled with 3H-thymidine and strongly labeled with 3H-CdR. In the cortex no significant differences were observed. 75 to 80% of the small lymphocytes in the peripheral blood were weakly and 20-25% strongly labeled after 3H-TdR. Therefore there are similarities in the radioactive labeling pattern of thymic medulla lymphocytes and that of small lymphocytes of the periarteriolar zone of the spleen by both DNA precursors. The small lymphocytes in the peripheral T-dependent tissue zones, for example in the spleen, as well as in the mixed lymphocyte population of the peripheral blood can be differentiated from the B-lymphocytes through the difference in the amount of incorporation of 3H-thymidine and 3H-deoxycytidine.

Murine macrophage-lymphocyte interactions: scanning electron microscopic study

Light and scanning electron microscopic observations revealed murine macrophage-lymphocyte interactions involving the initial contact of peritoneal, spleen, or thymus lymphocytes with peritoneal macrophage processes or microprocesses followed by clustering of lymphocytes over the central nuclear area of the macrophages. Lymphocyte-lymphocyte clustering was not observed in the absence of macrophages. Attachment and subsequent clustering appeared not to require the presence of serum or antigen; the attachment of allogeneic or xenogeneic lymphocytes was comparable to that seen in the syngeneic system, but central clustering of these lymphocytes failed to occur. No attachment or clustering was observed when thymic lymphocytes were cultured with thymus derived fibroblasts rather than with peritoneal macrophages. Lymphocyte attachment to immune, antigen-activated, syngeneic macrophages occurred more rapidly than that to normal unstimulated syngeneic macrophages; however, lymphocytes attached to the "activated" macrophages appeared to be killed by a nonphagocytic mechanism. A similar increase in the rate of lymphocyte attachment to macrophages occurred in the presence of migration inhibitory factor. Subsequent lymphocyte clustering on macrophages was observed in the migration inhibitory factor-stimulated cultures. In addition, lymphocyte-macrophage interactions similar to those in vitro were observed to occur in vivo on intraperitoneally implanted cover slips.

Scanning electron microscopy of lymphoid cells from leukemia virus-infected mice

Spleen, lymph node, bone marrow, and thymus cells from Friend leukemia virus (FLV)-infected mice were examined by scanning electron microscopy. Whereas splenocytes from normal, noninfected animals showed the expected morphological classes of lymphocytes, including cells with numerous villous projections and smoother cell types, spleen cells from mice infected with FLV showed a rapid alteration of surface morphology. Shortly after infection, a decrease in the number and percentage of villous cells occurred, with a concomitant increase in the number of cells that were larger and smoother. Within 10 to 20 days after infection, the majority of splenocytes were smooth, large cells showing many distinct morphological charges, including surface "holes" and a "spongy" appearance. By days 25 to 35 after infection, most splenocytes were abnormal in appearance. Similar changes occurred in the lymph nodes after FLV infection, but the rate of change was much lower. Abnormal and larger smooth-surfaced cells did not become prominent until after week 2 or 3 infection. Thymus and bone marrow cells showed little if any change in surface morphology until late in the infectious process. However, even at that time only a few of the cells were abnormal in appearance. The changes in cell population in the spleen but not the lymph nodes paralleled the rapid decrease in the percentage of cells which stained positive for surface immunoglobulin and theta antigen. Futhermore, FLV antigen rapidly appeared on spleen cells after infection; fewer lymph node cells were positive, and only low numbers of marrow and thymus cells stained positive for FLV antigen. The marked immunosuppression induced by FLV infection paralleled and in some instances preceded the marked morphological changes.

Scanning electron microscopy and the surface morphology of human lymphocytes

The surface of the human lymphocyte as seen by the scanning electron microscope shows variations which may reflect the functional state or environment of the cell. Preparative techniques and future developments in this area are reviewed.

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

Cells from cultured human and murine myeloma cell lines and circulating leukaemic plasma cells from four patients with generalized myeloma were studied by transmission and scanning electron microscopy and time-lapse cinematography. Both circulating and cultured cells exhibited consistent surface architectures and varying numbers of prominent blebs of different sizes were seen, in addition to microvilli. The presence of surface blebs appears to be a characteristic feature for secreting and non-secreting myeloma cells.

Surface immunoglobulin of human lymphocytes

Using ferritin as surface marker, the localization of the surface immunoglobulin (Ig) was studied on peripheral lymphocytes from normal human individuals and patients with macroglobulinaemia Waldenström by scanning immunoelectron microscopy. Normal IgG-, IgM-lymphocytes and pathological IgM-lymphocytes were then compared with regard to their topographical differences. In all cells examined, IgG- and IgM-conjugated ferritin particles were detected all over the cell surface, but the distribution of the former on the normal IgG-lymphocytes was slightly more diffuse than that of the latter on the normal and pathological IgM-lymphocytes. Furthermore, in the pathological IgM-lymphocytes, the clustered IgM-conjugated ferritin particles were found in great number on the microvilli. Normal IgG-lymphocytes were almost always characterized by short rod-like microvilli standing densely and vertically on the cell surface. Some of normal IgM-lymphocytes had a similar appearance to those of normal IgG-lymphocytes (type A) but others (type B) had tilted rod-like microvilli or wide plate-like processes on their surface. As for IgM-lymphocytes of macroglobulinaemia, most lymphocytes had tilted rodlike mirovilli and wide plate-like processes similar to type B, whereas a minor population of the pathological lymphocytes carried long, thin rod-like microvilli standing vertically on the surface.

Ultrastructural studies of leucocytes which form rosettes with homologous erythrocytes in human auto immune haemolytic anaemia

Leucocytes which form rosettes with himologous erythrocytes in auto-immune haemolytic anaemia, infectious mononucleosis and following the stimulation of lymphocyte cultures with PHA have been studied by electron microscopy. The studies showed that the predominant homologous rosette forming cell was lymphocytic and the evidence favoured the conclusion that they were non-immune in nature. This identification does not classify the lymphocyte as thymus or bone marrow derived. Just under half (44%) of the total lymphocytic RFC had perinuclear microfilaments and limited clearing of the plasma of ribosomes close to the cell membrane. These features are consistent with activated T lymphocytes. The remainder of the lymphocytic RFC had no features which allowed their identification as T or B cells. The form of contact between lymphocytic RFC and erythrocyte was mainly of a pointlike nature, with little deformation or invasion of the attached erythrocytes. Monocytes were the only other type of cell encountered with any frequency. Their prime distinguishing feature was the deformation of attached red cells which they caused.

Semiquantitative determination of Cc and C3 receptors on human lymphocytes by isotope-labelled marker cells

The number of Fc and C3 receptors on normal B lymphocytes, isolated from blood, was assessed semiquantitatively by a new method in which the marker cells (pretreated sheep erythrocytes) for Fc and C3 receptors are labelled by 99Tc and 51Cr respectively. The mean number of bound marker cells per rosette was assessed simultaneously by measurements of radioactivity. Control studies showed that a measuring system using 1/4 agglutinating titre of antibody on the marker cells is particularly advantageous: (1) Fc and C3 receptors are not demonstrable on T lymphocytes; thus, B lymphocyte fractions with Fc and/or C3 receptors are well-defined. (2) The binding affinity of the marker cells for normal lymphocytes is so weak that the number of bound marker cells per rosette rarely reaches the maximum which was calculated and measured as about 30 marker cells per rosette; thus, the measuring system is sensitive to changes in the number of receptors. (3) By binding of marker cells to lymphocytes bearing Fc as well as C3 receptors it has been demonstrated that interference phenomena between the two marker cells are not operative. Studies of blood lymphocytes from normal human subjects showed B lymphocytes carrying either Fc and C3 receptors as well as a fraction of B lymphocytes having both Fc and C3 receptors. The latter maker up about 6% of the lymphocyte mass. Comparative assessment of the quantitative distribution of these receptors indicates a developmental sequence, B lymphocyte with Fc receptors evidently developing, via B lymphocytes with Fc as well as C3 receptors, into B lymphocytes having C3 receptors only.

Morphological differences between sub-populations of human lymphocytes revealed by scanning electron microscopy

Human lymphoid cells were examined by scanning electron microscopy (SEM) to see if a correlation existed between surface morphologic features and the presence of various surface markers and receptors. When viewed by SEM thymocytes appeared as smooth-surfaced cells with few surface microvilli; peripheral blood lymphocytes (PBL) on the other hand were moderately to densely villate with no entirely smooth-surfaced cells observed. Surface morphology within PBL samples was not uniform, due mainly to variations in the shape and number of microvilli. However, 2 distinctive types of surface morphology (termed Types 1 and 2) were discernable with a small number of cells displaying features of both groups (Type 3). The majority of E-rosette forming cells (T lymphocytes) displayed Type 1 and the majority of cells bearing demonstrable surface immunoglobulin (B lymphocytes) displayed Type 2 morphology. Exposure of PBL to anti-T cell specific ALG resulted in cytolysis of cells with Type 1 morphology while cells with Type 2 morphology appeared largely unaffected. PBL with Fc and C3 receptors displayed all 3 types of morphology. It is concluded that T and B lymphocytes do have subtle but nevertheless discernable differences in surface morphology and within these 2 groups, variations in surface morphology are probably associated with changes in the physiological status of the cell.

The effects of preparative procedures for scanning electron microscopy on the size of isolated lymphocytes

The diameter of lymphocytes, isolated from a sample of peripheral blood by Ficoll-Hypaque sedimentation, was determined after eight different steps in the preparative procedure for scanning electron microscopy (SEM). There was a 43% total reduction in mean cellular diameter of the lymphocytes studied, the diameter dropping from 8.4 mum prior to fixation, to a final diameter of 4.8 mum in the cells examined under the scanning electron microscope. The bulk of this shrinkage occurred during critical-point drying. In view of this finding, caution should be exercised in describing detailed cell surface morphology by SEM when similar preparative procedures are employed.

Inhibitory effect of sheep erythrocyte fragments on rosette formation of human T lymphocytes with sheep red blood cells

The effect of sheep red blood cells (SRBC) fragments on rosette formation of human peripheral T lymphocytes with SRBC was evaluated on the active and total T-rosette tests. The rosetting capacity of active rosette-forming cells was selectively and nearly completely inhibited by the pretreatment of lymphocytes with SRBC fragments. The decrease in total rosettes by blocking with SRBC fragments was almost parallel to that of active rosettes. SRBC fragments had no inhibitory effect on the rosetting capacity of a lymphocyte population in which active rosette-forming cells were removed by gradient centrifugation. These results suggested that active rosette-forming cells in human T lymphocytes have the receptors of high affinity for SRBC and these receptors readily bind SRBC fragments, resulting in block of rosette formation.

Morphological differences in the interactions between human mononuclear cells and coated or uncoated sheep red blood cells: a freeze-etch study of different types of rosettes

Enriched preparations of E, EA and EAC rosettes formed by human peripheral blood mononuclear cells were freeze-etched and examined electron-microscopically. In E rosettes only lymphocyte were involved, whereas in EA and EAC rosettes lymphocytes and mononuclear phagocytes participated as rosette-forming cell. In EA and EAC rosettes, cytoplasmic extensions of the rosette forming cell were seen to penetrate the sheep red blood cell, whereas E rosettes showed a broad zone of adherence without penetration. None of the three types of rosettes showed an interspace between the membranes. Unlike E rosettes, EA and EAC rosettes showed polarity in the adherence of sheep red blood cells. These observations made by freeze-etch electron microscopy indicate distinct morphological differences between rosettes formed with coated or uncoated erythrocytes.

The scanning electron microscopy of normal human peripheral blood lymphocytes

A study of the effects of various sample preparation techniques for scanning electron microscopy has been undertaken in an attempt to resolve conflicting descriptions of the surface topography of human peripheral blood lymphocytes. By fixing cells in suspension--a technique thought most likely to avoid the production of artefacts--no clearly defined morphological classification of lymphocytes could be made, and when T- and B-lymphocyte enriched preparations were studied their surfaces appeared similar. Both T- and B-rosetted cells showed identical morphological changes as a result of their interaction with red blood cells. The smooth cells described in other reports were found only under certain conditions of preparation. It is therefore not possible to distinguish between T- and B-cell populations, using the S.E.M., on the basis of surface morphology alone.

Immunospecific labeling of mouse lymphocytes in the scanning electron microscope

Bone marrow-derived (B) and thymus-derived (T) Balb/c mouse lymphocytes were identified in the scanning electron microscope (SEM) by the immunospecific attachment of one of several kinds of large-molecular-weight markers distinguishable in SEM. These markers (tobacco mosaic virus, keyhole limpet hemocyanin, bushy stunt virus, and bacteriophage T4) could be modified with hapten groups and linked with anti-hapten antibody, in an indirect (sandwich) scheme, to hapten-modified anti-cell-surface antibody bound to the cell surface. Hapten-modified antibodies to B cell antigens (goat anti-mouse-immunoglobulin) or to T cell antigens (rabbit anti-mouse brain) were employed to identify these two lymphoid cell types in unfractionated spleen, mesenteric lymph node, bone marrow, and thymus cell populations. The topography of B cells was always indistinguishable from that of T cells. No surface features were found to be unique to either cell type. In suspension, the majority of B and T cells had one or no microvilli regardless of the tissue source of the labeled cells. Cells in suspension that had microvilli (usually 10% of the total cell population) were always unlabeled. However, after cell contact with a glass surface, approximately half of both the B and T cell population had a villous topography.

Surface features of cells in human lymphoproliferative disorders. An immunoelectron microscopy study

Peroxidase conjugated antibodies were applied to cell suspensions in order to detect surface associated immunoglobulins. Cell suspensions were fixed prior to incubation with reagents, a procedure avoiding membrane alterations induced by antibodies to surface component. By immunoelectron microscopy an identification of B lymphocytes could be made with simultaneous observation of their surface architecture. Basic findings were that normal circulating human B lymphocytes had a villous surface. This relationship was not confirmed however by examinating samples from various B and T cell proliferations establishing that surface morphology is not sufficient to categorize cells in disease. Specimens from hairy cell leukemia were also examined. Despite salient surface characteristics as revealed by the present method, the categorization of cells remains unclear.

E rosette formation by human t lymphocytes: a spontaneous cell mediated cytotoxic phenomenon

The nature and significance of spontaneous association between unsensitized human T lymphocytes and sheep erythrocytes has been studied in relation to a possible cytotoxic reaction. Human lymphocytes and 51Cr labelled sheep erythrocytes when mixed in ratios of 5 or 10:1 released 70-100% of 51Cr into the supernatants. This suggests that E rosette formation may be the first step in a spontaneous T cell mediated cytotoxic reaction to sheep erythrocytes.

A scanning electron microscopy and immunological study of 84 cases of lymphocytic leukaemia and related lymphoproliferative disorders

The surface features of cells from 84 cases of lymphocytic leukaemia, and related lymphoproliferative disorders are described as seen by scanning electron microscopy (SEM). Most of the 46 cases of CLL were shown to be B-derived, but rare cases of mixed B and T cell leukaemia and leukaemia with cells bearing both B and T markers were also encountered. Despite the existence of a spectrum of cell surface morphology, it was possible in many cases to identify a dominant cell type. Cells from cases of B derived malignancies were most frequently of the 'predominantly villous' type while a smaller proportion of cases were of the predominantly 'smoother' or 'mixed villous and smooth' type. Variations in surface morphology also occurred with progression of the disease. In most cases of acute lymphoblastic leukaemia (ALL) 'smoother' cells predominated. However, more cases of ALL and T derived leukaemia need to be examined before definite conclusions can be drawn concerning the surface of these cell types. This study also illustrates the importance of examining large numbers of cases of leukaemia, before conclusions are drawn concerning their surface features and indicates that SEM cannot consistently distinguish between leukaemic B and T cells. It will be of interest to determine whether the surface architecture of the leukaemic cell is related to the degree of cell differentiation and eventual prognosis in these cases.

Scanning electron microscopy of cells from periapical lesions

Examination of lymphocytes from peripheral blood with the scanning electron microscope (SEM) has shown differences between B cells and T cells on the basis of their surface architecture. This study was initiated to determine whether the cellular components of periapical lesions could be identified with the use of similar criteria. Cells were dispersed from lesions by aspiration of fragments of tissue through syringe needles of decreasing diameters. The liberated cells were filtered on silver-coated Flotronic membranes and examined under the SEM. Lymphocytes, macrophages, epithelial cells, and mast cells were observed in granulomas and cysts. Most of the lymphocytes had smooth surfaces similar to that of T cells; others had villous projections similar to that of B cells. Epithelial nests were seen in the cyst linings while the cyst fluid was rich in lymphocytes. These findings suggest that SEM examination of periapical lesions can be a useful adjunct in studying cellular composition and possible immunological reactions in these tissues.

A scanning electron microscopic study of 34 cases of acute granulocytic, myelomonocytic, monoblastic and histiocytic leukemia

This report describes the surface architecture of leukemic cells, as seen by scanning electron microscopy in 34 patients with acute nonlymphoblastic leukemia. Six patients with myeloblastic, 4 with promyelocytic, 10 with myelomonocytic, 8 with monocytic, 4 with histiocytic and 2 with undifferentiated leukemia were studied. Under the scanning electron microscope most leukemia histiocytes and monocytes appeared similar and were characterized by the presence of large, well developed broad-based ruffled membranes or prominent raised ridge-like profiles, resembling ithis respect normal monocytes. Most cells from patients with acute promyelocytic or myeloblastic leukemia exhibited narrower ridge-like profiles whereas some showed ruffles or microvilli. Patients with myelomonocytic leukemia showed mixed populations of cells with ridge-like profiles and ruffled membranes whereas cells from two patients with undifferentiated leukemia had smooth surfaces, similar to those encountered in cells from patients with acute lymphoblastic leukemia. It appears that nonlymphoblastic and lymphoblastic leukemia cells (particularly histiocytes and monocytes) can frequently be distinquished on the basis of their surface architecture. The surface features of leukemic histiocytes and monocytes are similar, suggesting that they may belong to the same cell series. The monocytes seem to have characteristic surface features recognizable with the scanning electron microscope and differ from most cells from patients with acute granulocytic leukemia. Although overlap of surface features and misidentification can occur, scanning electron microscopy is a useful adjunct to other modes of microscopy in the study and diagnosis of acute leukemia.

Human T-lymphocyte rosette formation: inhibition by cytochalasin B

The effects of cytochalasin B, colchicine and vinblastine on the rosette formation of human T lymphocytes with neuraminidase-treated human erythrocytes (nHRBC) and with sheep red blood cells (SRBC) have been studied. Pretreatment of the lymphocytes with cytochalasin B which affects microfilament action reversibly inhibits both nHRBC and SRBC rosette formation. Colchicine and vinblastine known to interact with microtubules causes no major reduction in rosette-forming cells. The results suggest that normally functioning microfilaments are necessary for nHRBC and SRBC rosetting, whereas microtubules are not essential for the blinding of the erythrocytes to the lymphocytes.

Surface features of human eosinophils: a scanning and transmission electron microscopic study of a case of eosinophilia

Cells were obtained from the peripheral blood of a patient with marked non-leukaemic eosinophilia. Transmission electron microscopy (TEM) showed typical mature eosinophils. The surface architecture of eosinophils by scanning electron microscopy (SEM) shows that most were spherical with varying numbers of microvilli; a smaller proportion of cells had ridge-like profiles, small ruffles and occasionally blebs. The surface features of the eosinophil thus resemble most lymphocytes and this finding must be considered when leucocyte populations are examined by SEM.

Biochemical and enzymatic characterization of thymic and splenic lymphocyte plasma membranes from inbred rats

Purified splenic and thymic lymphocytes from the ACI and F344 strains of inbred rats were disrupted by controlled hypotonic treatment, and their plasma membranes were prepared by sucrose density gradient centrifugation. The plasma membrane preparations were highly purified as judged by the structural appearance of the smooth membrane vesicles, by the 10- to 15-fold enrichment of 5'-nucleotidase, which cytochemically localized exclusively in the plasma membranes of intact lymphocytes, by the high cholesterol to phospholipid molar ratio (0.7-1.0), and by the very low specific activities of the enzymes associated predominantly with mitochondria, lysosomes, and endoplasmic reticulum. The protein and the lipid contents of the membranes were 48-55 and 37-48%, respectively. The total lipid content of plasma membranes was characteristically higher in thymic than splenic lymphocytes from both ACI and F344 strains. The specific activity of 5'-nucleotidase was similar in splenic lymphocyte membranes of the ACI strain, and in both the thymic and splenic lymphocyte membranes of the F344 strain. In contrast, the thymic lymphocyte membranes in the ACI strain showed half as much 5'-nucleotidase specific activity. Cytochemical results indicated that the 5'-nucleotidase is located on the outside surface of the lymphocyte plasma membranes.

Human lymphocytes: similarity of B and T cell surface morphology

When viewed by scanning electron microscopy human lymphocytes fixed in suspension and processed with minimal cell loss appear uniformly covered with short microvilli. Contrary to previous reports, lymphocytes from subpopulations selectively enriched for T cells are villous and indistinguishable from B lymphocytes. Whereas lymphocyte surface architecture can change rapidly and substantially in response to environmental modifications, such as contact with an underlying surface, these alterations are similar for both B and T cells and do not serve to distinguish these subpopulations.