Scanning electron microscopy of human lymphocyte-sheep erythrocyte rosettes

Cell surface immunoglobulin. XII. Localization of immunoglobulin on murine lymphocytes by scanning immunoelectromicroscopy

The localization of immunoglobulin (Ig) on the surface of murine splenic lymphocytes has been studied with the scanning electron microscope (SEM), using a rabbit F(ab')2 hybrid antibody directed against mouse Ig and tobacco mosaic virus (TMV) with TMV as a morphological marker. 35% of spleen cells and 3% of thymus cells were labeled by this method. Labeled cells were usually small lymphocytes with moderate numbers of microvilli. The Ig molecules were randomly distributed on the lymphocyte surface, appearing on microvilli as well as on the smooth surface of the cell.

The surface morphology of human B lymphocytes as revealed by immunoelectron microscopy

Surface immunoglobulins (sIg) were detected on human lymphocytes by immunoelectron microscopy with peroxidase-conjugated antibodies. Blood, marrow, and thymus cells from normal individuals and patients with lymphoproliferative disorders were examined. Samples were fixed before exposure to specific reagents. Normal lymphocyts with detectable sIg, i.e. B lymphocytes, were characterized by a villous surface; nonlabeled blood lymphocytes and thymocytes were smooth cells. Intermediate cells were also found which in sections appeared moderately villous and labeled, thus identified as B lymphocytes. Further evidence for a relationship between villous surface and sIg was given by the finding of a few lymphocytes with polar concentration of labeled microvilli. In chronic lymphocytic leukemia patients, most cells exhibited a villous surface with parallel variations of the number of microvilli and of anti-immunoglobulin-binding capacity. However, some labeled smooth blastic cells were also observed. On the other hand, abnormal lymphocytes from Sézary's syndrome which could exhibit segments of villous membrane had no detectable sIg. This study confirms that in most cases human B lymphocytes have a characteristic surface appearance and that the detection of sIg in normal lymphocytes correlates with the presence of microvilli.

Scanning electron microscopy of tobacco mosaic virus-labeled lymphocyte surface antigens

The study of surface antigen by immunoelectron microscopy has been hampered by the fact that thin sections of cells provide only a view of the cell perimeter in an essentially two- dimensional fashion. Although the reconstruction of the entire cell from serial sections has been accomplished (1), it remains too exacting a technique and will find only exceptional application. Carbon-platinum replicas (2) allow the inspection of larger surface areas and therefore are better suited for studying the distribution of antigens (3). But since only relatively smooth surfaces will yield stable replicas, cells with large numbers of microvilli are not amenable to this technique. Despire its limited resolution, scanning electron microscopy (SEM) seems to be the method of choice because it can provide a view of almost half of the surface of a cell close to its natural configuration, particularly after critical point or freeze drying (4, 5). Immunological-labeling methods have not yet been routinely applied to SEM although both latex spheres (6) and hemocyanin (7) have been used with some success. The optimal visual marker should possess the following properties: be of a distinctive shape, chemically stable, and have per se a low binding affinity for cell surfaces. Tobacco mosaic virus (TMV), a marker with which we are familiar in transmission electron microscopy (8), seems to meet these demands; it has rod-like shape and defined dimensions (15 x 300 nm) and in addition it can easily be distinguished from surface microvilli. As the hybrid antibody technique (9) is also applicable to TMV, we have attempted to combine such immunological labeling with SEM. We present evidence that surface antigens can indeed be visualized by SEM, using the TMV marker in conjunction with the hybrid antibody technique.

Surface morphology of murine B and T lymphocytes: A comparative study by scanning electron microscopy

A variety of murine lymphocytes of known B or T derivation obtained from different lymphoid organs were prepared for scanning electron microscopy (SEM) by the critical point drying method after collecting the cells by aspiration onto silver membranes. Comparison of SEM appearances of cells prepared by this technique and serological classification according to surface antigens showed that most T cells had smooth surfaces with few microvilli, while many B lymphocytes were moderately to markedly villous. Further evidence for the above correlation was obtained by examining thymic cells and enriched B or T cell populations. Thymic cell suspensions containing less than 5% B cells showed over 80% generally smooth cells by SEM. Enriched T cell populations, obtained by mass cytolysis of lymph node preparations with anti-Ia or anti-Ig sera or by purification through nylon fiber columns, contained over 85% T cells, and more than 75% of them were of the smooth cell type. A similar correlation was noted for enriched B cell populations obtained by cytolysis of lymph node cells with anti-Thy-1 serum, and by lysis of EAC-rosettes. Over 90% of these cells were identified as B cells by immunologic methods and approximately 75% had moderate to markedly villous surfaces. The 15% difference can be accounted for by the existence of a subpopulation of smooth B cells. Direct observation of EAC-rosettes confirmed that most B cells had moderate to large numbers of surface microvilli and that less than 10% were smooth. It is possible that some of the smooth cells seen in enriched B cell populations may represent precursors or B lymphocytes at different stages of differentiation. These results indicate that murine T and B lymphocytes, like their human counterparts, can be recognized in many cases under the SEM on the basis of their surface morphology. Smoother B and more villous T cells are difficult to classify by SEM without parallel immunologic identification.