Stereological analysis of the ultrastructure in isolated human T and non-T lymphoid cells. I. Description of method and data on normal blood lymphocytes

Ca2+ signaling in T lymphocytes: the interplay of the endoplasmic reticulum, mitochondria, membrane potential, and CRAC channels on transcription factor activation

T cell receptor stimulation initiates a cascade of reactions that cause an increase in intracellular calcium (Ca2+) concentration mediated through inositol 1,4,5-trisphosphate (IP3). To understand the basic mechanisms by which the immune response in T cells is activated, it is useful to understand the signaling pathways that contain important targets for drugs in a quantitative fashion. A computational model helps us to understand how the selected elements in the pathways interact with each other, and which component plays the crucial role in systems. We have developed a mathematical model to explore the mechanism for controlling transcription factor activity, which regulates gene expression, by the modulation of calcium signaling triggered during T cell activation. The model simulates the activation and modulation of Ca2+ release-activated Ca2+ (CRAC) channels by mitochondrial dynamics and depletion of endoplasmic reticulum (ER) store, and also includes membrane potential in T-cells. The model simulates the experimental finding that increases in Ca2+ current enhances the activation of transcription factors and the Ca2+ influx through CRAC is also essential for the NFAT and NFκB activation. The model also suggests that plasma membrane Ca2+-ATPase (PMCA) controls a majority of the extrusion of Ca2+ and modulates the activation of CRAC channels. Furthermore, the model simulations explain how the complex interaction of the endoplasmic reticulum, membrane potential, mitochondria, and ion channels such as CRAC channels control T cell activation.

T-lymphocyte passive deformation is controlled by unfolding of membrane surface reservoirs

T-lymphocyte passive deformation when squeezing through narrow capillaries is limited by the excess membrane contained in microvilli and membrane folds. During active processes such as transendothelial migration, larger deformations are made possible by an increase in membrane area, possibly through recruitment of internal membrane reservoirs.

T-lymphocytes in the human body routinely undergo large deformations, both passively, when going through narrow capillaries, and actively, when transmigrating across endothelial cells or squeezing through tissue. We investigate physical factors that enable and limit such deformations and explore how passive and active deformations may differ. Employing micropipette aspiration to mimic squeezing through narrow capillaries, we find that T-lymphocytes maintain a constant volume while they increase their apparent membrane surface area upon aspiration. Human resting T-lymphocytes, T-lymphoblasts, and the leukemic Jurkat T-cells all exhibit membrane rupture above a critical membrane area expansion that is independent of either micropipette size or aspiration pressure. The unfolded membrane matches the excess membrane contained in microvilli and membrane folds, as determined using scanning electron microscopy. In contrast, during transendothelial migration, a form of active deformation, we find that the membrane surface exceeds by a factor of two the amount of membrane stored in microvilli and folds. These results suggest that internal membrane reservoirs need to be recruited, possibly through exocytosis, for large active deformations to occur.

Carotenoids located in human lymphocyte subpopulations and natural killer cells by Raman microspectroscopy

The presence and subcellular location of carotenoids in human lymphocyte subpopulations (CD4+, CD8+, T-cell receptor-gamma delta+, and CD19+) and natural killer cells (CD16+) were studied by means of Raman microspectroscopy. In CD4+ lymphocytes a high concentration (approximately 10(-3) M) of carotenoids was found in the Gall body. In CD8+ lymphocytes, T-cell-receptor-gamma delta+ lymphocytes and in natural killer cells carotenoids appeared to be concentrated (approximately 10(-4) M) in the Golgi complex. The concentration of carotenoids in CD19+ lymphocytes was found to be below the present detection limit, which is approximately 10(-6) to 10(-5) M. The results provide new possibilities to investigate the mechanism(s) behind the suggested protective role of carotenoids against the development of cancers.

Ultrastructural morphometry of human leucocytes in health and disease

In this review, the literature on ultrastructural morphometry of each of the main types of human blood leucocytes has been considered, together with the technical and numerical procedures essential for valid analysis. Quantitative data have been reported for these cell types in health and comparisons have been made with those in disease states. In monocytes, and in macrophages developing from them, subtle ultrastructural differences have been detected and quantitated in malignant lymphoma; as the mononuclear phagocytes were not themselves neoplastic, the changes may have related to defects in host defence. Change in the ultrastructural characteristics of leukaemic monoblasts have also been reported. Lymphocytes and malignant lymphoid cells have been extensively investigated: differences between different types and subsets have been shown to be present in both normal lymphocytes and their malignant counterparts in leukemias and lymphomas. Particular attention has been paid to morphometric assessment of nuclear shape and size in these disorders and to its possible value as a diagnostic tool. Granulocytes have so far been the subject of few morphometric studies, although in hypereosinophilic syndrome, cellular changes have been defined and have thrown light on the abnormal pattern of degranulation. There have also been scattered reports on the cells of acute myelogenous leukaemia. The use of computers and sophisticated statistical packages has greatly facilitated the application of multiple comparison procedures and has permitted discriminant analysis to be carried out where appropriate. This review shows that ultrastructural morphometry of leucocytes will have an increasing application in clinical pathology.

Non-Hodgkin's lymphoma classification: ultrastructural morphometric studies for the quantification of nuclear compartments in situ

The condensed chromatin distribution in the nuclei of lymphocytes in non-Hodgkin's lymphoma (NHL) is a key element, along with nuclear size and shape, in the classification of this disease for therapeutic and prognostic purposes. This report describes the ultrastructural comparative quantification of the condensed chromatin and the interchromatinic (nuclear matrix or euchromatin) region in the nuclei of mitogen-stimulated human peripheral T lymphocytes and mouse spleen B lymphocytes, human germinal center lymphocytes, and lymphocytes in ten cases of NHL of a variety of subtypes. The sequential morphologic nuclear changes induced in lymphocytes by mitogens are reflected in human germinal center lymphocyte populations. The common features include the changes in the distribution and volume of condensed chromatin aggregates, as well as the fact that the major increments in nuclear volume during lymphocyte transformation result from increases in the volume of the interchromatinic region. In all subtypes of NHL analyzed morphometrically, subpopulations of lymphocytes were identified in which mean nuclear, condensed chromatin, and interchromatinic volumes were more or less equivalent to those of normal lymphocyte subsets in germinal centers in reactive hyperplasia. However, in NHL the abnormal cytologic characteristics of the nucleus result, at least in part, from a complex interplay of condensed chromatin distribution and amount, and the size of the interchromatinic region. Further complexity is introduced by the fact that in NHL these two nuclear compartments can independently be normal, increased, or reduced in size. Morphometric quantification of lymphocytes in NHL indicates that the interchromatinic (matrix) region of the nucleus is the key element in establishing the nuclear volume of neoplastic lymphocytes. The structural and functional, ribonucleoprotein interchromatinic region of the nucleus was visualized in normal and neoplastic lymphocytes by regressive uranyl-EDTA staining. Quantitative morphometric analysis indicates that the cytologic appearance of neoplastic lymphocytes, even within subtypes of NHL, is heterogeneous and that condensed chromatin quantity and distribution may be more critical than nuclear size in distinguishing between certain subtypes of NHL. Improvements in the classification of NHL will occur only with understanding of the alterations in the biologic mechanisms controlling gross nuclear organization and the morphologic events of the various differentiation pathways available to antigen-stimulated lymphocytes.

Quantitative ultrastructure of cytolytic lymphocytes mediating allograft rejection in the mouse. I. Cellular alterations in T lymphocytes during specific target cell lysis

A quantitative ultrastructural analysis of cytolytic T lymphocytes (CTL) is presented which allows both the distinction of these cells from normal T lymphocytes and permits the demonstration of ultrastructural alterations of putative CTL following interaction with target cells (TC). Alloreactive CTL were generated in C57BL/10 mice receiving intraperitoneal fibroblastic allografts and target-binding splenic lymphocytes (TBSL) were concentrated by specific immunoadsorption on fibroblast monolayers. TBSL were subjected to ultrastructural quantification either at the onset of TC interaction or following 30 or 60 min incubation at 37 degrees C. By means of simple stereological relationships it was shown that, in comparison with normal, non-cytolytic splenic T lymphocytes, TBSL were slightly larger cells, displaying around 60% more cytoplasm, a similarly-sized nucleus and approximately triple the volume of Golgi apparatus. During the first 30 min of interaction with TC, the target binding surface of the TBSL plasma membrane decreased in area. This change was accompanied by a polarization of the TBSL towards the target. Incubation of lymphocytes with TC for a further 30 min resulted in a general polarization of lymphocytic cellular constituents away from the TC. These results were only attainable by objective quantitative analysis and are discussed in relation to possible mechanisms of CTL-mediated lysis.

Stereological analysis of non-Hodgkins lymphomas

A detailed stereological analysis was carried out on 30 lymph nodes at 2 ultrastructural levels. They were classified as follows: 10 were reactive lymph nodes, 10 were of low-grade non-Hodgkins lymphomas and 10 were of high-grade non-Hodgkins lymphomas. The mean and median values and interquartile ranges of nuclear profile diameter, nuclear volume, volume of cytoplasm, cell volume and absolute number of ribosomes were recorded for each case. The model proved very efficient in establishing several significant differences between the highgrade and lowgrade lymphomas and between the highgrade lymphomas and reactive lymph nodes but did not discriminate between lowgrade lymphomas and reactive nodes, nor did it distinguish neoplastic cells from reactive cells in the neoplastic group. The significance of these findings is discussed.

Breast tumour as a first manifestation of extramedullary relapse in acute lymphoblastic leukaemia

After 2 years of maintained complete remission, a 17-year old girl suffering from common acute lymphoblastic leukaemia (C-ALL) developed a mass in the right breast. Determination of the tumour cell phenotype using a panel of monoclonal antibodies demonstrated the presence of leukaemic blasts. At this stage no other sign of relapse could be demonstrated. Later, however, when the leukaemia progressed despite aggressive treatment, blasts with the same surface phenotype as the ones in the breast were obtained both from repeated biopsies from a mediastinal mass and from a lower abdominal mass. Manifestation of first relapse in ALL presenting as a breast tumour has never been described before and may be added to other unusual extramedullary sites of relapse. The significance of immunologically defined phenotyping of cells from tissue biopsies is underlined.

Ultrastructural localization of acid alpha-naphthylacetate esterase in human normal and neoplastic lymphocytic and monocytic cells and in hairy cells

The ultrastructural localization of acid alpha-naphthylacetate esterase (ANAE) activity was studied in normal and neoplastic human monocytic and lymphocytic cells including hairy cells. Normal monocytes and malignant monocytic cells from cases of AML-M4 and -M5 (FAB-classification) displayed fundamentally the same ANAE staining pattern with reaction products localized to the external surface of the plasma membrane and to small vesicles close to this membrane, more rarely to larger intracytoplasmic vesicles containing endocytosed material or cellular debris. The enzyme activity of the neoplastic cells increased with morphological differentiation. Certain normal blood lymphocytes and T cell-derived CLL cells showed the reaction product associated with paranuclearly located clusters of vesicular structures, extending from the membranes into the adjacent cytoplasm. Gall bodies were often found in the vicinity and were invariably positive for ANAE. Now and then, plasma membrane activity was present, but never as pronounced as in monocytes. Hairy cells demonstrated a pattern of reaction very similar to that of monocytic cells, whereas B cell-derived CLL cells and lymphoblasts of T- and common type ALL were generally non-reactive.

Acid phosphatase and acid esterase activity in neoplastic and non-neoplastic lymphoid cells. A semiquantitative evaluation related to immunological markers in 112 cases

Acid phosphatase (AcP) and acid alpha-naphthylacetate esterase (ANAE) were examined in lymphoid cells from 104 patients suffering from various lymphoproliferative disorders and from 8 healthy controls. Enzyme activities were evaluated by means of a scoring system. Scores of AcP and ANAE were higher in normal T cells than non-T cells. In comparison, the activated T cells in infectious mononucleosis showed increased AcP and decreased ANAE reaction. Malignant T lymphoblasts had a distinct granular AcP positivity in contrast to the faint reactivity observed in cALL blasts, whereas ANAE showed negative or weak reaction in both subsets. High scores and distinct staining patterns for both enzymes were found in T CLL and T prolymphocytic leukaemia, clearly different from the weak activities seen in B CLL, B PLL and some B cell lymphomas. The latter, too, could be distinguished by mutual differences in enzyme reactions. High AcP and ANAE scores were also found in hairy cell leukaemia, and the staining patterns together with the tartrate resistance firmly established the diagnosis. Thus, simultaneous determinations of AcP and ANAE can be of great value in the diagnosis of lymphoid malignancies.

Stereologic analysis of the ultrastructure of isolated human T and non-T lymphoid cells. III. Studies in chronic lymphoid leukemias, hairy cell leukemia and some malignant lymphomas

Malignant cells from 9 cases of chronic lymphocytic leukemia (CLL), 4 cases of prolymphocytic leukemia (PLL), 4 cases of hairy cell leukemia (HCL), 4 cases of malignant lymphoma of centrocytic type and 3 cases of malignant lymphoma of lymphoblastic type (Kiel classification), all examined for T and B markers, were analysed by electron microscopy. Stereological methods were applied to assess relative and absolute values concerning the whole cell and nuclear and cytoplasmic components of the average cell in each population, and comparisons were made between the morphologically and immunologically defined subsets. The CLL-lymphocyte possessed the smallest cell volume, a high nucleo-cytoplasmic volume ratio, densely packed heterochromatin, a small nucleolar volume and a sparse Golgi complex. The 7 B-derived cases were characterized by a larger volume of rough ER and a more irregular plasma membrane than the two T-derived cases, which typically displayed dense granules in paranuclear aggregations. The prolymphocyte could be distinguished from the CLL-cell by its larger cell volume, lower nucleo-cytoplasmic volume ratio, proportionally lesser heterochromatin, typically condensed at the periphery and around a prominent nucleolus. All 4 cases of PLL were of B-nature and shared the features of B-CLL regarding increased rough ER and low content of granules. The hairy cell exhibited the largest cell volume, the lowest nucleo-cytoplasmic volume ratio, an indented nucleus and a remarkable irregular cellular surface with long "hairy" processes. The cytoplasmic inclusions of ribosome-lamella complexes were recorded exclusively in hairy cells, in half of the patients. The centrocyte was characterized by a cell volume of intermediate size, a high nucleo-cytoplasmic volume ratio and the highest degree of nuclear irregularity recorded. The amount of rough ER was considerably less than in B-CLL and B-PLL. Finally, the blast from the cases of lymphoblastic lymphoma, all of T-nature, displayed a smooth plasma membrane, a high euchromatin-heterochromatin volume ratio and dense granules, characteristically clustered in the vicinity of the Golgi complex. Stereology on the ultrastructure of malignant lymphoid cells provides a more accurate characterization and may be helpful in classification.

Stereologic analysis of the ultrastructure in isolated human T and non-T lymphoid cells. II. Data on blasts in ALL; correlation with immunologic studies and FAB-morphology

Leukemic cells from 20 cases of acute lymphoblastic leukemia (ALL), examined for T and B markers and classified according to FAB guidelines, were analyzed by electron microscopy. Using stereologic methods a quantitative morphologic characterization of the average blast, assumed to be of clonal origin and thus representative of the whole population, was obtained within each subset. Comparative studies of the ultrastructure of the T, B and non-T, non-B blast on one hand and of the FAB category L1 and L2 on the other were performed. No differences of cell volumes, total cell surface areas, nuclear volumes and surface areas or volumes of nuclear compartments were observed between the immunologically defined subsets. Minor variations were seen in the cellular surface contour, the B blast tending to be more irregular than the T blast. Features most predictive of the immunologic cell type were abundant rough ER in B-derived ALL, increasing with plasmacytoid differentiation, and an increase in dense granules which were often clustered in the vicinity of a well-developed Golgi complex in T ALL. The light microscopic criteria of the FAB classification were nearly all confirmed at the EM-level except that nuclear irregularity was observed to the same degree in both categories. Other differences not related to the FAB scheme were encountered in the volumes of the Golgi complex and of the mitochondrial compartment. Objective criteria as quantitative estimates of cellular structures may contribute to an improved subclassification in ALL.

Ultrastructure of normal human blood T lymphocyte subsets isolated by cell sorting using monoclonal antibodies. A stereological analysis

In continuation of a previous study, the quantitative fine structural characteristics of the average normal human pan-T lymphocyte and its subsets in the peripheral blood has been established using stereological methods. T cell subpopulations were isolated and identified by means of monoclonal T3, T4 and T8 antibodies and a fluorescence-activated cell sorting machine. Comparative studies on ultrastructural morphology were made between the E-rosetting lymphocyte and the T3-positive cell, both markers of the pan-T cell, and between the functionally different T4- and T8-reactive subsets, defining the helper/inducer and suppressor/cytotoxic T cell subpopulation respectively. No significant differences were recorded between the E-rosetting and the T3+ lymphocyte except for minor deviations regarding the surface of the plasma membrane. In comparison with the T4+ lymphocyte, the T8+ cell showed a larger cell volume and cell surface area and decreased nucleo/cytoplasmic volume and surface ratios. The increase in cell size was the result of greater volumes of residual cytoplasm as well as of intracytoplasmic organelles, such as mitochondria, RER, Golgi apparatus and granules, whereas nuclear parameter estimates were concordant. The structural deviations between the T4+ and the T8+ subsets are discussed in the context of their different functional capacity as helper and suppressor/cytotoxic cells.