Complex immunophenotyping single-cell analysis are essential for systems biology and cytomics.
The application of cytomics in immunology and cardiac research and diagnostics is very broad,
ranging from the better understanding of the cardiovascular cell biology to the identification of heart
function and immune consequences after surgery. TCPC or Fontan-type circulation is an accepted
palliative surgery for patients with a functionally univentricular heart. Protein-losing enteropathy
(PLE), the enteric loss of proteins, is a potential late complication after TCPC surgery. PLE etiology
is poorly understood, but immunological factors seem to play a role. This study was aimed to gain
insight into immune phenotype alterations following post-TCPC PLE. Patients were studied during
routine follow-up up to 5yrs after surgery, blood samples of TCPC patients without (n=21, age
6.8±2.6 years at surgery; mean±SD) and with manifest PLE (n=12, age 12.8± 4.5 years at sampling)
and age matched healthy children (control, n=22, age 8.6±2.5 years) were collected. Routine
laboratory, immune phenotype and serological parameters were determined. Following PLE the
immune phenotype dramatically changed with signs of acute inflammation (increased neutrophil and
monocyte count, CRP, IL-8). In contrast, lymphocyte count (NK-cells, αβTCR+CD4+, αβTCR+CD8+ cells) decreased (p<0.001). The residual T-cells had elevated CD25 and CD69
expression. In PLE-patients unique cell populations with CD3+αβ/γδTCR- and αβTCR+CD4-8-
phenotype were present in increased frequencies. Our studies show dramatically altered leukocyte
phenotype after PLE in TCPC patients. These alterations resemble to changes in autoimmune
diseases. We conclude that autoimmune processes may play a role in etiology and pathophysiology
of PLE.
Shear stress is known to have a significant effect on the state of cellular differentiation. It also induces morphologic responses including changes to cytoskeletal organization subsequently leading to changes in cell shape. In fact, fluid shear stress caused by blood flow is a major determinant of vascular remodeling and can lead to development of atherosclerosis. The morphological changes are usually evaluated using boundary-based shape descriptors or binary geometrical moments on manually segmented cells. Although any one of the many automated segmentation methods could be employed, these techniques are known to be complex and time consuming, and often require user input to operate properly, which is especially problematic for HCS systems. Therefore, development of robust, quantitative morphological measurements that are not dependent on precision and reproducibility of segmentation is extremely important for a substantial improvement of shear-stress analysis. The goals of this study were to find simple morphological descriptors that could be applied to cells isolated by tessellation in order to enable a high-throughput screening of morphological shear-stress response, and to determine the amount of fluid shear stress to which endothelial cells were exposed on the basis of changes in their morphology. The proposed technique is based on the monitoring of changes in cytoskeleton organization using texture descriptors, rather than on quantifying cell-boundary modifications. We showed that objects identified by Voronoi tessellation carried enough information about cytoskeleton texture of individual cells to create a robust classifier. Our approach provided higher discriminant and predictive powers, and better classification capability, than traditional boundary-based methods. The robustness of classification in the presence of segmentation difficulties makes the proposed approach particularly suitable for automated HCS systems.
Scanning Fluorescence Microscope (SFM) is a new technique for automated motorized microscopes to measure multiple fluorochrome labeled cells (Bocsi et al. Cytometry 2004, 61A:1). The ratio of CD4+/CD8+ cells is an important in immune diagnostics in immunodeficiency and HIV. Therefor a four-color staining protocol (DNA, CD3, CD4 and CD8) for automated SFM analysis of lymphocytes was developed. EDTA uncoagulated blood was stained with organic and inorganic (Quantum dots) fluorochromes in different combinations. Aliquots of samples were measured by Flow Cytometry (FCM) and SFM. By SFM specimens were scanned and digitized using four fluorescence filter sets. Automated cell detection (based on Hoechst 33342 fluorescence), CD3, CD4 and CD8 detection were performed, CD4/CD8 ratio was calculated. Fluorescence signals were well separable on SFM and FCM. Passing and Bablok regression of all CD4/CD8 ratios obtained by FCM and SFM (F(X)=0.0577+0.9378x) are in the 95% confidence interval. Cusum test did not show significant deviation from linearity (P>0.10). This comparison indicates that there is no systemic bias between the two different methods. In SFM analyses the inorganic Quantum dot staining was very stable in PBS in contrast to the organic fluorescent dyes, but bleached shortly after mounting with antioxidant and free radical scavenger mounting media. This shows the difficulty of combinations of organic dyes and Quantum dots. Slide based multi-fluorescence labeling system and automated SFM are applicable tools for the CD4/CD8 ratio determination in peripheral blood samples. Quantum Dots are stable inorganic fluorescence labels that may be used as reliable high resolution dyes for cell labeling.
The goal of predictive medicine is the detection of changes in patient's state prior to the clinical manifestation of the deterioration of the patients current status. Therefore, both the diagnostic of diseases like cancer, coronary atherosclerosis or congenital heart failure and the prognosis of the effect specific therapeutics on patients outcome are the main fields of predictive medicine. Clinical Cytomcs is based on the analysis of specimens from the patient by Cytomic technologies that are mainly imaging based techniques and their combinations with other assays. Predictive medicine aims at the recognition of the "fate" of each individual patients in order to yield unequivocal indications for decision making (i.e. how does the patient respond to therapy, react to medication etc.). This individualized prediction is based on the Predictive Medicine by Clinical Cytomics concept. These considerations have recently stimulated the idea of the Human Cytome Project. A major focus of the Human Cytome Project is multiplexed cy-tomic analysis of individual cells of the patient, extraction of predictive information and individual prediction that merges into individualized therapy. Although still at the beginning, Clinical Cytomics is a promising new field that may change therapy in the near future for the benefit of the patients.
Aim: In patients, e.g. with congenital heart diseases, a differential blood count is needed for diagnosis. To this end by standard automatic analyzers 500 μl of blood is required from the patients. In case of newborns and infants this is a substantial volume, especially after operations associated with blood loss. Therefore, aim of this study was to develop a method to determine a differential blood picture with a substantially reduced specimen volume.
Methods: To generate a differential blood picture 10 μl EDTA blood were mixed with 10 μl of a DRAQ5 solution (500μM, Biostatus) and 10 μl of an antibody mixture (CD45-FITC, CD14-PE, diluted with PBS). 20 μl of this cell suspension was filled into a Neubauer counting chamber. Due to the defined volume of the chamber it is possible to determine the cell count per volume. The trigger for leukocyte counting was set on DRAQ5 signal in order to be able to distinguish nucleated white blood cells from erythrocytes. Different leukocyte subsets could be distinguished due to the used fluorescence labeled antibodies. For erythrocyte counting cell suspension was diluted another 150 times. 20 μl of this dilution was analyzed in a microchamber by LSC with trigger set on forward scatter signal.
Results: This method allows a substantial decrease of blood sample volume for generation of a differential blood picture (10 μl instead of 500μl). There was a high correlation between our method and the results of routine laboratory (r2=0.96, p<0.0001; n=40). For all parameters intra-assay variance was less than 7 %.
Conclusions: In patients with low blood volume such as neonates and in critically ill infants every effort has to be taken to reduce the blood volume needed for diagnostics. With this method only 2% of standard sample volume is needed to generate a differential blood picture. Costs are below that of routine laboratory. We suggest this method to be established in paediatric cardiology for routine diagnostics and for resource poor settings.
Immunophenotyping of peripheral blood leukocytes (PBLs) is performed by flow cytometry (FCM) as the golden standard. Slide based cytometry systems for example laser scanning cytometer (LSC) can give additional information (repeated staining and scanning, morphology). In order to adequately judge on the clinical usefulness of immunophenotyping by LSC it is obligatory to compare it with the long established FCM assays. We performed this study to systematically compare the two methods, FCM and LSC for immunophenotyping and to test the correlation of the results. Leucocytes were stained with directly labeled monoclonal antibodies with whole blood staining method. Aliquots of the same paraformaldehyde fixed specimens were analyzed in a FACScan (BD-Biosciences) using standard protocols and parallel with LSC (CompuCyte) after placing to glass slide, drying and fixation by aceton and 7-AAD staining. Calculating the percentage distribution of PBLs obtained by LSC and by FCM shows very good correlation with regression coefficients close to 1.0 for the major populations (neutrophils, lymphocytes, and monocytes), as well as for the lymphocyte sub-populations (T-helper-, T-cytotoxic-, B-, NK-cells). LSC can be recommended for immunophenotyping of PBLs especially in cases where only very limited sample volumes are available or where additional analysis of the cells’ morphology is important. There are limitations in the detection of rare leucocytes or weak antigens where appropriate amplification steps for immunofluorescence should be engaged.
Automated quantitative (i.e. stochiometric) analysis of tissues is of eminent importance in the understanding of all interactions between cells in their natural environment. In tissue cytometry a solid trigger is necessary in order to unequivocally differentiate between cellular and non-cellular events. This can be best performed by nuclear staining. Aim of this study was to analyze a brain tissue section by laser scanning cytometry (LSC) in order to depict the threedimensional distribution of nuclei in the tissue. To this end the section was measured in several foci and different nuclei detected in several depths of the tissue were assigned to the respective layer. Frozen sections of formalin-fixed rat or human brain tissue (120μm thickness) were incubated with propidiumiodide (PI) (50μg/ml) and covered on slides. For analysis by the LSC propidiumiodide was used as trigger. After a first analysis focussed on the top of the tissue, the focus was adjusted in 30μm steps deeper into the tissue. Per analysis data of at least 50,000 cells were acquired. After finishing measurements from all depths of the field were merged, i.e. data were combined into a composite data file.
With the special features of the LSC it was possible to develop a method depicting the threedimensional distribution of the nuclei in solid tissue sections. LSC can be useful tool for this relatively new field of solid tissue cytometry termed tissomics. After evaluation of methods like this, so far not available data can be analysed for diagnostic purposes. By these studies we intend to demonstrate the power of the LSC for the routine pathological use. This should add up to the bright versatility of applications for the LSC as a cytometric instrument suitable for high throughput and high content analysis.
In neurons of patients with Alzheimers's disease (AD) signs of cell cycle re-entry as well as polyploidy have been reported, indicating that the entire or a part of the genome of the neurons is duplicated before its death but mitosis is not initiated so that the cellular DNA content remains tetraploid. It was concluded, that this imbalance is the direct cause of the neuronal loss in AD3. Manual counting of polyploidal cells is possible but time consuming and possibly statistically insufficient. The aim of this study was to develop an automated method that detects the neuronal DNA content abnormalities with Laser Scanning Cytometry (LSC). Frozen sections of formalin-fixed brain tissue of AD patients and control subjects were labelled with anti-cyclin B and anti-NeuN antibodies. Immunolabelling was performed using Cy5- and Cy2-conjugated secondary antibodies and biotin streptavidin or tyramid signal amplification. In the end sections of 20µm thickness were incubated with propidium iodide (PI) (50μg/ml) and covered on slides. For analysis by the LSC PI was used as trigger. Cells identified as neurons by NeuN expression were analyzed for cyclin B expression. Per specimen data of at least 10,000 neurons were acquired. In the frozen brain sections an automated quantification of the amount of nuclear DNA is possible with LSC. The DNA ploidy as well as the cell cycle distribution can be analyzed. A high number of neurons can be scanned and the duration of measuring is shorter than a manual examination. The amount of DNA is sufficiently represented by the PI fluorescence to be able to distinguish between eu- and polyploid neurons.
For immunophenotypic analysis more measurable parameters for the discrimination of leukocyte subsets are necessary. With a single scan six fluorochromes can be distinguished with the Laser Scanning Cytometer (LSC). Due to the number of PMTs the amount of simultaneously measurable fluorescences per scan is limited. Nevertheless, the amount of measurable colors can be improved to eight by appropriate change of the filter settings and two scans per specimen. Aim of this study was to use the special features of Slide based Cytometry (SBC) beyond filter change, remeasurement and merging to distinguish fluorochromes with similar emission spectra. The photosensitivity of fluorochromes that are excited and emit in a similar wavelength range may be very different. The number of measurable parameters per PMT was increased using photosensitivity of different fluorochromes as additional criteria. Peripheral blood leukocytes were stained with antibodies conjugated to the fluorochromes APC, APC-Cy5.5 and Alexa-Fluor 633 and mounted on conventional uncoated glass slides with Fluorescence mounting medium. Specimens were excited in the LSC with the HeNe (633nm) Laser and measured at different filter settings (670/20nm-filter for APC/ALEXA 633 and 710/20nm-filter for APC-Cy5.5). At this point, APC-Cy5.5 and APC/ALEXA633 were already distinguishable. In order to differentiate between APC and ALEXA633 photobleaching was performed by repeated excitation with the laser at 633nm. Control measurements proved that APC is much more sensitive against laser excitation, i.e. looses much more fluorescence intensity than ALEXA633. The separate measurements (before/after filter change and before/after bleaching) were merged into one file. The photostability of Alexa-Fluor 633 (1.02% bleach per scan) and APC (5.74% bleach per scan) are substantially different. Therefore, after bleaching and merging both fluorochromes can be distinguished and are regarded by the software as separate parameters. The fluorochromes APC/ALEXA633 and APC-Cy5.5 can be discriminated by changing the emission filters before bleach. By sequential photobleaching, change of filters and subsequent merging of the data the number of simultaneously measurable “colors” is substantially increased.
Background: Slide based cytometry (SBC) is a technology for the rapid stoichiometric analysis of cells fixed to surfaces. Its applications are highly versatile and ranges from the clinics to high throughput drug discovery. SBC is realized in different instruments such as the Laser Scanning Cytometer (LSC) and Scanning Fluorescent Microscope (SFM) and the novel inverted microscope based iCyte image cytometer (Compucyte Corp.). Methods: Fluorochrome labeled specimens were immobilized on microscopic slides. They were placed on a conventional fluorescence microscope and analyzed by photomultiplayers or digital camera. Data comparable to flow cytometry were generated. In addition, each individual event could be visualized. Applications: The major advantage of instruments is the combination of two features: a) the minimal sample volume needed, and b) the connection of fluorescence data and morphological information. Rare cells were detected, frequency of apoptosis by myricetin formaldehyde and H2O2 mixtures was determined;. Conclusion: LSC, SFM and the novel iCyte have a wide spectrum of applicability in SBC and can be introduced as a standard technology for multiple settings. In addition, the iCyte and SFM instrument is suited for high throughput screening by automation and may be in future adapted to telepathology due to their high quality images. (This study was supported by the IZKF-Leipzig, Germany and T 034245 OTKA, Hungary)
The request for a more profound immunophenotyping and sometimes the lack of material demands more measurable fluorescence colors to increase the number of detectable antigens per specimen. Six different fluorescences are distinguishable in the Laser Scanning Cytometer (LSC). In the present study we wanted to increase this number to eight colors per measurement. Combined with an earlier study it is likely possible to measure n fluorescences i.e. n leukocyte subsets by a series of measurements followed by subsequent restraining steps. The new method is realized by s-ing the combination of filter change and a subsequent re-measurement for the distinction between the fluorescent dyes Cy5 and Cy5.5. The optical filters are replaced after the first measurement and the same specimen is remeasured without removing it from the microscope. For the second measurement a filter is inserted that detects Cy5.5 but not Cy5 (710/10nm). After the second measurement of the same specimen both data files are combined. With the aid of this feature it is possible to line out the differences between both measurements. If the data from the second measuring (Cy5.5 only) is subtracted from the first, Cy5 data is the result. After the first two measurements when eight different fluorescences (i.e. antigens or leukocyte subsets) were analyzed, the same cells are restained and a new measurement is performed. In theory, one can perform n re-measurements with eight fluorescences respectively. The information gained per specimen is only limited by the number of available antibodies and b sterical hindrance.
Increasing evidence suggests, that endothelial progenitor cells (EPC) play an important role in postnatal neovascularization. The formation of new blood vessels is important in many procedures, e.g. embryogenesis, wound healing, tumor growth and neovascularization of ischemic tissue. Aim of this study was to evaluate an assay which is able to detect EPCs qualitatively as well as quantitatively. This was done by Flo cytometry (FCM) and Laser Scanning Cytometry (LSC). Peripheral blood was drawn out of healthy control persons. In Flow Cytometry mononuclear cells of the peripheral blood, KDR and CD34 double positive cells were defined as precursors of EPCs. Cells from the same specimen were cultured and measured by LSC. While measuring with the LSC it was possible to exclude artifacts o debris by controlling the triggering. The specimen measured with FCM and LSC were examined serologically too, regarding cytokines which usually appear with EPCs (e.g. vascular endothelial growth factor [VEGF]). However, measured results had a good correlation, i.e. a higher amount of precursor cells were accompanied with higher EPC counts.
LSC is a microscope-based technology. The principle of the instrument is that any specimen is immobilized on a microscope slide. Therefore the cells are not lost in a fluid stream but are kept on the slide and minimal specimens as low as 1.000 cells can be analyzed. Additionally cells are available for further analyses such as staining for another set of specific markers and re-analysis or cytological staining (H&E). This approach multiplies the information gained from a given sample. We have established an assay for immunophenotyping of peripheral blood leukocytes by LSC. Cells are prepared according to routine flow cytometry protocols with a first set of CD-antibodies and are fixed on microscope slides. As a stable trigger signal the nuclear DNA is stained by 7-aminoactinomycin-D. This guarantees that all nucleated cells and that only nucleated cells are included in the analysis, and many differentiate between lymphocytes and neutrophiles by staining intensity. After analysis cells are stained with a second set of CD-antibodies and analyzed again. This step can be repeated with a third set of CD-antigens. Since the location of the cells on the slide is fixed data from the analyses can be attributed to the same cell.
Cardiac surgery with cardiopulmonary bypass (CPB) alters the leukocyte composition of the peripheral blood (PB). This response contributes to the sometimes adverse outcome with capillary leakage. Migration of activated cells to sites of inflammation, driven by chemokines is part of this response. In order to determine the chemotactic activity of patients serum during and after surgery we established an assay for PB leukocytes (PBL). PBL from healthy donors were isolated and 250,000 cells were placed into a migration chamber separated by a filter from a second lower chamber filled with patient serum. After incubation cells from top and bottom chamber were removed and stained with a cocktail of monoclonal antibodies for leukocyte subsets and analyzed on a flow cytometer (FCM). Cells at the bottom of the filter belong to the migrating compartment and were quantified by LSC after staining of nucleated cells. Increased chemotactic activity started at onset of anaesthesia followed by a phase of low activity immediately after surgery and a second phase of a high post-operative activity. The in vitro results correlated with results obtained by immunopenotyping of circulating PBL. Manipulation of the chemokine pattern might prove beneficial to prevent extravasation of cells leading to tissue damage. In chemotaxis assays with low amount of available serum the combined use of FCM and Laser Scanning LSC proved as an appropriate analytical tool.
In lymphatic organs the quantitative analysis of the spatial distribution of leukocytes would give relevant information about alterations during diseases (leukemia, HIV, AIDS) and their therapeutic regimen. Analysis of them in solid tissues is difficult to perform but would yield important data in a variety of clinical and experimental settings. We have developed an automated analysis method for LSC suitable for archived or fresh biopsy material of human lymph nodes and tonsils. Sections are stained with PI for DNA and up to three antigens using direct or indirect immunofluorescence staining. Measurement is triggered on DNA-fluorescence (Argon Laser). Due to the heterogeneity in cell density measurements are repeatedly performed at different threshold levels (low threshold: regions of low cellular density, germinal centers; high threshold: dense regions, mantle zone). Data are acquired by single- (Ar) or dual-laser excitation (Ar-HeNe) in order to determine data from single- (FITC), up to triple-staining (FITC/PE-Cy5/APC). Percentage and cellular density of cell-subsets is quantified in different structural regions of the specimen. Comparison with manual analysis of identical specimens showed very good correlation. With LSC a semi-automated operator-independent and immunophenotyping of lymphatic tissues with simultaneously up to four antibodies is possible. This technique should yield new insight into processes during diseases and should help to quantify the success of therapeutic interventions.
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