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Recognition of central nervous system leukemia by flow cytometry.

Cerebrospinal fluid of 24 patients with acute leukemia was studied by DNA/RNA flow cytometry. In six of 15 patients with central nervous system (CNS) relapse, the spinal fluid cells had abnormal DNA stemlines, ranging from near haploid to hyperdiploid. In two additional cases, leukemic cells were identified by a abnormally high RNA content only. One patient had two different aneuploid cell populations in spinal fluid not distinguished by cytologic morphology. Another patient with initial diploid leukemia had CNS relapse characterized by the same DNA stemline long after a triploid DNA stemline emerged in the marrow. DNA/RNA flow cytometry detected leukemic cells that were not identified ("uniform" or "reactive") by cytological criteria in 5/6 patients studied and in addition differentiated lymphoblastic from nonlymphoblastic cell types according to low and high RNA content.

DNA, Neoplasm↗

Clinical applications of flow cytometry in hematology and immunology.

Rapid developments in computer technology combined with new fluorescent dyes and monoclonal antibody production have led to the development of a powerful tool: flow cytometry. The techniques of flow cytometry can be applied in a wide clinical field, from routine tasks to research in immunology and hematology. The availability of automated instruments and standardized sample preparation methods have led to its daily clinical use, helping diagnosis, prognosis or monitoring therapy. Further advances will be made with the introduction of multi-parametric analysis ie quantification of antigen expression of cell surface antigens.

Acquired Immunodeficiency Syndrome↗

Single cell analysis of phosphoinositide 3-kinase/Akt and ERK activation in acute myeloid leukemia by flow cytometry.

BACKGROUND AND OBJECTIVES: Abnormal activation of several signal transduction pathways such as phosphoinositide 3-kinase (PI3K) and MAP kinases has been reported in acute myeloid leukemia (AML). To test new targeted therapeutics, it is critical to develop sensitive analytical tools to detect abnormal activation of these pathways and to monitor their inhibition in response to treatment. DESIGN AND METHODS: We analyzed Akt and ERK phosphorylation in 32 samples from patients using western blot and a two-color flow cytometry protocol using CD34. To circumvent the CD34 negative AML found in our series, we developed a two-color protocol using CD45 to isolate the blast cell population. Finally, a four-color protocol was used to detect phosphorylation in an enriched population of AML stem cells. RESULTS: We compared western blot analysis and flow cytometry for the detection of PI3K/Akt and ERK activation and found a 100% correlation between the two techniques in a series of 32 AML samples. Using a flow cytometry protocol, we were able to analyze all the patients' samples, even those with low blast infiltration or CD34 negative blast cells. We were also able to detect the phosphorylated proteins in the most immature blast cell population with the CD34+ CD38-/low CD123+ phenotype. Interpretations and CONCLUSION: Our study shows that flow cytometry is a reliable method for detecting Akt and ERK phosphorylation in all patients' samples. Activation can also be detected in the most immature blast cells, which represent exquisite target cells for new therapeutics.

Acute Disease↗

Intracellular compounds quantification by means of flow cytometry in bacteria: application to xanthan production by Xanthomonas campestris.

The use of flow cytometry (FCM) to quantitatively analyze intracellular compounds is studied. FCM is a very useful technique for individual cell studies in microbial systems, and gives access to information which cannot be obtained in any other way. Nevertheless, it provides data in arbitrary units, that is, relative data. This analytical technique could be employed for kinetic modeling of microbial systems and even for internal phenomena analysis, but for this purpose, absolute data-that is concentration of intracellular compounds-must be used. In this work, relative flow cytometry data are transformed into absolute data by means of calibrations employing the same fluorochromes with another technique: spectrofluorymetry. Calibrations of DNA, RNA, and protein intracellular concentrations are presented for the bacteria, Xanthomonas campestris. Other analytical methods, based on biochemical determinations, were also employed to quantify intracellular compounds, but the results obtained are very poor compared with those achieved by means of spectrofluorymetry (SFM). Calibration equations and data obtained by both techniques are given. Evolutions of protein and nucleic acids during Xanthomonas campestris growth and xanthan gum production are shown.

Bacterial Proteins↗

Flow cytometry in conjunctival impression cytology: a new tool for exploring ocular surface pathologies.

Flow cytometry (FCM) is a widely used technique, not only in immunology and hematology but also in many other domains and new applications have been developed in ophthalmology, for investigating ocular surface biology and pathophysiology. Apoptosis, proteins specific of cell lineage, expression of activation or immune-related markers, proinflammatory cytokine production, multi-drug resistance and oxidative stress are some examples of possible pathways that may be explored directly using ocular surface cells removed with the non-invasive technique of impression cytology, by means of flow cytometry. Conjunctival cells are thus collected by impression cytology on a filter, fixed in paraformaldehyde and dissociated by agitation before immunostaining and FCM processing. Important observations have been made concerning Sjögren's syndrome, ocular allergy and antiglaucoma eye drop toxicity. Studies performed on impression cytology with FCM techniques confirmed inflammatory and apoptotic patterns in a large number of patients with keratoconjunctivitis sicca or receiving long-term treatments with antiglaucoma drugs, even though they did not present any clinical signs of inflammation. FCM may now be used for large multicenter clinical trials and has already contributed to a better understanding of ocular surface pathophysiology, the monitoring of new immunomodulating drugs and knowledge concerning topical drugs, as regards both efficacy and safety.

Biopsy↗

Detection of anti-phosphatidylethanolamine antibodies using flow cytometry.

BACKGROUND: The finding that lupus anticoagulant (LA) is significantly associated with anti-phosphatidylethanolamine (PE) activity has led to great interest in its relation to the clinical features of the antiphospholipid syndrome (APS). Considerable variability has, however, been reported in the prevalence of anti-PE antibodies in APS patients using enzyme-linked immunosorbent assay (ELISA) methodology. The lack of standardization and differences in technique may in part explain these discrepancies. PE binds variably to different types of microtiter wells, reflected in the consequent detection, or lack of detection, of anti-PE antibodies. This study describes the use of flow cytometry as an alternative method for the detection of anti-PE antibodies. METHODS: Six LA-positive plasma samples were used in this original study. Polystyrene beads were coated with PE overnight. These were subsequently incubated with patient plasma. Both IgG and IgM binding were detected by flow cytometry using a cocktail of fluorescently labelled anti-human Ig isotypes. RESULTS: When these results were compared with those from ELISA, flow cytometric analysis provided an apparent enhanced detection of anti-PE antibodies. It was found that 6/6 were IgM anti-PE positive by flow cytometry, whereas 5/6 were IgM by ELISA; 2/6 negative for anti-cardiolipin antibodies by ELISA were positive by flow cytometry; and 2/6 positive for antiphosphatidylcholine antibodies in cytometry were negative by ELISA. CONCLUSIONS: With appropriate quantification, this method may be more sensitive than ELISA in detecting anti-PE antibodies in plasma samples of patients with APS.

Antibodies, Antiphospholipid↗

Flow cytometry of fetal adrenal glands with adrenocortical cytomegaly.

Adrenal glands from four autopsied fetuses of 18 to 36 weeks gestation showed varying degrees of cortical cytomegaly. Formalin-fixed, paraffin-embedded sections from these four pairs of glands were studied by flow cytometry to analyze their DNA content and cell cycle parameters. Flow cytometry of Case 1, which had diffuse bilateral cytomegaly, demonstrated a major diploid peak, an increased percentage of tetraploid cells, and a decrease in S phase compared to an age-matched control with no evidence of cytomegaly (Case 2). Cases 3, 4, and 5 showed focal and/or unilateral adrenocortical cytomegaly and were diploid by flow cytometry with no differences in synthetic or tetraploid fractions compared to the control tissues. The focal distribution of the lesions or the limits of resolution of the instrumentation could account for some of these results. However, the findings in Case 1 suggest that the cytomegalic cells are tetraploid in DNA content and may have decreased DNA synthetic activity. A current hypothesis that these cells have undergone a period of sustained hyperactivity followed by exhaustion in reaction to an unknown stimulus is supported by our observations.

Adrenal Cortex↗

Quantitation of human anti-mouse antibody in serum by flow cytometry.

Clinical investigations utilizing murine monoclonal antibodies require techniques for the detection of the human anti-mouse antibody (HAMA) response in patient serum. We report here a flow cytometric assay for the quantitation of HAMA. Commercially available beads conjugated with goat anti-mouse antibody provide a solid phase matrix for a triple bridge immunoassay. The measurement of fluorescein labeled antibodies by flow cytometry allows accurate quantitation of the HAMA. The assay will detect antibody levels of approximately 1.0 ng/ml. Antibody recovery in serum samples with known amounts of antibody added was greater than 90% at levels greater than or equal to 10 micrograms/ml. Serum samples obtained from 41 patients prior to and after single or multidose infusions of KS1/4-Desacetyl-vinblastine were analyzed. These results were compared with HAMA titers previously determined by ELISA. With few exceptions, patients with low titers as determined by ELISA demonstrated low HAMA potencies by flow cytometry and those with highest titers the highest potencies. Patients with no detectable HAMA by ELISA were also negative by flow analysis. The results of our studies demonstrate that HAMA levels can be accurately and quantitatively determined by flow cytometry.

Animals↗

Determination of DNA content of aquatic bacteria by flow cytometry.

The distribution of DNA among bacterioplankton and bacterial isolates was determined by flow cytometry of DAPI (4',6'-diamidino-2-phenylindole)-stained organisms. Conditions were optimized to minimize error from nonspecific staining, AT bias, DNA packing, changes in ionic strength, and differences in cell permeability. The sensitivity was sufficient to characterize the small 1- to 2-Mb-genome organisms in freshwater and seawater, as well as low-DNA cells ("dims"). The dims could be formed from laboratory cultivars; their apparent DNA content was 0.1 Mb and similar to that of many particles in seawater. Preservation with formaldehyde stabilized samples until analysis. Further permeabilization with Triton X-100 facilitated the penetration of stain into stain-resistant lithotrophs. The amount of DNA per cell determined by flow cytometry agreed with mean values obtained from spectrophotometric analyses of cultures. Correction for the DNA AT bias of the stain was made for bacterial isolates with known G+C contents. The number of chromosome copies per cell was determined with pure cultures, which allowed growth rate analyses based on cell cycle theory. The chromosome ratio was empirically related to the rate of growth, and the rate of growth was related to nutrient concentration through specific affinity theory to obtain a probe for nutrient kinetics. The chromosome size of a Marinobacter arcticus isolate was determined to be 3.0 Mb by this method. In a typical seawater sample the distribution of bacterial DNA revealed two major populations based on DNA content that were not necessarily similar to populations determined by using other stains or protocols. A mean value of 2.5 fg of DNA cell(-1) was obtained for a typical seawater sample, and 90% of the population contained more than 1.1 fg of DNA cell(-1).

Animals↗

Comparison of image analysis of imprints with flow cytometry for DNA analysis of solid tumors.

Quantitative analysis of cellular DNA content may be clinically useful for several solid tumors. The technology for this analysis by flow cytometry or image analysis has existed for several years but has not been widely used, except in a handful of specialized research institutions. Recently, however, relatively inexpensive image analyzers intended for use by hospital pathologists have been introduced that can analyze DNA content from cytology or imprint specimens which are readily obtainable from solid tumors. We report here an assessment of this technology for analysis of tumor imprint specimens, using flow cytometry of tissue blocks as the standard for comparison. We used image analysis equipment on Feulgan-stained imprint preparations from 31 tumors and compared the histograms with those obtained by flow cytometric analysis of archival tissue blocks from the same tumors. The ploidy descriptors (diploid, tetraploid, and aneuploid) were concordant for the two methods in 27 specimens, with three specimens yielding discordant results and one specimen considered unevaluable by image analysis. The image analysis method using imprints appeared to have several advantages over flow cytometry, including lower instrument cost, no need to dissociate paraffin blocks or fresh tissue, and ability to analyze very small samples. Somewhat lower resolution of the histograms, extremely localized tissue sampling, and possibly greater risk of occasionally obtaining unevaluable preparations were disadvantages. Microcomputer-based image analysis performed on imprints appeared to be a viable alternative to flow cytometric analysis of tissue blocks for quantitative DNA analysis of tumor specimens.

Aneuploidy↗

Quantification of fetomaternal hemorrhage by fluorescence microscopy is equivalent to flow cytometry.

BACKGROUND: The quantification of fetal cells in the maternal circulation remains an important goal to determine the amount of anti-D necessary to prevent active immunization of a D- mother giving birth to a D+ baby. Underestimation of fetomaternal hemorrhage (FMH) results in inefficient anti-D prophylaxis and maternal immunization; overestimation of FMH results in higher doses of passively transferred anti-D, higher costs, and the risk of disease transmission. Thus, a reliable method to quantitatively assess FMH is necessary. STUDY DESIGN AND METHODS: Serial dilutions of artificial FMH were quantitatively measured by three different methods: flow cytometry, fluorescence microscopy (each after anti-D staining), and by the Kleihauer-Betke test. The accuracy and precision of the three methods were compared by statistical analysis. RESULTS: Fluorescence microscopy and flow cytometry were comparably accurate and precise in quantifying FMH. In contrast, the accuracy of the Kleihauer-Betke test was poor, resulting in substantial overestimation of FMH in the samples with lower fetal cell concentrations. CONCLUSION: Anti-D flow cytometry and fluorescence microscopy for detection of fetal cells offer equally reliable and precise methods in contrast to the Kleihauer-Betke test. Fluorescence microscopy may be established as standard to quantify FMH in clinical practice because it is comparable to flow cytometry; in addition, it is time saving and is less expensive.

Adult↗

Measurement of nuclear factor-kappa B translocation on lipopolysaccharide-activated human dendritic cells by confocal microscopy and flow cytometry.

BACKGROUND: Nuclear factor kappa B (NF-kappaB) is a ubiquitously expressed transcription factor that regulates cytokine and immunoglobulin (Ig) gene expression. In most cell types, the inactive p50/p65 NF-kappaB heterodimer is located in the cytoplasm, complexed to its IkappaB inhibitory unit. Stimulation of cells by various reagents such as bacterial endotoxin or cytokines leads to a dissociation of NF-kappaB from IkappaB and a rapid translocation of free NF-kappaB to the nucleus. The aim of this article is to define optimal conditions for the measurement of NF-kappaB translocation by both confocal microscopy and flow cytometry. METHODS: Four commercial anti-NF-kappaB antibodies were evaluated by confocal microscopy, after using two methods of fixation and permeabilization of the cells. These antibodies were examined further by flow cytometry on purified nuclei. RESULTS: Paraformaldehyde-methanol treatment of dendritic cells is a good combination to visualize NF-kappaB translocation by confocal microscopy. Three of the four antibodies tested gave good results on nonactivated and on lipopolysaccharide (LPS)-activated dendritic cells. The measurement of NF-kappaB translocation by flow cytometry on purified nuclei is a quick and sensitive method. Only one of the four evaluated antibodies showed a significant difference between nonactivated and activated cells. CONCLUSIONS; Microscopy and flow cytometry are quick and reproducible methods to measure NF-kappaB translocation and can be adapted to identify new molecules that activate dendritic cells.

Animals↗

Tumour heterogeneity of DNA cell cycle variables in breast cancer measured by flow cytometry.

AIM/BACKGROUND: Conflicting results have been reported concerning the prognostic value of DNA flow cytometric variables (DNA ploidy, DNA index, %S phase fraction) in breast cancer. Selection bias and differences in treatment may have contributed to these conflicting prognostic results. Differences in tissue processing, the number of nuclei measured, DNA histogram/cell cycle analysis, and intra-tumour heterogeneity may also have played a role. The aim of the present study was to assess intra-tumour heterogeneity of DNA flow cytometric variables in breast cancer. METHODS: Fresh frozen specimens (n = 274) (0.3 x 0.3 x 0.3 cm) of 17 breast cancers and 167 slices, 50 microns thick, of 58 paraffin wax embedded blocks of 21 breast cancers were studied. All samples were prepared individually for DNA flow cytometry. DNA histograms were interpreted by semi-automated cell cycle analysis (MultiCycle) by two observers to avoid biased interpretation. An artificial averaged DNA histogram of each case was composed to simulate a sample prepared from whole tumour tissue. RESULTS: With regard to DNA ploidy, classified as diploid or aneuploid, the fresh frozen and paraffin wax embedded breast cancers showed intra-tumour heterogeneity in 53% and 38% of cases, respectively. For fresh frozen and paraffin wax embedded material, respectively, six samples had to be measured to detect the highest DNA ploidy class in 71% and 86% of cases. Averaged DNA histograms showed a loss of DNA aneuploidy in 36% and 6% of fresh frozen and paraffin wax embedded samples, respectively. High intra-tumour heterogeneity (wide ranges) was found for the %S phase fraction. Average %S phase fraction and average aneuploid %S phase fraction had the widest ranges at 9.5-31.6% and 0.0-62.7%, respectively. There was no correlation between the number of stemlines and intra-tumour %S phase variability on the one hand and tumour size and grade on the other. CONCLUSIONS: High intra-tumour heterogeneity for breast cancer was found for DNA ploidy, the DNA index and %S phase fraction as measured by flow cytometry, which may explain the conflicting prognostic results reported in the literature. To detect aneuploid cells, six samples may have to be prepared and measured separately. Measurement of these variables may be more reliable in paraffin wax sections because the thick slices provide a more representative sample. Prospective studies are required to determine whether the highest %S phase fraction value or the average value is more useful in the clinical context.

Breast Neoplasms↗

Comparative analysis of flow cytometry and polymerase chain reaction for the detection of minimal residual disease in childhood acute lymphoblastic leukemia.

Minimal residual disease (MRD) is an independent prognostic factor in childhood acute lymphoblastic leukemia (ALL). The most widely applied MRD assays in ALL are flow cytometric identification of leukemia immunophenotypes and polymerase chain reaction (PCR) amplification of antigen-receptor genes. We measured MRD by both assays in 227 patients with childhood B-lineage ALL. Of 1375 samples (736 bone marrow and 639 peripheral blood) examined, MRD was <0.01% in 1200, and > or =0.01% in 129 by both assays; MRD levels measured by the two methods correlated well. Of the remaining 46 samples, 28 had MRD > or =0.01% by flow cytometry but <0.01% by PCR. However, PCR (which had a consistent sensitivity of 0.001%) detected leukemic gene rearrangements in 26 of these 28 samples. Conversely, in 18 samples, MRD was > or =0.01% by PCR but <0.01% by flow cytometry. In nine of these samples, flow cytometry had a sensitivity of 0.001%, and detected aberrant immunophenotypes in eight samples. Therefore, the two most widely used methods for MRD detection in ALL yield concordant results in the vast majority of cases, although the estimated levels of MRD may vary in some. The use of the two methods in tandem ensures MRD monitoring in all patients.

Adolescent↗

Phytoplankton monitoring by high performance flow cytometry: a successful approach?

BACKGROUND: Regular phytoplankton monitoring in Dutch coastal waters is performed as an indicator of the ecological state of these waters. The monitoring program is focused on temporal and spatial changes of species composition and abundance. Flow cytometry has been introduced to provide additional information, to improve ecosystem understanding, and to increase the efficiency of analysis and reportage. METHODS: Phytoplankton community abundance and composition were routinely determined by flow cytometry and microscopy at six locations in the North Sea over three annual cycles between 2000 and 2003. Supplementary measurements were also made for fluorescence (chlorophyll-a and other pigments) and, in combination with flow cytometric and microscopic data, were used to determine phytoplankton abundance and composition as a function of their size distribution. Real-time imaging of species was also used to identify species on the basis of their flow cytometric optical characteristics. RESULTS: Flow cytometric analysis took 15 min on average. Analysis including data processing, and Web site reportage took less than 1 h. Phytoplankton concentrations (cells/ml), biomass (fluorescence/ml), and concentration of phycoerythrin- or phycocyanin-containing cells (cells/ml) as a function of their algal size were produced every 2 weeks on average. The phytoplankton integrated annual concentration and biomass were used as ecological indicators for overall phytoplankton status. Real-time imaging of cells in flow enabled the identification of dominant species and was applied as an early warning system for Phaeocystis spp. CONCLUSIONS: The reproducibility and count precision due to the large number of observations of the flow cytometric technique provided reliable data for monitoring long-term trends. Flow cytometrically based analyses extended the lower detection limit (<0.5 microm) of analysis beyond the capabilities of other techniques such as the relation between small and larger phytoplankton, the relation between cell counts and biomass as a function of cell size, but also the ability to monitor and report on blooms of harmful algae. A good correlation was found between concentrations (cells/ml) measured by flow cytometry and microscopy. In practice, flow cytometric analysis of a single marine sample took 15 min on average.

Animals↗

Flow cytometry and GFP: a novel assay for measuring the import and turnover of nuclear-encoded mitochondrial proteins in live PC12 cells.

BACKGROUND: Mitochondrial protein import is typically measured by adding radiolabeled precursor proteins to isolated mitochondria. We have developed a novel, high-throughput method for measuring protein import in live differentiated PC12 cells using a tetracycline (Tet) regulated, nuclear encoded, mitochondrially-targeted GFP fusion protein and flow cytometry. METHODS: We generated a PC12 cell line stably transfected with an inducible GFP fusion protein (GFPmt) targeted to mitochondria. GFPmt PC12 cells were treated with NGF for one week to induce neuronal differentiation in the presence of Tet to silence GFP expression. On day seven GFPmt expression was induced by removal of Tet and these "GFP-on" cells were exposed to sublethal levels of CCCP (2 microM) for 24 h. At 24 h, the cells were harvested in Ca(++)-free PBS and the GFPmt signal in live intact cells was measured using flow cytometry. Since GFPmt is not fluorescent prior to being imported into mitochondria, the GFPmt signal reflected only GFPmt imported to mitochondria. PI was used to gate out contributions from dead cells. Turnover of GFPmt in mitochondria was also assessed; in this case, Tet was added to arrest GFPmt expression in GFP-on cells, and the subsequent decline of the fluorescent signal, in the absence of any new GFP synthesis, was measured by flow cytometry. RESULTS: Exposure to 2 microM CCCP for 24 h caused a 61% +/- 0.4 decline in GFPmt fluorescence compared to controls. This decline corresponded to a 30% +/- 7 decrease in GFPmt protein levels measured by Western blot of mitochondrial fractions, and a 72% +/- 5 decline in the import of newly synthesized GFPmt to mitochondria over a 1 h period 24-h after addition of 2 microM CCCP measured by autoradiography. CCCP partially depolarized mitochondria but was not lethal for up to five days. CONCLUSIONS: This novel GFP-based flow cytometry assay is a rapid and sensitive technique for quantifying protein import to mitochondria in live neuronal cells.

Animals↗

Flow cytometry applications in detection and classification of leukemia/lymphoma.

The increase in availability of monoclonal antibodies that specifically react with surface markers on human leukocyte subsets and introduction of more user-friendly clinical flow cytometers have resulted in an evolution of flow cytometry away from a strictly research entity into an important tool in the clinical laboratory. The specific and sensitive detection of leukemia and its differentiation from benign lymphoproliferations is one area in which flow cytometry can substantially impact patient care. The application of immunophenotyping of leukemia/lymphoma using monoclonal antibodies and flow cytometry and the basic science of its instrumentation are presented. Case reviews illustrate the utility of immunophenotyping in making the correct lineage assignment and diagnosis.

Flow Cytometry↗

Comparison of image (CAS 200) and flow cytometry determined DNA content of paraffin-embedded Hodgkin's disease tissue.

To assess the reliability of DNA estimation using image cytometry, deparaffinized lymph nodes from 70 patients with Hodgkin's disease were examined and the results obtained were compared with those from flow cytometry. Image analysis without discriminating between the various cell types, as found in Hodgkin's disease, revealed no separate aneuploid peak. Selecting on morphologically defined nuclear types DNA aneuploidy was detected in 20% of the cases (14/70). The aneuploid populations were limited to the population of nuclei defined as Reed-Sternberg (RS)-like or medium-sized lymphocytes. Benign lymph nodes DNA aneuploidy was not found in any of the controls. Comparison of DNA histograms obtained by image and flow cytometry showed aneuploid peaks using image cytometry in 4 of 30 diploid and 10 of 40 aneuploid flow histograms. In conclusion, image analysis using the CAS 200 system as compared to flow cytometry is more time-consuming and less sensitive to assess ploidy status, although it may provide extra information in some selected cases. Evidence is obtained that DNA aneuploidy in Hodgkin's disease is preferentially expressed by cells with the RS/H-like and medium-sized lymphocyte morphology.

Aneuploidy↗