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Results for “Flow Cytometry”

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PubMed2005

[Detection of minimal residual disease in B lineage acute lymphoblastic leukemia by 4-color flow cytometry].

OBJECTIVE: To evaluate the method and value of detecting bone marrow minimal residual disease (MRD) in B lineage acute lymphoblastic leukemia (B-ALL) by multiparameter flow cytometry (FCM). METHODS: The FCM immunophenotyping of B-lymphocyte precursors in regenerating stage and MRD was analyzed by using two sets of 4-color antibody panels, including mainly CD34, CD10, CD45, CD19, in 26 regenerating bone marrow samples after chemotherapy and 297 consecutive bone marrow specimens from 50 patients with B-ALL, respectively. The immunophenotype of leukemia cells of B-ALL was also detected by four to six antibodies combination of 4-color CD45/SSC gating FCM. The CD19, CD10, CD34 fluorescence intensity of B-cell precursors in normal and leukemic bone marrow was compared by relatively quantitative method. RESULTS: Twelve patients were MRD positive (MRD(+)) among 50 patients during MRD monitoring, the percentages of residual leukemia cells were 0.06% to 7.73%. Eleven cases displayed CD45, CD34, CD19, CD10 antigens aberrant expression. Five patients were bone marrow relapsed and 4 of them were MRD (+) 7-17 weeks before relapse. The percentages of leukemia cells in all the 4 patients were over 0.1%. Only one patient relapsed with MRD negative. The regenerated B precursors could be divided into 3 stages according to the expression of CD45, CD34, CD19, CD10, CD22, and CD20 antigens. Abnormal expression of CD45, CD34, CD19, and CD10 were detected in 71.8% of 213 patients with B-ALL, the percentage of only aberrant expression of CD38 and myeloid antigen was 8.1%. CONCLUSION: Detection of MRD by multiparameter flow cytometry is a rapid, quantitative and sensitive approach, and has a higher predictability for relapse.

Adolescent↗

PubMed2002

Flow cytometry beads rather than the antihuman globulin method should be used to detect HLA Class I IgG antibody (PRA) in cadaveric renal regraft candidates.

HLA Class I antibody screening can be performed by flow cytometry using a mixture of 30 distinct bead populations each coated with the Class I antigen phenotype derived from different cell lines. In this study we compared the efficacy of Class I antibody screens done by flow cytometry beads with the antihuman globulin (AHG) method for patients awaiting cadaveric renal retransplantation. Class I panel reactive antibody (PRA) screening by flow cytometric beads of 21 regraft serum samples that had all been found to be negative by AHG DTT Class I PRA, revealed that 57.1% (12 of 21) had a flow Class I PRA of > or = 10%. Furthermore, when five regraft sera with an intermediate PRA were screened (mean AHG DTT PRA = 33.2 +/- 13%) the mean flow Class I PRA almost doubled (mean flow PRA = 72.4 +/- 10.2%) (p < 0.01). When active UNOS waiting list regraft candidates, after several months of screening the Class I PRA by flow beads, were divided into the three PRA categories based on their peak flow Class I PRA value (0-20%, 21-79% and > or = 80%), the incidence of a positive flow cross-match was 0%, 72% and 85% and the incidence of retransplantation was 60%, 22% and 10%, in each of these groups, respectively. These data provided our histocompatibility laboratory with the rationale to stop performing the AHG PRA and perform only the flow Class I PRA method for regraft candidates.

Coombs Test↗

PubMed1992

Studies of fibrinogen binding to platelets by flow cytometry: an improved method for studies of platelet activation.

Platelet function is dependent upon membrane receptors and their interaction with other proteins. Platelet activation appears to cause a structural change of the glycoprotein IIb/IIIa complex that exposes the fibrinogen binding site, which subsequently binds fibrinogen. Fluorescence-activated flow cytometry (FACS) is an efficient method for studying membrane proteins. Flow cytometry gives single-cell data, allowing the detection of only a small proportion of labelled platelets in whole blood without any washing steps. One problem with this method is that the labelled antibodies and the antigen, if present in plasma, form an immune complex, which may cause false positive reactions due to interaction between mammalian IgG and Fc gamma receptors on the platelets. We show that immune complexes with chicken IgG do not activate human platelets. We have developed a method for measuring platelet-bound fibrinogen in whole blood and platelet-rich plasma utilising fluorescein isothiocyanate (FITC)-conjugated chicken antibodies directed towards human fibrinogen. As low as 1% activated platelets could be detected without interference from Fc-interactions.

Adenosine Diphosphate↗

PubMed1997

Assessment of viability and mitochondrial function of equine spermatozoa using double staining and flow cytometry.

An objective double-staining method was developed to evaluate viability and mitochondrial function of stallion spermatozoa using flow cytometry. Sperm viability was assessed by propidium iodide (PI) exclusion, and mitochondrial function was measured by the intensity of rhodamine 123 (R123) fluorescence. Flow cytometry estimates of sperm viability measured by PI were equivalent (P > 0.05) to estimates made using Hoechst 33258 stain and fluorescent microscopy (% dead: 25 +/- 2.4 vs 21.5 +/- 3.5). The use of both PI and R123 was validated by addition of various proportions of freeze-shocked (membrane damaged) cells to viable spermatozoa. There was a high correlation (r(2) = 0.996) between increased PI positivestained (dead) cells and the number of membrane-damaged spermatozoa added (% dead: 29 +/- 0.4, 44 +/- 1.4, 58 +/- 0.9, 75 +/- 0.7 and 91+/- 0.25 vs 0, 25, 50, 75 and 100% damaged cells, respectively). Optimal mitochondrial activity (OMA), as assessed by R123 uptake, was also reduced proportionally (r(2) = 0.976) by the percentage of membrane-damaged cells added (% OMA: 48 +/- 0.6, 37 +/- 1.7, 29 +/- 0.5, 16 +/- 1, 3.8 +/- 1.3 vs 0, 25, 50, 75 and 100% damaged cells, respectively). The mitochondrial inhibitors rotenone and monensin significantly depressed optimal mitochondrial activity (P < 0.001), and there was a significant positive correlation (r(2) = 0.959) between the dose of inhibitors added and the population of sperm cells exhibiting minimal R123 staining (4 -/+ 0.9, 12 -/+ 1.6, 14 -/+ 0.1 and 28 -/+ 2% for treatments with 0, 0.5, 1 and 2 x 10(-5) M rotenone and 0, 0.5, 1, and 2 x 10(-4) M monensin, respectively). Finally, it was shown that treatments containing identical proportions of membrane-damaged cells yielded similar results in terms of viability and mitochondrial activity, irrespective of whether the staining procedure was single or double (P > 0.05). The results of the double-staining method revealed that the percentage of spermatozoa with optimally functioning mitochondria was significantly correlated with the percentage of viable (PI negative) sperm cells (r(2) = 0.998). Flow cytometric analyses using this staining procedure provides reliable and rapid (10,000 cells/min) qualitative assessment of stallion semen.

Journal Article↗

PubMed1999

Detection of Cryptosporidium parvum in horses: thresholds of acid-fast stain, immunofluorescence assay, and flow cytometry.

Feces collected from three asymptomatic horses and seeded with Cryptosporidium parvum oocysts (10(1) to 10(6)/g of feces) were evaluated by acid-fast staining (AF), an immunofluorescent antibody (IFA) technique, and flow cytometry. The thresholds of detection were 5 x 10(5) oocysts/g of feces for the IFA and AF techniques and 5 x 10(4) oocysts/g for flow cytometry.

Animals↗

PubMed1987

Quantitation of the binding, uptake, and degradation of fluoresceinylated neoglycoproteins by flow cytometry.

The fluorescence properties of the fluorescein residues bound to a protein are used to analyze by flow cytometry the neoglycoproteins' endocytosis mediated by membrane lectins of Lewis lung carcinoma cells (3LL cells). The quantum yield of fluorescein bound to a protein is dependent on the number of fluorophore molecules bound to a protein molecule and the pH of the environmental medium. The mean fluorescence intensity of a fluorescein molecule bound to a protein decreases when the number of fluorescein residues per protein molecule increases. However, after proteolytic digestion, the mean fluorescence intensity of a fluorescein molecule is constant and equal to that of free fluorescein. The binding of fluorescein-labeled alpha-glucosylated serum albumin to 3LL cells at 4 degrees C can easily be determined by flow cytometry because under these conditions the environmental pH is neutral, and the neoglycoprotein is not degraded. When the cells are incubated at 37 degrees C in the presence of a fluorescein-labeled neoglycoprotein, the fluorescence intensity of a cell is low because of the low pH of endosomes and lysosomes but is increased upon a postincubation at 4 degrees C in the presence of monensin, a proton/sodium ionophore. The extent of the proteolytic digestion of an endocytosed neoglycoprotein can be assessed by comparing, upon a monensin postincubation at 4 degrees C, the high cell-associated fluorescence of cells incubated in the absence of leupeptin (an inhibitor of lysosomal proteases) and the relatively low fluorescence intensity of cells incubated in the presence of leupeptin.

Animals↗

PubMed2000

Analysis of bacterial function by multi-colour fluorescence flow cytometry and single cell sorting.

With the increased awareness of the problems associated with the growth dependent analysis of bacterial populations, direct optical detection methods such as flow cytometry have enjoyed increased popularity over the last few years. Among the analyses discussed here are: (1) Bacterial discrimination from other particles on the basis of nucleic acid staining, using sample disaggregation to provide fast reliable enumeration while minimizing data artefacts due to post sampling growth; (2) Determination of basic cell functions such as reproductive ability, metabolic activity and membrane integrity, to characterise the physiological state or degree of viability of bacteria; and (3) The use of single cell sorting onto agar plates, microscope slides or into multi-well plates to correlate viability as determined by cell growth with fluorescent labelling techniques. Simultaneous staining with different fluorochromes provides an extremely powerful way to demonstrate culture heterogeneity, and also to understand the functional differences revealed by each stain in practical applications. Analysis of bacterial fermentations showed a considerable drop (20%) in membrane potential and integrity during the latter stages of small scale (5L), well mixed fed-batch fermentations. These changes, not found in either batch or continuous culture fermentations, are probably due to the severe, steadily increasing stress associated with glucose limitation during the fed-batch process, suggesting 'on-line' flow cytometry could improve process control. Heat injured cells can already show up to 4 log of differences in recovery in different pre-enrichment media, thus contributing to the problem of viable but non-culturable cells (VBNC's). Cytometric cell sorting demonstrated decreasing recovery with increasing loss of membrane function. However, a new medium protecting the cells from intracellular and extracellular causes of oxidative stress improved recovery considerably. Actively respiring cells showed much higher recovery improvement than the other populations, demonstrating for the first time the contribution of oxidative respiration to intracellular causes of damage as a key part of the VBNC problem. Finally, absolute and relative frequencies of one species in a complex population were determined using immunofluorescent labelling in combination with the analysis of cell function. The detail and precision of multiparameter flow cytometric measurements of cell function at the single cell level now raise questions regarding the validity of classical, growth dependent viability assessment methods.

Bacteria↗

PubMed1997

Limits of flow-cytometry histogram analysis methods to assess bladder tumour antigen expression.

Tumour-associated antigens detected in cells obtained from bladder washings or tumours are useful markers in bladder cancer. Flow cytometry is commonly used to quantify immuno-stained cells. A straightforward way to analyze data is to count the fluorescent cells above a threshold empirically determined on a control histogram representation. However, specific antigens expressed at highly variable rates give rise to wide range distributions in flow cytometry as illustrated when a mucin antigen for urinary bladder was titrated by M344 monoclonal antibody in urothelial cancer cells. We have evaluated several methods of background estimation and subtraction in order to determine the proportion of M344 Mab positive cells. These include threshold setting (Histogram Shape Dependent (HSD) threshold developed in this study, 2% preset or 5% preset background), subtraction of the blank from the test histograms, and Kolmogorov-Smirnov statistical test. The HSD method appeared to be a more reliable method for background estimation; however, in the case of very low antigen expression, where specific fluorescence histograms could hardly be distinguished from that of the background, fluorescence microscopy remained the only valid method, since it allowed the distinction between specific and non-specific fluorescence on the basis of structural differences between the two.

Antibodies, Monoclonal↗

PubMed1998

Flow cytometry analysis of cell cycle in myosin II-deficient yeast.

OBJECTIVE: To determine whether cell cycle changes can be detected in myosin II-deficient cells using flow cytometry techniques. BACKGROUND: Although the primary role of myosin II (Myo1p) in the yeast Saccharomyces cerevisiae is in cytokinesis we have reported that this conventional myosin also appears to influence the regulation of cell wall metabolism as indicated by increases in the expression of chitin metabolizing enzymes in a null mutant of the MYO1 gene. The expression of these enzymes is known to be regulated in the cell cycle suggesting that cell cycle changes may alter their expression. METHODS: Flow cytometry was employed to assess the nuclear DNA content of logarithmic yeast cell cultures as a means of determining changes in the cell cycle of Myo1p-deficient cells. RESULTS: Significant changes were observed in the Myo1p-deficient strain suggesting that these cells are arrested in G2/M-phase of the cell cycle. CONCLUSIONS: Based on the results of this preliminary study, we propose a model in which the increased activity of chitin metabolizing enzymes may be explained by a mitotic arrest in these cells.

Cell Culture Techniques↗

PubMed2000

Gap-junctional coupling measured by flow cytometry.

A method is described which reliably quantifies the degree of intercellular communication via gap junctions by combining a dye-loading technique with fluorescence-activated flow cytometry. Our experiments expand former measurements of other groups by analyzing the time- and density-dependent onset of coupling with a fixed ratio of donor to recipient cells. The high sensitivity of this technique provides a better resolution than the microelectrode technique and allows the detection of small changes in gap-junctional coupling by examining a large number of cells in a single experiment. Suspended cells were loaded with the membrane-permeable dye calcein AM, which is intracellularly hydrolyzed by nonspecific esterases, and the resulting polyanionic calcein is thus trapped inside these donor cells. Gap junctions, however, are permeable for this fluorescent dye, as can be observed when suspended donor cells are added to recipient cells (i.e., monolayer cultures) in which case cell-cell contact is established within less than 60 min. In addition, one of these two cell populations can also be stained with a membrane-resident dye (e.g., DiI), which facilitates the identification of different cell populations (donors, recipients, and noncoupled cells) not only by epifluorescence microscopy but also by flow cytometry. Our analyses reveal that junctional coupling depends not only on the connexin type (homo- or heterotypic junction) but also on the origin (species) of the contacting cells (homo- or heterospecific contact). We confirm earlier reports in which homotypic-homospecific coupling was demonstrated with different techniques in connexin-transfected HeLa and RIN cells as well as in BICR/M1R(k) and 3T3/SV40 cells. In contrast to other publications, we show that a significant heterotypic-homospecific coupling between Cx40- and Cx43-HeLa transfectants can be resolved, whereas no coupling was detected for heterotypic-heterospecific contacts between Cx40-HeLa transfectants and the Cx43-expressing cell lines BICR/M1R(k), 3T3/SV40, and RIN.

3T3 Cells↗

PubMed1990

Determination of mixed chimerism by a simple flow cytometry method.

A simple, sensitive and accurate method was developed to determine the level of lymphoid chimerism in bone marrow-transplanted rodents. The method is based on flow cytometry using polyclonal alloantisera and labeled second step anti-IgG antibodies. Using mixtures of spleen cells from different mouse strains, it was demonstrated that low levels of chimeric cells (less than 1%) could easily be detected. Moreover, using two-color fluorescence analysis, the level of chimerism could also be determined in subpopulations of lymphoid cells, e.g., CD4 or CD8 cells and was found to be identical to the results obtained in unseparated lymphoid populations. The method was compared to the complement dependent cytotoxicity assay (CDCA) and to the flow cytometric determination of chimerism using labeled monoclonal antibodies against specific MHC antigens. CDCA was found to be more labor intensive and could only estimate the composition of the cell mixtures without detecting low levels of chimerism (less than 5%). The results of flow cytometry, using directly labeled monoclonal antibodies or polyclonal antibodies with second step reagents, were identical. It is concluded that, due to its simplicity and high sensitivity, the method described permits reliable determination of the level of mixed chimerism in rodents and is an excellent alternative when no anti-MHC mAbs are available.

Animals↗

PubMed1988

Analysis of tumor heterogeneity in a patient with synchronously occurring female genital tract malignancies by DNA flow cytometry, DNA fingerprinting, and immunohistochemistry.

A case of a patient with bilateral ovarian cancer and a uterine malignant mesodermal mixed tumor with ascites and metastatic disease is presented. Flow cytometry, DNA fingerprinting, and immunohistochemistry were performed to assess the origin of these malignancies. Ploidy analysis showed that both ovarian tumors had different aneuploid stemlines (DNA index [DI] = 1.64, 1.85, right ovary and DI = 1.73, left ovary) indicating independent origins. One of the stemlines in the right ovary (DI = 1.64) was also present in the ascites cells, whereas omentum metastases showed the same stemline (DI = 1.73) as the left ovarian tumor. The uterine malignancy contained three aneuploid stemlines. The highest stemline was associated with epithelial differentiation, but a metastatic origin from the left ovarian tumor seems unlikely. DNA fingerprinting analysis revealed a common change in restriction fragment length pattern in the DNA from all tumor localizations as compared with the patient's constitutional DNA. These results indicate that DNA flow cytometry can be helpful in discriminating intragenital metastatic disease from multiple primary tumors.

Aged↗

PubMed1990

DNA flow cytometry of myocardial cell nuclei in paraffin-embedded, human autopsy, cardiac tissue.

Changes in nuclear DNA occur in myocytes as they grow and hypertrophy. We used DNA flow cytometry to study myocardial nuclei from paraffin-embedded human autopsy tissue. Forty hearts ranging from 310-1040 g were studied. Histograms generated for each heart showed peaks at the 2N and 4N positions. Two of 9 hearts weighing 310-430 g had 8N peaks as well. Fourteen of 17 hearts weighing 450-690 g also had 8N peaks but no 16N peaks. Twelve of 14 hearts weighing 710 to 1040 g had 8N peaks and 4 had 16N peaks as well. Contingency analysis showed statistically significant differences in the ploidy of nuclei from the three different groups of hearts. This study corroborates previous work indicating that DNA ploidy in myocardium increases with hypertrophy. Thus, flow cytometry of paraffin-embedded myocardium should be a useful technique to study DNA from archival material, obviating the need for fresh or frozen tissue.

Cardiomegaly↗

PubMed1998

Mitochondrial membrane potential and DNA stainability in human sperm cells: a flow cytometry analysis with implications for male infertility.

Sperm cells from control donors of proven fertility and men from barren couples were studied by conventional procedures, i.e., light microscopy as well as flow cytometry. Light microscopy analysis of semen included the measurement of spermatozoa concentration, morphology, and motility. All the men from barren couples were asthenozoospermic at the conventional analysis of semen samples. Flow cytometry was applied to study two important parameters of sperm cells: mitochondrial membrane potential (MMP) assessed by the cationic dye JC-1 and DNA stainability with propidium iodide (PI). JC-1 staining was more reliable than the classical procedure used for this purpose, i.e., rhodamine 123 (Rh123) staining, and allowed us to show a positive correlation between MMP and spermatozoa motility. Regarding DNA analysis, a higher relative percentage of immature spermatozoa, showing a high accessibility of DNA to the intercalating PI fluorochrome, was found in men from barren couples compared to donors of proven fertility. The relative percentage of immature spermatozoa was significantly higher in semen from oligoasthenozoospermic subjects. Moreover, a positive correlation was found between immature spermatozoa, as evaluated by PI staining, and cells with depolarized mitochondria, as evaluated by JC-1 staining, suggesting that spermatozoa defective for nuclear maturity could be functionally defective cells. No correlation between immature spermatozoa determined by FCM and immature spermatozoa determined by light microscopy was found, suggesting that these two techniques assess sperm cell maturity at different levels.

Adult↗

PubMed1997

Epstein-Barr virus suspension cell assay using in situ hybridization and flow cytometry.

We have developed a procedure for quantitative assay of Epstein-Barr virus (EBV)-infected cells in suspension in either latent or replicative phase using in situ hybridization and flow cytometry. The cells were hybridized with EBV-specific digoxigenin or biotin-labeled oligonucleotide probes, followed by binding to fluorescein-conjugated anti-digoxigenin or phycoerythrin-conjugated streptavidin, respectively. The cells hybridizing to the specific probes were quantitated by flow cytometry. A strong shift in fluorescence intensity (20-fold) was observed when the EBV-positive culture cells were hybridized with a specific EBER1 antisense probe. The sensitivity of the assay was at least one positive cell out of 9,000 beyond the normal control mean +/- 2 S.D. We performed two-color in situ hybridization/flow cytometry using probes to an EBV replication phase-specific mRNA and EBER1 on B95-8 cells in which a small portion (2-4%) of cells induce spontaneously into the replicative phase. In addition, we have developed a method for simultaneous analysis of the cell surface phenotype and EBV nucleic acid content in individual cells.

Cell Separation↗

PubMed2006

Comparison of two alternative methods for CD4+ T-cell determination (Coulter manual CD4 count and CyFlow) against standard dual platform flow cytometry in Uganda.

BACKGROUND: In this study we evaluated alternative CD4(+) T-cell counting methods in clients of a PMTCT Programme in rural Uganda. METHODS: The Coulter Manual CD4 Count method for CD4(+) T-cell enumeration (Cyto-Spheres) and an automated method (volumetric, single-platform flow cytometry; CyFlow) were compared with a standard, dual-platform flow cytometry protocol (DPFC, FACScan). RESULTS: Correlation and precision of agreement were higher for the CyFlow method (r = 0.929 and eta = 0.08) when compared to DPFC than for the Cyto-Spheres method (r = 0.725 and eta = 0.3). Multiple linear regression analysis showed that CD4(+) cell counts by the CyFlow method were a stronger predictor for results of DPFC than those of the Cyto-Spheres method (r(2) = 0.864 and r(2) = 0.552, respectively). When compared to DPFC the CyFlow method generated higher CD4(+) cell counts than the Cyto-Spheres method, as expressed by a higher median and mean difference (+70 and +90 cells for CyFlow, +28 and -1.4 cells for Cyto-Spheres). CONCLUSION: Both, the manual Cyto-Spheres method and the CyFlow method can be used for the enumeration of CD4(+) cells in resource-limited settings. Under supervised conditions, the CyFlow method produced results more consistent with the reference method than the Cyto-Spheres method.

Algorithms↗

PubMed1994

A comparative study of flow cytometry and histopathologic findings in thyroid follicular carcinomas and adenomas.

As a possible diagnostic aid in the often difficult histopathologic distinction of thyroid follicular carcinomas from adenomas based on invasion most flow cytometry studies have indicated a higher aneuploidy incidence in carcinomas. However, these reports often are difficult to analyze mainly due to nonuniformity of pathologic diagnostic criteria. The present study compares the flow cytometry results of 65 follicular tumors with pathologic findings based on the World Health Organization's specific diagnostic and staging criteria. Aneuploidy was significantly higher in the 28 cancers than in the 27 hypercellular (fetal and embryonal) adenomas (57% v 22%; P = .02). There was a high percentage of aneuploidy (75%; nine of 12 cases) in the widely invasive follicular carcinomas, compared with 40% (six of 15 cases) in the minimally invasive carcinomas, 22% (six of 27 cases) in the hypercellular adenomas, and 10% (one of 10 cases) in the normofollicular or macrofollicular adenomas. However, aneuploidy was not significantly different between the most difficult differential histopathologic diagnoses of minimally invasive follicular carcinoma (40%; six of 15 cases) and hypercellular adenoma (22%; six of 27 cases) (P = .12). Other data included relatively high frequencies of aneuploidy in hypercellular adenomas (29%; six of 21 cases) and diploid status of carcinomas (36%; 12 of 33 cases). In summary, although the overall findings show a trend toward increasing aneuploidy from well-differentiated and hypercellular adenomas to minimally and widely invasive follicular carcinomas, the aneuploidy data are inconsistent and indicative of its nonspecificity and limited diagnostic usefulness.

Adenocarcinoma, Follicular↗

PubMed1995

p53 expression measured by flow cytometry. A comparison of three monoclonal antibodies and the relationship with grade and DNA ploidy in breast cancer.

The aim of this study was to quantify p53 expression by flow cytometry. A panel of three monoclonal antibodies: NCL-p53-240, NCL-p53-1801 and NCL-p53-DO7, was tested on breast cell lines and primary breast cancers. The relationships between ploidy, tumour grade and p53 expression for each antibody, were examined. Methodology was assessed using a variety of breast cell lines. Staining patterns were confirmed and the quantification technique qualified. Cytokeratin-positive cells from 58 samples obtained from patients with breast cancer were assayed for DNA content and p53 expression. p53 quantification was performed using calibrated fluorescent beads on cytokeratin-positive cells. Bloom and Richardson grading revealed 20 grade I and 38 grade II/III breast cancers. Examination of fluorescence thresholds showed a positive correlation between grade and DO7 (P = 0.003) at a level of 8900 molecules, 240 (P = 0.005) at a level of 2900 molecules and 1801 (P = 0.005) at a level of 1850 molecules. These levels equated with 34% (DO7), 43% (240) and 43% (1801) of the samples being classified as p53-positive. Examination of ploidy revealed 23 diploid and 35 aneuploid breast cancers. Application of p53 threshold levels on diploid and aneuploid tumours showed correlation between aneuploidy and p53 expression for DO7 at a level of 9000 molecules, 240 at a level of 1900 molecules and 1801 at a level of 1800 molecules. These levels equated with 34% (DO7), 52% (240) and 52% (1801) of the samples being classified as p53-positive. We conclude that measurement of p53 by flow cytometry may be of clinical importance by indicating levels of positivity using fluorescence thresholds. p53 expression has been shown to correlate with both grade and ploidy. Flow-cytometric measurement of p53 may be a useful prognostic assay.

Aneuploidy↗